Move to the src/ layout, and make greenlet a package.issue184

Make 'tests' become 'greenlet.tests', and be compatible with 'python -m unittest discover'.

Fixes #184. Fixes #184. Fixes #189.

44 files changed, 5623 insertions, 0 deletions

diff --git a/src/greenlet/__init__.py b/src/greenlet/__init__.py
new file mode 100644
index 0000000..7e9142f
--- /dev/null
+++ b/src/greenlet/__init__.py
@@ -0,0 +1,16 @@
+# -*- coding: utf-8 -*-
+"""
+The root of the greenlet package.
+"""
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+# TODO: Define a correct __all__
+# pylint:disable=unused-import
+# TODO: Move the definition of __version__ here, instead of the
+# C code. zest.releaser will find it here, but not in C.
+
+from ._greenlet import * # pylint:disable=wildcard-import
+from ._greenlet import __version__
+from ._greenlet import _C_API # pylint:disable=no-name-in-module
diff --git a/src/greenlet/greenlet.c b/src/greenlet/greenlet.c
new file mode 100644
index 0000000..895931d
--- /dev/null
+++ b/src/greenlet/greenlet.c
@@ -0,0 +1,1871 @@
+/* vim:set noet ts=8 sw=8 : */
+
+#define GREENLET_MODULE
+
+#include "greenlet.h"
+#include "structmember.h"
+
+
+/***********************************************************
+
+A PyGreenlet is a range of C stack addresses that must be
+saved and restored in such a way that the full range of the
+stack contains valid data when we switch to it.
+
+Stack layout for a greenlet:
+
+               |     ^^^       |
+               |  older data   |
+               |               |
+  stack_stop . |_______________|
+        .      |               |
+        .      | greenlet data |
+        .      |   in stack    |
+        .    * |_______________| . .  _____________  stack_copy + stack_saved
+        .      |               |     |             |
+        .      |     data      |     |greenlet data|
+        .      |   unrelated   |     |    saved    |
+        .      |      to       |     |   in heap   |
+ stack_start . |     this      | . . |_____________| stack_copy
+               |   greenlet    |
+               |               |
+               |  newer data   |
+               |     vvv       |
+
+
+Note that a greenlet's stack data is typically partly at its correct
+place in the stack, and partly saved away in the heap, but always in
+the above configuration: two blocks, the more recent one in the heap
+and the older one still in the stack (either block may be empty).
+
+Greenlets are chained: each points to the previous greenlet, which is
+the one that owns the data currently in the C stack above my
+stack_stop.  The currently running greenlet is the first element of
+this chain.  The main (initial) greenlet is the last one.  Greenlets
+whose stack is entirely in the heap can be skipped from the chain.
+
+The chain is not related to execution order, but only to the order
+in which bits of C stack happen to belong to greenlets at a particular
+point in time.
+
+The main greenlet doesn't have a stack_stop: it is responsible for the
+complete rest of the C stack, and we don't know where it begins.  We
+use (char*) -1, the largest possible address.
+
+States:
+  stack_stop == NULL && stack_start == NULL:  did not start yet
+  stack_stop != NULL && stack_start == NULL:  already finished
+  stack_stop != NULL && stack_start != NULL:  active
+
+The running greenlet's stack_start is undefined but not NULL.
+
+ ***********************************************************/
+
+/*** global state ***/
+
+/* In the presence of multithreading, this is a bit tricky:
+
+   - ts_current always store a reference to a greenlet, but it is
+     not really the current greenlet after a thread switch occurred.
+
+   - each *running* greenlet uses its run_info field to know which
+     thread it is attached to.  A greenlet can only run in the thread
+     where it was created.  This run_info is a ref to tstate->dict.
+
+   - the thread state dict is used to save and restore ts_current,
+     using the dictionary key 'ts_curkey'.
+*/
+
+extern PyTypeObject PyGreenlet_Type;
+
+/* Defines that customize greenlet module behaviour */
+#ifndef GREENLET_USE_GC
+#define GREENLET_USE_GC 1
+#endif
+
+#ifndef GREENLET_USE_TRACING
+#define GREENLET_USE_TRACING 1
+#endif
+
+#ifndef Py_SET_REFCNT
+   /* Py_REFCNT and Py_SIZE macros are converted to functions
+   https://bugs.python.org/issue39573 */
+  #define Py_SET_REFCNT(obj, refcnt) Py_REFCNT(obj) = (refcnt)
+#endif
+
+#ifndef _Py_DEC_REFTOTAL
+  /* _Py_DEC_REFTOTAL macro has been removed from Python 3.9 by:
+    https://github.com/python/cpython/commit/49932fec62c616ec88da52642339d83ae719e924 */
+#  ifdef Py_REF_DEBUG
+#    define _Py_DEC_REFTOTAL _Py_RefTotal--
+#  else
+#    define _Py_DEC_REFTOTAL
+#  endif
+#endif
+
+/* Weak reference to the switching-to greenlet during the slp switch */
+static PyGreenlet* volatile ts_target = NULL;
+/* Strong reference to the switching from greenlet after the switch */
+static PyGreenlet* volatile ts_origin = NULL;
+/* Strong reference to the current greenlet in this thread state */
+static PyGreenlet* volatile ts_current = NULL;
+/* NULL if error, otherwise args tuple to pass around during slp switch */
+static PyObject* volatile ts_passaround_args = NULL;
+static PyObject* volatile ts_passaround_kwargs = NULL;
+
+/***********************************************************/
+/* Thread-aware routines, switching global variables when needed */
+
+#define STATE_OK    (ts_current->run_info == PyThreadState_GET()->dict \
+                     || !green_updatecurrent())
+
+static PyObject* ts_curkey;
+static PyObject* ts_delkey;
+#if GREENLET_USE_TRACING
+static PyObject* ts_tracekey;
+static PyObject* ts_event_switch;
+static PyObject* ts_event_throw;
+#endif
+static PyObject* PyExc_GreenletError;
+static PyObject* PyExc_GreenletExit;
+static PyObject* ts_empty_tuple;
+static PyObject* ts_empty_dict;
+
+#if GREENLET_USE_GC
+#define GREENLET_GC_FLAGS Py_TPFLAGS_HAVE_GC
+#define GREENLET_tp_alloc PyType_GenericAlloc
+#define GREENLET_tp_free PyObject_GC_Del
+#define GREENLET_tp_traverse green_traverse
+#define GREENLET_tp_clear green_clear
+#define GREENLET_tp_is_gc green_is_gc
+#else /* GREENLET_USE_GC */
+#define GREENLET_GC_FLAGS 0
+#define GREENLET_tp_alloc 0
+#define GREENLET_tp_free 0
+#define GREENLET_tp_traverse 0
+#define GREENLET_tp_clear 0
+#define GREENLET_tp_is_gc 0
+#endif /* !GREENLET_USE_GC */
+
+static void green_clear_exc(PyGreenlet* g)
+{
+#ifdef GREENLET_USE_EXC_INFO
+	g->exc_info = NULL;
+	g->exc_state.exc_type = NULL;
+	g->exc_state.exc_value = NULL;
+	g->exc_state.exc_traceback = NULL;
+	g->exc_state.previous_item = NULL;
+#else
+	g->exc_type = NULL;
+	g->exc_value = NULL;
+	g->exc_traceback = NULL;
+#endif
+}
+
+static PyGreenlet* green_create_main(void)
+{
+	PyGreenlet* gmain;
+	PyObject* dict = PyThreadState_GetDict();
+	if (dict == NULL) {
+		if (!PyErr_Occurred())
+			PyErr_NoMemory();
+		return NULL;
+	}
+
+	/* create the main greenlet for this thread */
+	gmain = (PyGreenlet*) PyType_GenericAlloc(&PyGreenlet_Type, 0);
+	if (gmain == NULL)
+		return NULL;
+	gmain->stack_start = (char*) 1;
+	gmain->stack_stop = (char*) -1;
+	gmain->run_info = dict;
+	Py_INCREF(dict);
+	return gmain;
+}
+
+static int green_updatecurrent(void)
+{
+	PyObject *exc, *val, *tb;
+	PyThreadState* tstate;
+	PyGreenlet* current;
+	PyGreenlet* previous;
+	PyObject* deleteme;
+
+green_updatecurrent_restart:
+	/* save current exception */
+	PyErr_Fetch(&exc, &val, &tb);
+
+	/* get ts_current from the active tstate */
+	tstate = PyThreadState_GET();
+	if (tstate->dict && (current =
+	    (PyGreenlet*) PyDict_GetItem(tstate->dict, ts_curkey))) {
+		/* found -- remove it, to avoid keeping a ref */
+		Py_INCREF(current);
+		PyDict_DelItem(tstate->dict, ts_curkey);
+	}
+	else {
+		/* first time we see this tstate */
+		current = green_create_main();
+		if (current == NULL) {
+			Py_XDECREF(exc);
+			Py_XDECREF(val);
+			Py_XDECREF(tb);
+			return -1;
+		}
+	}
+	assert(current->run_info == tstate->dict);
+
+green_updatecurrent_retry:
+	/* update ts_current as soon as possible, in case of nested switches */
+	Py_INCREF(current);
+	previous = ts_current;
+	ts_current = current;
+
+	/* save ts_current as the current greenlet of its own thread */
+	if (PyDict_SetItem(previous->run_info, ts_curkey, (PyObject*) previous)) {
+		Py_DECREF(previous);
+		Py_DECREF(current);
+		Py_XDECREF(exc);
+		Py_XDECREF(val);
+		Py_XDECREF(tb);
+		return -1;
+	}
+	Py_DECREF(previous);
+
+	/* green_dealloc() cannot delete greenlets from other threads, so
+	   it stores them in the thread dict; delete them now. */
+	deleteme = PyDict_GetItem(tstate->dict, ts_delkey);
+	if (deleteme != NULL) {
+		PyList_SetSlice(deleteme, 0, INT_MAX, NULL);
+	}
+
+	if (ts_current != current) {
+		/* some Python code executed above and there was a thread switch,
+		 * so ts_current points to some other thread again. We need to
+		 * delete ts_curkey (it's likely there) and retry. */
+		PyDict_DelItem(tstate->dict, ts_curkey);
+		goto green_updatecurrent_retry;
+	}
+
+	/* release an extra reference */
+	Py_DECREF(current);
+
+	/* restore current exception */
+	PyErr_Restore(exc, val, tb);
+
+	/* thread switch could happen during PyErr_Restore, in that
+	   case there's nothing to do except restart from scratch. */
+	if (ts_current->run_info != tstate->dict)
+		goto green_updatecurrent_restart;
+
+	return 0;
+}
+
+static PyObject* green_statedict(PyGreenlet* g)
+{
+	while (!PyGreenlet_STARTED(g)) {
+		g = g->parent;
+		if (g == NULL) {
+			/* garbage collected greenlet in chain */
+			return NULL;
+		}
+	}
+	return g->run_info;
+}
+
+/***********************************************************/
+
+/* Some functions must not be inlined:
+   * slp_restore_state, when inlined into slp_switch might cause
+     it to restore stack over its own local variables
+   * slp_save_state, when inlined would add its own local
+     variables to the saved stack, wasting space
+   * slp_switch, cannot be inlined for obvious reasons
+   * g_initialstub, when inlined would receive a pointer into its
+     own stack frame, leading to incomplete stack save/restore
+*/
+
+#if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4))
+#define GREENLET_NOINLINE_SUPPORTED
+#define GREENLET_NOINLINE(name) __attribute__((noinline)) name
+#elif defined(_MSC_VER) && (_MSC_VER >= 1300)
+#define GREENLET_NOINLINE_SUPPORTED
+#define GREENLET_NOINLINE(name) __declspec(noinline) name
+#endif
+
+#ifdef GREENLET_NOINLINE_SUPPORTED
+/* add forward declarations */
+static void GREENLET_NOINLINE(slp_restore_state)(void);
+static int GREENLET_NOINLINE(slp_save_state)(char*);
+#if !(defined(MS_WIN64) && defined(_M_X64))
+static int GREENLET_NOINLINE(slp_switch)(void);
+#endif
+static int GREENLET_NOINLINE(g_initialstub)(void*);
+#define GREENLET_NOINLINE_INIT() do {} while(0)
+#else
+/* force compiler to call functions via pointers */
+static void (*slp_restore_state)(void);
+static int (*slp_save_state)(char*);
+static int (*slp_switch)(void);
+static int (*g_initialstub)(void*);
+#define GREENLET_NOINLINE(name) cannot_inline_ ## name
+#define GREENLET_NOINLINE_INIT() do { \
+	slp_restore_state = GREENLET_NOINLINE(slp_restore_state); \
+	slp_save_state = GREENLET_NOINLINE(slp_save_state); \
+	slp_switch = GREENLET_NOINLINE(slp_switch); \
+	g_initialstub = GREENLET_NOINLINE(g_initialstub); \
+} while(0)
+#endif
+
+/*
+ * the following macros are spliced into the OS/compiler
+ * specific code, in order to simplify maintenance.
+ */
+
+#define SLP_SAVE_STATE(stackref, stsizediff)            \
+	stackref += STACK_MAGIC;                        \
+	if (slp_save_state((char*)stackref)) return -1; \
+	if (!PyGreenlet_ACTIVE(ts_target)) return 1;    \
+	stsizediff = ts_target->stack_start - (char*)stackref
+
+#define SLP_RESTORE_STATE()                             \
+	slp_restore_state()
+
+
+#define SLP_EVAL
+#define slp_switch GREENLET_NOINLINE(slp_switch)
+#include "slp_platformselect.h"
+#undef slp_switch
+
+#ifndef STACK_MAGIC
+#error "greenlet needs to be ported to this platform, or taught how to detect your compiler properly."
+#endif /* !STACK_MAGIC */
+
+#ifdef EXTERNAL_ASM
+/* CCP addition: Make these functions, to be called from assembler.
+ * The token include file for the given platform should enable the
+ * EXTERNAL_ASM define so that this is included.
+ */
+
+intptr_t slp_save_state_asm(intptr_t *ref) {
+	intptr_t diff;
+	SLP_SAVE_STATE(ref, diff);
+	return diff;
+}
+
+void slp_restore_state_asm(void) {
+	SLP_RESTORE_STATE();
+}
+
+extern int slp_switch(void);
+
+#endif
+
+/***********************************************************/
+
+static int g_save(PyGreenlet* g, char* stop)
+{
+	/* Save more of g's stack into the heap -- at least up to 'stop'
+
+	   g->stack_stop |________|
+	                 |        |
+	                 |    __ stop       . . . . .
+	                 |        |    ==>  .       .
+	                 |________|          _______
+	                 |        |         |       |
+	                 |        |         |       |
+	  g->stack_start |        |         |_______| g->stack_copy
+
+	 */
+	intptr_t sz1 = g->stack_saved;
+	intptr_t sz2 = stop - g->stack_start;
+	assert(g->stack_start != NULL);
+	if (sz2 > sz1) {
+		char* c = (char*)PyMem_Realloc(g->stack_copy, sz2);
+		if (!c) {
+			PyErr_NoMemory();
+			return -1;
+		}
+		memcpy(c+sz1, g->stack_start+sz1, sz2-sz1);
+		g->stack_copy = c;
+		g->stack_saved = sz2;
+	}
+	return 0;
+}
+
+static void GREENLET_NOINLINE(slp_restore_state)(void)
+{
+	PyGreenlet* g = ts_target;
+	PyGreenlet* owner = ts_current;
+
+#ifdef SLP_BEFORE_RESTORE_STATE
+	SLP_BEFORE_RESTORE_STATE();
+#endif
+
+	/* Restore the heap copy back into the C stack */
+	if (g->stack_saved != 0) {
+		memcpy(g->stack_start, g->stack_copy, g->stack_saved);
+		PyMem_Free(g->stack_copy);
+		g->stack_copy = NULL;
+		g->stack_saved = 0;
+	}
+	if (owner->stack_start == NULL)
+		owner = owner->stack_prev; /* greenlet is dying, skip it */
+	while (owner && owner->stack_stop <= g->stack_stop)
+		owner = owner->stack_prev; /* find greenlet with more stack */
+	g->stack_prev = owner;
+}
+
+static int GREENLET_NOINLINE(slp_save_state)(char* stackref)
+{
+	/* must free all the C stack up to target_stop */
+	char* target_stop = ts_target->stack_stop;
+	PyGreenlet* owner = ts_current;
+	assert(owner->stack_saved == 0);
+	if (owner->stack_start == NULL)
+		owner = owner->stack_prev;  /* not saved if dying */
+	else
+		owner->stack_start = stackref;
+
+#ifdef SLP_BEFORE_SAVE_STATE
+	SLP_BEFORE_SAVE_STATE();
+#endif
+
+	while (owner->stack_stop < target_stop) {
+		/* ts_current is entierely within the area to free */
+		if (g_save(owner, owner->stack_stop))
+			return -1;  /* XXX */
+		owner = owner->stack_prev;
+	}
+	if (owner != ts_target) {
+		if (g_save(owner, target_stop))
+			return -1;  /* XXX */
+	}
+	return 0;
+}
+
+static int g_switchstack(void)
+{
+	/* Perform a stack switch according to some global variables
+	   that must be set before:
+	   - ts_current: current greenlet (holds a reference)
+	   - ts_target: greenlet to switch to (weak reference)
+	   - ts_passaround_args: NULL if PyErr_Occurred(),
+	       else a tuple of args sent to ts_target (holds a reference)
+	   - ts_passaround_kwargs: switch kwargs (holds a reference)
+	   On return results are passed via global variables as well:
+	   - ts_origin: originating greenlet (holds a reference)
+	   - ts_current: current greenlet (holds a reference)
+	   - ts_passaround_args: NULL if PyErr_Occurred(),
+	       else a tuple of args sent to ts_current (holds a reference)
+	   - ts_passaround_kwargs: switch kwargs (holds a reference)
+	   It is very important that stack switch is 'atomic', i.e. no
+	   calls into other Python code allowed (except very few that
+	   are safe), because global variables are very fragile.
+	*/
+	int err;
+	{   /* save state */
+		PyGreenlet* current = ts_current;
+		PyThreadState* tstate = PyThreadState_GET();
+		current->recursion_depth = tstate->recursion_depth;
+		current->top_frame = tstate->frame;
+#if GREENLET_USE_CONTEXT_VARS
+		current->context = tstate->context;
+#endif
+#ifdef GREENLET_USE_EXC_INFO
+		current->exc_info = tstate->exc_info;
+		current->exc_state = tstate->exc_state;
+#else
+		current->exc_type = tstate->exc_type;
+		current->exc_value = tstate->exc_value;
+		current->exc_traceback = tstate->exc_traceback;
+#endif
+	}
+	err = slp_switch();
+	if (err < 0) {   /* error */
+		PyGreenlet* current = ts_current;
+		current->top_frame = NULL;
+#ifdef GREENLET_USE_EXC_INFO
+		green_clear_exc(current);
+#else
+		current->exc_type = NULL;
+		current->exc_value = NULL;
+		current->exc_traceback = NULL;
+#endif
+
+		assert(ts_origin == NULL);
+		ts_target = NULL;
+	}
+	else {
+		PyGreenlet* target = ts_target;
+		PyGreenlet* origin = ts_current;
+		PyThreadState* tstate = PyThreadState_GET();
+		tstate->recursion_depth = target->recursion_depth;
+		tstate->frame = target->top_frame;
+		target->top_frame = NULL;
+
+#if GREENLET_USE_CONTEXT_VARS
+		tstate->context = target->context;
+		target->context = NULL;
+		/* Incrementing this value invalidates the contextvars cache,
+		   which would otherwise remain valid across switches */
+		tstate->context_ver++;
+#endif
+
+#ifdef GREENLET_USE_EXC_INFO
+		tstate->exc_state = target->exc_state;
+		tstate->exc_info = target->exc_info ? target->exc_info : &tstate->exc_state;
+#else
+		tstate->exc_type = target->exc_type;
+		tstate->exc_value = target->exc_value;
+		tstate->exc_traceback = target->exc_traceback;
+#endif
+		green_clear_exc(target);
+
+		assert(ts_origin == NULL);
+		Py_INCREF(target);
+		ts_current = target;
+		ts_origin = origin;
+		ts_target = NULL;
+	}
+	return err;
+}
+
+#if GREENLET_USE_TRACING
+static int
+g_calltrace(PyObject* tracefunc, PyObject* event, PyGreenlet* origin, PyGreenlet* target)
+{
+	PyObject *retval;
+	PyObject *exc_type, *exc_val, *exc_tb;
+	PyThreadState *tstate;
+	PyErr_Fetch(&exc_type, &exc_val, &exc_tb);
+	tstate = PyThreadState_GET();
+	tstate->tracing++;
+	tstate->use_tracing = 0;
+	retval = PyObject_CallFunction(tracefunc, "O(OO)", event, origin, target);
+	tstate->tracing--;
+	tstate->use_tracing = (tstate->tracing <= 0 &&
+	                       ((tstate->c_tracefunc != NULL) ||
+	                        (tstate->c_profilefunc != NULL)));
+	if (retval == NULL) {
+		/* In case of exceptions trace function is removed */
+		if (PyDict_GetItem(tstate->dict, ts_tracekey))
+			PyDict_DelItem(tstate->dict, ts_tracekey);
+		Py_XDECREF(exc_type);
+		Py_XDECREF(exc_val);
+		Py_XDECREF(exc_tb);
+		return -1;
+	} else
+		Py_DECREF(retval);
+	PyErr_Restore(exc_type, exc_val, exc_tb);
+	return 0;
+}
+#endif
+
+static PyObject *
+g_switch(PyGreenlet* target, PyObject* args, PyObject* kwargs)
+{
+	/* _consumes_ a reference to the args tuple and kwargs dict,
+	   and return a new tuple reference */
+	int err = 0;
+	PyObject* run_info;
+
+	/* check ts_current */
+	if (!STATE_OK) {
+		Py_XDECREF(args);
+		Py_XDECREF(kwargs);
+		return NULL;
+	}
+	run_info = green_statedict(target);
+	if (run_info == NULL || run_info != ts_current->run_info) {
+		Py_XDECREF(args);
+		Py_XDECREF(kwargs);
+		PyErr_SetString(PyExc_GreenletError, run_info
+		                ? "cannot switch to a different thread"
+		                : "cannot switch to a garbage collected greenlet");
+		return NULL;
+	}
+
+	ts_passaround_args = args;
+	ts_passaround_kwargs = kwargs;
+
+	/* find the real target by ignoring dead greenlets,
+	   and if necessary starting a greenlet. */
+	while (target) {
+		if (PyGreenlet_ACTIVE(target)) {
+			ts_target = target;
+			err = g_switchstack();
+			break;
+		}
+		if (!PyGreenlet_STARTED(target)) {
+			void* dummymarker;
+			ts_target = target;
+			err = g_initialstub(&dummymarker);
+			if (err == 1) {
+				continue; /* retry the switch */
+			}
+			break;
+		}
+		target = target->parent;
+	}
+
+	/* For a very short time, immediately after the 'atomic'
+	   g_switchstack() call, global variables are in a known state.
+	   We need to save everything we need, before it is destroyed
+	   by calls into arbitrary Python code. */
+	args = ts_passaround_args;
+	ts_passaround_args = NULL;
+	kwargs = ts_passaround_kwargs;
+	ts_passaround_kwargs = NULL;
+	if (err < 0) {
+		/* Turn switch errors into switch throws */
+		assert(ts_origin == NULL);
+		Py_CLEAR(kwargs);
+		Py_CLEAR(args);
+	} else {
+		PyGreenlet *origin;
+#if GREENLET_USE_TRACING
+		PyGreenlet *current;
+		PyObject *tracefunc;
+#endif
+		origin = ts_origin;
+		ts_origin = NULL;
+#if GREENLET_USE_TRACING
+		current = ts_current;
+		if ((tracefunc = PyDict_GetItem(current->run_info, ts_tracekey)) != NULL) {
+			Py_INCREF(tracefunc);
+			if (g_calltrace(tracefunc, args ? ts_event_switch : ts_event_throw, origin, current) < 0) {
+				/* Turn trace errors into switch throws */
+				Py_CLEAR(kwargs);
+				Py_CLEAR(args);
+			}
+			Py_DECREF(tracefunc);
+		}
+#endif
+		Py_DECREF(origin);
+	}
+
+	/* We need to figure out what values to pass to the target greenlet
+	   based on the arguments that have been passed to greenlet.switch(). If
+	   switch() was just passed an arg tuple, then we'll just return that.
+	   If only keyword arguments were passed, then we'll pass the keyword
+	   argument dict. Otherwise, we'll create a tuple of (args, kwargs) and
+	   return both. */
+	if (kwargs == NULL)
+	{
+		return args;
+	}
+	else if (PyDict_Size(kwargs) == 0)
+	{
+		Py_DECREF(kwargs);
+		return args;
+	}
+	else if (PySequence_Length(args) == 0)
+	{
+		Py_DECREF(args);
+		return kwargs;
+	}
+	else
+	{
+		PyObject *tuple = PyTuple_New(2);
+		if (tuple == NULL) {
+			Py_DECREF(args);
+			Py_DECREF(kwargs);
+			return NULL;
+		}
+		PyTuple_SET_ITEM(tuple, 0, args);
+		PyTuple_SET_ITEM(tuple, 1, kwargs);
+		return tuple;
+	}
+}
+
+static PyObject *
+g_handle_exit(PyObject *result)
+{
+	if (result == NULL && PyErr_ExceptionMatches(PyExc_GreenletExit))
+	{
+		/* catch and ignore GreenletExit */
+		PyObject *exc, *val, *tb;
+		PyErr_Fetch(&exc, &val, &tb);
+		if (val == NULL)
+		{
+			Py_INCREF(Py_None);
+			val = Py_None;
+		}
+		result = val;
+		Py_DECREF(exc);
+		Py_XDECREF(tb);
+	}
+	if (result != NULL)
+	{
+		/* package the result into a 1-tuple */
+		PyObject *r = result;
+		result = PyTuple_New(1);
+		if (result)
+		{
+			PyTuple_SET_ITEM(result, 0, r);
+		}
+		else
+		{
+			Py_DECREF(r);
+		}
+	}
+	return result;
+}
+
+static int GREENLET_NOINLINE(g_initialstub)(void* mark)
+{
+	int err;
+	PyObject *o, *run;
+	PyObject *exc, *val, *tb;
+	PyObject *run_info;
+	PyGreenlet* self = ts_target;
+	PyObject* args = ts_passaround_args;
+	PyObject* kwargs = ts_passaround_kwargs;
+
+	/* save exception in case getattr clears it */
+	PyErr_Fetch(&exc, &val, &tb);
+	/* self.run is the object to call in the new greenlet */
+	run = PyObject_GetAttrString((PyObject*) self, "run");
+	if (run == NULL) {
+		Py_XDECREF(exc);
+		Py_XDECREF(val);
+		Py_XDECREF(tb);
+		return -1;
+	}
+	/* restore saved exception */
+	PyErr_Restore(exc, val, tb);
+
+	/* recheck the state in case getattr caused thread switches */
+	if (!STATE_OK) {
+		Py_DECREF(run);
+		return -1;
+	}
+
+	/* recheck run_info in case greenlet reparented anywhere above */
+	run_info = green_statedict(self);
+	if (run_info == NULL || run_info != ts_current->run_info) {
+		Py_DECREF(run);
+		PyErr_SetString(PyExc_GreenletError, run_info
+		                ? "cannot switch to a different thread"
+		                : "cannot switch to a garbage collected greenlet");
+		return -1;
+	}
+
+	/* by the time we got here another start could happen elsewhere,
+	 * that means it should now be a regular switch
+	 */
+	if (PyGreenlet_STARTED(self)) {
+		Py_DECREF(run);
+		ts_passaround_args = args;
+		ts_passaround_kwargs = kwargs;
+		return 1;
+	}
+
+	/* start the greenlet */
+	self->stack_start = NULL;
+	self->stack_stop = (char*) mark;
+	if (ts_current->stack_start == NULL) {
+		/* ts_current is dying */
+		self->stack_prev = ts_current->stack_prev;
+	}
+	else {
+		self->stack_prev = ts_current;
+	}
+	self->top_frame = NULL;
+	green_clear_exc(self);
+	self->recursion_depth = PyThreadState_GET()->recursion_depth;
+
+	/* restore arguments in case they are clobbered */
+	ts_target = self;
+	ts_passaround_args = args;
+	ts_passaround_kwargs = kwargs;
+
+	/* perform the initial switch */
+	err = g_switchstack();
+
+	/* returns twice!
+	   The 1st time with err=1: we are in the new greenlet
+	   The 2nd time with err=0: back in the caller's greenlet
+	*/
+	if (err == 1) {
+		/* in the new greenlet */
+		PyGreenlet* origin;
+#if GREENLET_USE_TRACING
+		PyObject* tracefunc;
+#endif
+		PyObject* result;
+		PyGreenlet* parent;
+		self->stack_start = (char*) 1;  /* running */
+
+		/* grab origin while we still can */
+		origin = ts_origin;
+		ts_origin = NULL;
+
+		/* now use run_info to store the statedict */
+		o = self->run_info;
+		self->run_info = green_statedict(self->parent);
+		Py_INCREF(self->run_info);
+		Py_XDECREF(o);
+
+#if GREENLET_USE_TRACING
+		if ((tracefunc = PyDict_GetItem(self->run_info, ts_tracekey)) != NULL) {
+			Py_INCREF(tracefunc);
+			if (g_calltrace(tracefunc, args ? ts_event_switch : ts_event_throw, origin, self) < 0) {
+				/* Turn trace errors into switch throws */
+				Py_CLEAR(kwargs);
+				Py_CLEAR(args);
+			}
+			Py_DECREF(tracefunc);
+		}
+#endif
+		Py_DECREF(origin);
+
+		if (args == NULL) {
+			/* pending exception */
+			result = NULL;
+		} else {
+			/* call g.run(*args, **kwargs) */
+			result = PyObject_Call(run, args, kwargs);
+			Py_DECREF(args);
+			Py_XDECREF(kwargs);
+		}
+		Py_DECREF(run);
+		result = g_handle_exit(result);
+
+		/* jump back to parent */
+		self->stack_start = NULL;  /* dead */
+		for (parent = self->parent; parent != NULL; parent = parent->parent) {
+			result = g_switch(parent, result, NULL);
+			/* Return here means switch to parent failed,
+			 * in which case we throw *current* exception
+			 * to the next parent in chain.
+			 */
+			assert(result == NULL);
+		}
+		/* We ran out of parents, cannot continue */
+		PyErr_WriteUnraisable((PyObject *) self);
+		Py_FatalError("greenlets cannot continue");
+	}
+	/* back in the parent */
+	if (err < 0) {
+		/* start failed badly, restore greenlet state */
+		self->stack_start = NULL;
+		self->stack_stop = NULL;
+		self->stack_prev = NULL;
+	}
+	return err;
+}
+
+
+/***********************************************************/
+
+
+static PyObject* green_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+	PyObject* o = PyBaseObject_Type.tp_new(type, ts_empty_tuple, ts_empty_dict);
+	if (o != NULL) {
+		if (!STATE_OK) {
+			Py_DECREF(o);
+			return NULL;
+		}
+		Py_INCREF(ts_current);
+		((PyGreenlet*) o)->parent = ts_current;
+	}
+	return o;
+}
+
+static int green_setrun(PyGreenlet* self, PyObject* nrun, void* c);
+static int green_setparent(PyGreenlet* self, PyObject* nparent, void* c);
+
+static int green_init(PyGreenlet *self, PyObject *args, PyObject *kwargs)
+{
+	PyObject *run = NULL;
+	PyObject* nparent = NULL;
+	static char *kwlist[] = {"run", "parent", 0};
+	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|OO:green", kwlist,
+	                                 &run, &nparent))
+		return -1;
+
+	if (run != NULL) {
+		if (green_setrun(self, run, NULL))
+			return -1;
+	}
+	if (nparent != NULL && nparent != Py_None)
+		return green_setparent(self, nparent, NULL);
+	return 0;
+}
+
+static int kill_greenlet(PyGreenlet* self)
+{
+	/* Cannot raise an exception to kill the greenlet if
+	   it is not running in the same thread! */
+	if (self->run_info == PyThreadState_GET()->dict) {
+		/* The dying greenlet cannot be a parent of ts_current
+		   because the 'parent' field chain would hold a
+		   reference */
+		PyObject* result;
+		PyGreenlet* oldparent;
+		PyGreenlet* tmp;
+		if (!STATE_OK) {
+			return -1;
+		}
+		oldparent = self->parent;
+		self->parent = ts_current;
+		Py_INCREF(self->parent);
+		/* Send the greenlet a GreenletExit exception. */
+		PyErr_SetNone(PyExc_GreenletExit);
+		result = g_switch(self, NULL, NULL);
+		tmp = self->parent;
+		self->parent = oldparent;
+		Py_XDECREF(tmp);
+		if (result == NULL)
+			return -1;
+		Py_DECREF(result);
+		return 0;
+	}
+	else {
+		/* Not the same thread! Temporarily save the greenlet
+		   into its thread's ts_delkey list. */
+		PyObject* lst;
+		lst = PyDict_GetItem(self->run_info, ts_delkey);
+		if (lst == NULL) {
+			lst = PyList_New(0);
+			if (lst == NULL || PyDict_SetItem(self->run_info,
+			                                  ts_delkey, lst) < 0)
+				return -1;
+		}
+		if (PyList_Append(lst, (PyObject*) self) < 0)
+			return -1;
+		if (!STATE_OK)  /* to force ts_delkey to be reconsidered */
+			return -1;
+		return 0;
+	}
+}
+
+#if GREENLET_USE_GC
+static int
+green_traverse(PyGreenlet *self, visitproc visit, void *arg)
+{
+	/* We must only visit referenced objects, i.e. only objects
+	   Py_INCREF'ed by this greenlet (directly or indirectly):
+	   - stack_prev is not visited: holds previous stack pointer, but it's not referenced
+	   - frames are not visited: alive greenlets are not garbage collected anyway */
+	Py_VISIT((PyObject*)self->parent);
+	Py_VISIT(self->run_info);
+#if GREENLET_USE_CONTEXT_VARS
+	Py_VISIT(self->context);
+#endif
+#ifdef GREENLET_USE_EXC_INFO
+	Py_VISIT(self->exc_state.exc_type);
+	Py_VISIT(self->exc_state.exc_value);
+	Py_VISIT(self->exc_state.exc_traceback);
+#else
+	Py_VISIT(self->exc_type);
+	Py_VISIT(self->exc_value);
+	Py_VISIT(self->exc_traceback);
+#endif
+	Py_VISIT(self->dict);
+	return 0;
+}
+
+static int green_is_gc(PyGreenlet* self)
+{
+	/* Main greenlet can be garbage collected since it can only
+	   become unreachable if the underlying thread exited.
+	   Active greenlet cannot be garbage collected, however. */
+	if (PyGreenlet_MAIN(self) || !PyGreenlet_ACTIVE(self))
+		return 1;
+	return 0;
+}
+
+static int green_clear(PyGreenlet* self)
+{
+	/* Greenlet is only cleared if it is about to be collected.
+	   Since active greenlets are not garbage collectable, we can
+	   be sure that, even if they are deallocated during clear,
+	   nothing they reference is in unreachable or finalizers,
+	   so even if it switches we are relatively safe. */
+	Py_CLEAR(self->parent);
+	Py_CLEAR(self->run_info);
+#if GREENLET_USE_CONTEXT_VARS
+	Py_CLEAR(self->context);
+#endif
+#ifdef GREENLET_USE_EXC_INFO
+	Py_CLEAR(self->exc_state.exc_type);
+	Py_CLEAR(self->exc_state.exc_value);
+	Py_CLEAR(self->exc_state.exc_traceback);
+#else
+	Py_CLEAR(self->exc_type);
+	Py_CLEAR(self->exc_value);
+	Py_CLEAR(self->exc_traceback);
+#endif
+	Py_CLEAR(self->dict);
+	return 0;
+}
+#endif
+
+static void green_dealloc(PyGreenlet* self)
+{
+	PyObject *error_type, *error_value, *error_traceback;
+	Py_ssize_t refcnt;
+
+#if GREENLET_USE_GC
+	PyObject_GC_UnTrack(self);
+#endif
+
+	if (PyGreenlet_ACTIVE(self) && self->run_info != NULL && !PyGreenlet_MAIN(self)) {
+		/* Hacks hacks hacks copied from instance_dealloc() */
+		/* Temporarily resurrect the greenlet. */
+		assert(Py_REFCNT(self) == 0);
+		Py_SET_REFCNT(self, 1);
+		/* Save the current exception, if any. */
+		PyErr_Fetch(&error_type, &error_value, &error_traceback);
+		if (kill_greenlet(self) < 0) {
+			PyErr_WriteUnraisable((PyObject*) self);
+			/* XXX what else should we do? */
+		}
+		/* Check for no resurrection must be done while we keep
+		 * our internal reference, otherwise PyFile_WriteObject
+		 * causes recursion if using Py_INCREF/Py_DECREF
+		 */
+		if (Py_REFCNT(self) == 1 && PyGreenlet_ACTIVE(self)) {
+			/* Not resurrected, but still not dead!
+			   XXX what else should we do? we complain. */
+			PyObject* f = PySys_GetObject("stderr");
+			Py_INCREF(self); /* leak! */
+			if (f != NULL) {
+				PyFile_WriteString("GreenletExit did not kill ",
+				                   f);
+				PyFile_WriteObject((PyObject*) self, f, 0);
+				PyFile_WriteString("\n", f);
+			}
+		}
+		/* Restore the saved exception. */
+		PyErr_Restore(error_type, error_value, error_traceback);
+		/* Undo the temporary resurrection; can't use DECREF here,
+		 * it would cause a recursive call.
+		 */
+		assert(Py_REFCNT(self) > 0);
+
+		refcnt = Py_REFCNT(self) - 1;
+		Py_SET_REFCNT(self, refcnt);
+		if (refcnt != 0) {
+			/* Resurrected! */
+			_Py_NewReference((PyObject*) self);
+			Py_SET_REFCNT(self, refcnt);
+#if GREENLET_USE_GC
+			PyObject_GC_Track((PyObject *)self);
+#endif
+			_Py_DEC_REFTOTAL;
+#ifdef COUNT_ALLOCS
+			--Py_TYPE(self)->tp_frees;
+			--Py_TYPE(self)->tp_allocs;
+#endif /* COUNT_ALLOCS */
+			return;
+		}
+	}
+	if (self->weakreflist != NULL)
+		PyObject_ClearWeakRefs((PyObject *) self);
+	Py_CLEAR(self->parent);
+	Py_CLEAR(self->run_info);
+#if GREENLET_USE_CONTEXT_VARS
+	Py_CLEAR(self->context);
+#endif
+#ifdef GREENLET_USE_EXC_INFO
+	Py_CLEAR(self->exc_state.exc_type);
+	Py_CLEAR(self->exc_state.exc_value);
+	Py_CLEAR(self->exc_state.exc_traceback);
+#else
+	Py_CLEAR(self->exc_type);
+	Py_CLEAR(self->exc_value);
+	Py_CLEAR(self->exc_traceback);
+#endif
+	Py_CLEAR(self->dict);
+	Py_TYPE(self)->tp_free((PyObject*) self);
+}
+
+static PyObject* single_result(PyObject* results)
+{
+	if (results != NULL && PyTuple_Check(results) &&
+	    PyTuple_GET_SIZE(results) == 1) {
+		PyObject *result = PyTuple_GET_ITEM(results, 0);
+		Py_INCREF(result);
+		Py_DECREF(results);
+		return result;
+	}
+	else
+		return results;
+}
+
+static PyObject *
+throw_greenlet(PyGreenlet *self, PyObject *typ, PyObject *val, PyObject *tb)
+{
+	/* Note: _consumes_ a reference to typ, val, tb */
+	PyObject *result = NULL;
+	PyErr_Restore(typ, val, tb);
+	if (PyGreenlet_STARTED(self) && !PyGreenlet_ACTIVE(self))
+	{
+		/* dead greenlet: turn GreenletExit into a regular return */
+		result = g_handle_exit(result);
+	}
+	return single_result(g_switch(self, result, NULL));
+}
+
+PyDoc_STRVAR(green_switch_doc,
+"switch(*args, **kwargs)\n"
+"\n"
+"Switch execution to this greenlet.\n"
+"\n"
+"If this greenlet has never been run, then this greenlet\n"
+"will be switched to using the body of self.run(*args, **kwargs).\n"
+"\n"
+"If the greenlet is active (has been run, but was switch()'ed\n"
+"out before leaving its run function), then this greenlet will\n"
+"be resumed and the return value to its switch call will be\n"
+"None if no arguments are given, the given argument if one\n"
+"argument is given, or the args tuple and keyword args dict if\n"
+"multiple arguments are given.\n"
+"\n"
+"If the greenlet is dead, or is the current greenlet then this\n"
+"function will simply return the arguments using the same rules as\n"
+"above.\n");
+
+static PyObject* green_switch(
+	PyGreenlet* self,
+	PyObject* args,
+	PyObject* kwargs)
+{
+	Py_INCREF(args);
+	Py_XINCREF(kwargs);
+	return single_result(g_switch(self, args, kwargs));
+}
+
+PyDoc_STRVAR(green_throw_doc,
+"Switches execution to the greenlet ``g``, but immediately raises the\n"
+"given exception in ``g``.  If no argument is provided, the exception\n"
+"defaults to ``greenlet.GreenletExit``.  The normal exception\n"
+"propagation rules apply, as described above.  Note that calling this\n"
+"method is almost equivalent to the following::\n"
+"\n"
+"    def raiser():\n"
+"        raise typ, val, tb\n"
+"    g_raiser = greenlet(raiser, parent=g)\n"
+"    g_raiser.switch()\n"
+"\n"
+"except that this trick does not work for the\n"
+"``greenlet.GreenletExit`` exception, which would not propagate\n"
+"from ``g_raiser`` to ``g``.\n");
+
+static PyObject *
+green_throw(PyGreenlet *self, PyObject *args)
+{
+	PyObject *typ = PyExc_GreenletExit;
+	PyObject *val = NULL;
+	PyObject *tb = NULL;
+
+	if (!PyArg_ParseTuple(args, "|OOO:throw", &typ, &val, &tb))
+	{
+		return NULL;
+	}
+
+	/* First, check the traceback argument, replacing None, with NULL */
+	if (tb == Py_None)
+	{
+		tb = NULL;
+	}
+	else if (tb != NULL && !PyTraceBack_Check(tb))
+	{
+		PyErr_SetString(
+			PyExc_TypeError,
+			"throw() third argument must be a traceback object");
+		return NULL;
+	}
+
+	Py_INCREF(typ);
+	Py_XINCREF(val);
+	Py_XINCREF(tb);
+
+	if (PyExceptionClass_Check(typ))
+	{
+		PyErr_NormalizeException(&typ, &val, &tb);
+	}
+	else if (PyExceptionInstance_Check(typ))
+	{
+		/* Raising an instance. The value should be a dummy. */
+		if (val && val != Py_None)
+		{
+			PyErr_SetString(
+				PyExc_TypeError,
+				"instance exception may not have a separate value");
+			goto failed_throw;
+		}
+		else
+		{
+			/* Normalize to raise <class>, <instance> */
+			Py_XDECREF(val);
+			val = typ;
+			typ = PyExceptionInstance_Class(typ);
+			Py_INCREF(typ);
+		}
+	}
+	else
+	{
+		/* Not something you can raise. throw() fails. */
+		PyErr_Format(
+			PyExc_TypeError,
+			"exceptions must be classes, or instances, not %s",
+			Py_TYPE(typ)->tp_name);
+		goto failed_throw;
+	}
+
+	return throw_greenlet(self, typ, val, tb);
+
+failed_throw:
+	/* Didn't use our arguments, so restore their original refcounts */
+	Py_DECREF(typ);
+	Py_XDECREF(val);
+	Py_XDECREF(tb);
+	return NULL;
+}
+
+static int green_bool(PyGreenlet* self)
+{
+	return PyGreenlet_ACTIVE(self);
+}
+
+static PyObject* green_getdict(PyGreenlet* self, void* c)
+{
+	if (self->dict == NULL) {
+		self->dict = PyDict_New();
+		if (self->dict == NULL)
+			return NULL;
+	}
+	Py_INCREF(self->dict);
+	return self->dict;
+}
+
+static int green_setdict(PyGreenlet* self, PyObject* val, void* c)
+{
+	PyObject* tmp;
+
+	if (val == NULL) {
+		PyErr_SetString(PyExc_TypeError, "__dict__ may not be deleted");
+		return -1;
+	}
+	if (!PyDict_Check(val)) {
+		PyErr_SetString(PyExc_TypeError, "__dict__ must be a dictionary");
+		return -1;
+	}
+	tmp = self->dict;
+	Py_INCREF(val);
+	self->dict = val;
+	Py_XDECREF(tmp);
+	return 0;
+}
+
+static PyObject* green_getdead(PyGreenlet* self, void* c)
+{
+	if (PyGreenlet_ACTIVE(self) || !PyGreenlet_STARTED(self))
+		Py_RETURN_FALSE;
+	else
+		Py_RETURN_TRUE;
+}
+
+
+static PyObject* green_get_stack_saved(PyGreenlet* self, void* c)
+{
+	return PyLong_FromSsize_t(self->stack_saved);
+}
+
+
+static PyObject* green_getrun(PyGreenlet* self, void* c)
+{
+	if (PyGreenlet_STARTED(self) || self->run_info == NULL) {
+		PyErr_SetString(PyExc_AttributeError, "run");
+		return NULL;
+	}
+	Py_INCREF(self->run_info);
+	return self->run_info;
+}
+
+static int green_setrun(PyGreenlet* self, PyObject* nrun, void* c)
+{
+	PyObject* o;
+	if (PyGreenlet_STARTED(self)) {
+		PyErr_SetString(PyExc_AttributeError,
+		                "run cannot be set "
+		                "after the start of the greenlet");
+		return -1;
+	}
+	o = self->run_info;
+	self->run_info = nrun;
+	Py_XINCREF(nrun);
+	Py_XDECREF(o);
+	return 0;
+}
+
+static PyObject* green_getparent(PyGreenlet* self, void* c)
+{
+	PyObject* result = self->parent ? (PyObject*) self->parent : Py_None;
+	Py_INCREF(result);
+	return result;
+}
+
+static int green_setparent(PyGreenlet* self, PyObject* nparent, void* c)
+{
+	PyGreenlet* p;
+	PyObject* run_info = NULL;
+	if (nparent == NULL) {
+		PyErr_SetString(PyExc_AttributeError, "can't delete attribute");
+		return -1;
+	}
+	if (!PyGreenlet_Check(nparent)) {
+		PyErr_SetString(PyExc_TypeError, "parent must be a greenlet");
+		return -1;
+	}
+	for (p=(PyGreenlet*) nparent; p; p=p->parent) {
+		if (p == self) {
+			PyErr_SetString(PyExc_ValueError, "cyclic parent chain");
+			return -1;
+		}
+		run_info = PyGreenlet_ACTIVE(p) ? p->run_info : NULL;
+	}
+	if (run_info == NULL) {
+		PyErr_SetString(PyExc_ValueError, "parent must not be garbage collected");
+		return -1;
+	}
+	if (PyGreenlet_STARTED(self) && self->run_info != run_info) {
+		PyErr_SetString(PyExc_ValueError, "parent cannot be on a different thread");
+		return -1;
+	}
+	p = self->parent;
+	self->parent = (PyGreenlet*) nparent;
+	Py_INCREF(nparent);
+	Py_XDECREF(p);
+	return 0;
+}
+
+#ifdef Py_CONTEXT_H
+#define GREENLET_NO_CONTEXTVARS_REASON "This build of greenlet"
+#else
+#define GREENLET_NO_CONTEXTVARS_REASON "This Python interpreter"
+#endif
+
+static PyObject* green_getcontext(PyGreenlet* self, void* c)
+{
+#if GREENLET_USE_CONTEXT_VARS
+	PyThreadState* tstate = PyThreadState_GET();
+	PyObject* result;
+
+	if (!STATE_OK) {
+		return NULL;
+	}
+	if (PyGreenlet_ACTIVE(self) && self->top_frame == NULL) {
+		/* Currently running greenlet: context is stored in the thread state,
+		   not the greenlet object. */
+		if (self == ts_current) {
+			result = tstate->context;
+		}
+		else {
+			PyErr_SetString(PyExc_ValueError,
+					"cannot get context of a "
+					"greenlet that is running in a different thread");
+			return NULL;
+		}
+	}
+	else {
+		/* Greenlet is not running: just return context. */
+		result = self->context;
+	}
+	if (result == NULL) {
+		result = Py_None;
+	}
+	Py_INCREF(result);
+	return result;
+#else
+	PyErr_SetString(PyExc_AttributeError,
+			GREENLET_NO_CONTEXTVARS_REASON
+			" does not support context variables");
+	return NULL;
+#endif
+}
+
+static int green_setcontext(PyGreenlet* self, PyObject* nctx, void* c)
+{
+#if GREENLET_USE_CONTEXT_VARS
+	PyThreadState* tstate;
+	PyObject* octx = NULL;
+	if (!STATE_OK) {
+		return -1;
+	}
+	if (nctx == NULL) {
+		PyErr_SetString(PyExc_AttributeError, "can't delete attribute");
+		return -1;
+	}
+	if (nctx == Py_None) {
+		/* "Empty context" is stored as NULL, not None. */
+		nctx = NULL;
+	}
+	else if (!PyContext_CheckExact(nctx)) {
+		PyErr_SetString(PyExc_TypeError,
+				"greenlet context must be a "
+				"contextvars.Context or None");
+		return -1;
+	}
+	tstate = PyThreadState_GET();
+	if (PyGreenlet_ACTIVE(self) && self->top_frame == NULL) {
+		/* Currently running greenlet: context is stored in the thread state,
+		   not the greenlet object. */
+		if (self == ts_current) {
+			octx = tstate->context;
+			tstate->context = nctx;
+			tstate->context_ver++;
+			Py_XINCREF(nctx);
+		}
+		else {
+			PyErr_SetString(PyExc_ValueError,
+					"cannot set context of a "
+					"greenlet that is running in a different thread");
+			return -1;
+		}
+	}
+	else {
+		/* Greenlet is not running: just set context. */
+		octx = self->context;
+		self->context = nctx;
+		Py_XINCREF(nctx);
+	}
+	Py_XDECREF(octx);
+	return 0;
+#else
+	PyErr_SetString(PyExc_AttributeError,
+			GREENLET_NO_CONTEXTVARS_REASON
+			" does not support context variables");
+	return -1;
+#endif
+}
+
+#undef GREENLET_NO_CONTEXTVARS_REASON
+
+static PyObject* green_getframe(PyGreenlet* self, void* c)
+{
+	PyObject* result = self->top_frame ? (PyObject*) self->top_frame : Py_None;
+	Py_INCREF(result);
+	return result;
+}
+
+static PyObject* green_getstate(PyGreenlet* self)
+{
+	PyErr_Format(PyExc_TypeError,
+	             "cannot serialize '%s' object",
+	             Py_TYPE(self)->tp_name);
+	return NULL;
+}
+
+
+/*****************************************************************************
+ * C interface
+ *
+ * These are exported using the CObject API
+ */
+
+static PyGreenlet *
+PyGreenlet_GetCurrent(void)
+{
+	if (!STATE_OK) {
+		return NULL;
+	}
+	Py_INCREF(ts_current);
+	return ts_current;
+}
+
+static int
+PyGreenlet_SetParent(PyGreenlet *g, PyGreenlet *nparent)
+{
+	if (!PyGreenlet_Check(g)) {
+		PyErr_SetString(PyExc_TypeError, "parent must be a greenlet");
+		return -1;
+	}
+
+	return green_setparent((PyGreenlet*) g, (PyObject *) nparent, NULL);
+}
+
+static PyGreenlet *
+PyGreenlet_New(PyObject *run, PyGreenlet *parent)
+{
+	PyGreenlet* g = NULL;
+
+	g = (PyGreenlet *) PyType_GenericAlloc(&PyGreenlet_Type, 0);
+	if (g == NULL) {
+		return NULL;
+	}
+
+	if (run != NULL) {
+		Py_INCREF(run);
+		g->run_info = run;
+	}
+
+	if (parent != NULL) {
+		if (PyGreenlet_SetParent(g, parent)) {
+			Py_DECREF(g);
+			return NULL;
+		}
+	} else {
+		if ((g->parent = PyGreenlet_GetCurrent()) == NULL) {
+			Py_DECREF(g);
+			return NULL;
+		}
+	}
+
+	return g;
+}
+
+static PyObject *
+PyGreenlet_Switch(PyGreenlet *g, PyObject *args, PyObject *kwargs)
+{
+	PyGreenlet *self = (PyGreenlet *) g;
+
+	if (!PyGreenlet_Check(self)) {
+		PyErr_BadArgument();
+		return NULL;
+	}
+
+	if (args == NULL) {
+		args = Py_BuildValue("()");
+	}
+	else {
+		Py_INCREF(args);
+	}
+
+	if (kwargs != NULL && PyDict_Check(kwargs)) {
+		Py_INCREF(kwargs);
+	}
+	else {
+		kwargs = NULL;
+	}
+
+	return single_result(g_switch(self, args, kwargs));
+}
+
+static PyObject *
+PyGreenlet_Throw(PyGreenlet *self, PyObject *typ, PyObject *val, PyObject *tb)
+{
+	if (!PyGreenlet_Check(self)) {
+		PyErr_BadArgument();
+		return NULL;
+	}
+	Py_INCREF(typ);
+	Py_XINCREF(val);
+	Py_XINCREF(tb);
+	return throw_greenlet(self, typ, val, tb);
+}
+
+/** End C API ****************************************************************/
+
+static PyMethodDef green_methods[] = {
+	{"switch", (PyCFunction)green_switch,
+	 METH_VARARGS | METH_KEYWORDS, green_switch_doc},
+	{"throw",  (PyCFunction)green_throw,  METH_VARARGS, green_throw_doc},
+	{"__getstate__", (PyCFunction)green_getstate, METH_NOARGS, NULL},
+	{NULL,     NULL} /* sentinel */
+};
+
+static PyGetSetDef green_getsets[] = {
+	{"__dict__", (getter)green_getdict,
+	             (setter)green_setdict, /*XXX*/ NULL},
+	{"run",      (getter)green_getrun,
+	             (setter)green_setrun, /*XXX*/ NULL},
+	{"parent",   (getter)green_getparent,
+	             (setter)green_setparent, /*XXX*/ NULL},
+	{"gr_frame", (getter)green_getframe,
+	             NULL, /*XXX*/ NULL},
+	{"gr_context", (getter)green_getcontext,
+	             (setter)green_setcontext, /*XXX*/ NULL},
+	{"dead",     (getter)green_getdead,
+	             NULL, /*XXX*/ NULL},
+	{"_stack_saved", (getter)green_get_stack_saved,
+	             NULL, /*XXX*/ NULL},
+	{NULL}
+};
+
+static PyNumberMethods green_as_number = {
+	NULL,                /* nb_add */
+	NULL,                /* nb_subtract */
+	NULL,                /* nb_multiply */
+#if PY_MAJOR_VERSION < 3
+	NULL,                /* nb_divide */
+#endif
+	NULL,                /* nb_remainder */
+	NULL,                /* nb_divmod */
+	NULL,                /* nb_power */
+	NULL,                /* nb_negative */
+	NULL,                /* nb_positive */
+	NULL,                /* nb_absolute */
+	(inquiry)green_bool, /* nb_bool */
+};
+
+
+PyTypeObject PyGreenlet_Type = {
+	PyVarObject_HEAD_INIT(NULL, 0)
+	"greenlet.greenlet",                    /* tp_name */
+	sizeof(PyGreenlet),                     /* tp_basicsize */
+	0,                                      /* tp_itemsize */
+	/* methods */
+	(destructor)green_dealloc,              /* tp_dealloc */
+	0,                                      /* tp_print */
+	0,                                      /* tp_getattr */
+	0,                                      /* tp_setattr */
+	0,                                      /* tp_compare */
+	0,                                      /* tp_repr */
+	&green_as_number,                       /* tp_as _number*/
+	0,                                      /* tp_as _sequence*/
+	0,                                      /* tp_as _mapping*/
+	0,                                      /* tp_hash */
+	0,                                      /* tp_call */
+	0,                                      /* tp_str */
+	0,                                      /* tp_getattro */
+	0,                                      /* tp_setattro */
+	0,                                      /* tp_as_buffer*/
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | GREENLET_GC_FLAGS, /* tp_flags */
+	"greenlet(run=None, parent=None) -> greenlet\n\n"
+	"Creates a new greenlet object (without running it).\n\n"
+	" - *run* -- The callable to invoke.\n"
+	" - *parent* -- The parent greenlet. The default is the current "
+	"greenlet.",                            /* tp_doc */
+	(traverseproc)GREENLET_tp_traverse,     /* tp_traverse */
+	(inquiry)GREENLET_tp_clear,             /* tp_clear */
+	0,                                      /* tp_richcompare */
+	offsetof(PyGreenlet, weakreflist),      /* tp_weaklistoffset */
+	0,                                      /* tp_iter */
+	0,                                      /* tp_iternext */
+	green_methods,                          /* tp_methods */
+	0,                                      /* tp_members */
+	green_getsets,                          /* tp_getset */
+	0,                                      /* tp_base */
+	0,                                      /* tp_dict */
+	0,                                      /* tp_descr_get */
+	0,                                      /* tp_descr_set */
+	offsetof(PyGreenlet, dict),             /* tp_dictoffset */
+	(initproc)green_init,                   /* tp_init */
+	GREENLET_tp_alloc,                      /* tp_alloc */
+	green_new,                              /* tp_new */
+	GREENLET_tp_free,                       /* tp_free */
+	(inquiry)GREENLET_tp_is_gc,             /* tp_is_gc */
+};
+
+static PyObject* mod_getcurrent(PyObject* self)
+{
+	if (!STATE_OK)
+		return NULL;
+	Py_INCREF(ts_current);
+	return (PyObject*) ts_current;
+}
+
+#if GREENLET_USE_TRACING
+static PyObject* mod_settrace(PyObject* self, PyObject* args)
+{
+	int err;
+	PyObject* previous;
+	PyObject* tracefunc;
+	PyGreenlet* current;
+	if (!PyArg_ParseTuple(args, "O", &tracefunc))
+		return NULL;
+	if (!STATE_OK)
+		return NULL;
+	current = ts_current;
+	previous = PyDict_GetItem(current->run_info, ts_tracekey);
+	if (previous == NULL)
+		previous = Py_None;
+	Py_INCREF(previous);
+	if (tracefunc == Py_None)
+		err = previous != Py_None ? PyDict_DelItem(current->run_info, ts_tracekey) : 0;
+	else
+		err = PyDict_SetItem(current->run_info, ts_tracekey, tracefunc);
+	if (err < 0)
+		Py_CLEAR(previous);
+	return previous;
+}
+
+static PyObject* mod_gettrace(PyObject* self)
+{
+	PyObject* tracefunc;
+	if (!STATE_OK)
+		return NULL;
+	tracefunc = PyDict_GetItem(ts_current->run_info, ts_tracekey);
+	if (tracefunc == NULL)
+		tracefunc = Py_None;
+	Py_INCREF(tracefunc);
+	return tracefunc;
+}
+#endif
+
+static PyMethodDef GreenMethods[] = {
+	{"getcurrent", (PyCFunction)mod_getcurrent, METH_NOARGS, /*XXX*/ NULL},
+#if GREENLET_USE_TRACING
+	{"settrace", (PyCFunction)mod_settrace, METH_VARARGS, NULL},
+	{"gettrace", (PyCFunction)mod_gettrace, METH_NOARGS, NULL},
+#endif
+	{NULL,     NULL}        /* Sentinel */
+};
+
+static char* copy_on_greentype[] = {
+	"getcurrent",
+	"error",
+	"GreenletExit",
+#if GREENLET_USE_TRACING
+	"settrace",
+	"gettrace",
+#endif
+	NULL
+};
+
+#if PY_MAJOR_VERSION >= 3
+#define INITERROR return NULL
+
+static struct PyModuleDef greenlet_module_def = {
+	PyModuleDef_HEAD_INIT,
+	"greenlet._greenlet",
+	NULL,
+	-1,
+	GreenMethods,
+};
+
+PyMODINIT_FUNC
+PyInit__greenlet(void)
+#else
+#define INITERROR return
+
+PyMODINIT_FUNC
+init_greenlet(void)
+#endif
+{
+	PyObject* m = NULL;
+	char** p = NULL;
+	PyObject *c_api_object;
+	static void *_PyGreenlet_API[PyGreenlet_API_pointers];
+
+	GREENLET_NOINLINE_INIT();
+
+#if PY_MAJOR_VERSION >= 3
+	m = PyModule_Create(&greenlet_module_def);
+#else
+	m = Py_InitModule("greenlet._greenlet", GreenMethods);
+#endif
+	if (m == NULL)
+	{
+		INITERROR;
+	}
+
+	if (PyModule_AddStringConstant(m, "__version__", GREENLET_VERSION) < 0)
+	{
+		INITERROR;
+	}
+
+#if PY_MAJOR_VERSION >= 3
+	ts_curkey = PyUnicode_InternFromString("__greenlet_ts_curkey");
+	ts_delkey = PyUnicode_InternFromString("__greenlet_ts_delkey");
+#if GREENLET_USE_TRACING
+	ts_tracekey = PyUnicode_InternFromString("__greenlet_ts_tracekey");
+	ts_event_switch = PyUnicode_InternFromString("switch");
+	ts_event_throw = PyUnicode_InternFromString("throw");
+#endif
+#else
+	ts_curkey = PyString_InternFromString("__greenlet_ts_curkey");
+	ts_delkey = PyString_InternFromString("__greenlet_ts_delkey");
+#if GREENLET_USE_TRACING
+	ts_tracekey = PyString_InternFromString("__greenlet_ts_tracekey");
+	ts_event_switch = PyString_InternFromString("switch");
+	ts_event_throw = PyString_InternFromString("throw");
+#endif
+#endif
+	if (ts_curkey == NULL || ts_delkey == NULL)
+	{
+		INITERROR;
+	}
+	if (PyType_Ready(&PyGreenlet_Type) < 0)
+	{
+		INITERROR;
+	}
+	PyExc_GreenletError = PyErr_NewException("greenlet.error", NULL, NULL);
+	if (PyExc_GreenletError == NULL)
+	{
+		INITERROR;
+	}
+	PyExc_GreenletExit = PyErr_NewException("greenlet.GreenletExit",
+	                                        PyExc_BaseException, NULL);
+	if (PyExc_GreenletExit == NULL)
+	{
+		INITERROR;
+	}
+
+	ts_empty_tuple = PyTuple_New(0);
+	if (ts_empty_tuple == NULL)
+	{
+		INITERROR;
+	}
+
+	ts_empty_dict = PyDict_New();
+	if (ts_empty_dict == NULL)
+	{
+		INITERROR;
+	}
+
+	ts_current = green_create_main();
+	if (ts_current == NULL)
+	{
+		INITERROR;
+	}
+
+	Py_INCREF(&PyGreenlet_Type);
+	PyModule_AddObject(m, "greenlet", (PyObject*) &PyGreenlet_Type);
+	Py_INCREF(PyExc_GreenletError);
+	PyModule_AddObject(m, "error", PyExc_GreenletError);
+	Py_INCREF(PyExc_GreenletExit);
+	PyModule_AddObject(m, "GreenletExit", PyExc_GreenletExit);
+	PyModule_AddObject(m, "GREENLET_USE_GC", PyBool_FromLong(GREENLET_USE_GC));
+	PyModule_AddObject(m, "GREENLET_USE_TRACING", PyBool_FromLong(GREENLET_USE_TRACING));
+	PyModule_AddObject(m, "GREENLET_USE_CONTEXT_VARS", PyBool_FromLong(GREENLET_USE_CONTEXT_VARS));
+
+	/* also publish module-level data as attributes of the greentype. */
+	for (p=copy_on_greentype; *p; p++) {
+		PyObject* o = PyObject_GetAttrString(m, *p);
+		if (!o) continue;
+		PyDict_SetItemString(PyGreenlet_Type.tp_dict, *p, o);
+		Py_DECREF(o);
+	}
+
+	/*
+	 * Expose C API
+	 */
+
+	/* types */
+	_PyGreenlet_API[PyGreenlet_Type_NUM] = (void *) &PyGreenlet_Type;
+
+	/* exceptions */
+	_PyGreenlet_API[PyExc_GreenletError_NUM] = (void *) PyExc_GreenletError;
+	_PyGreenlet_API[PyExc_GreenletExit_NUM] = (void *) PyExc_GreenletExit;
+
+	/* methods */
+	_PyGreenlet_API[PyGreenlet_New_NUM] = (void *) PyGreenlet_New;
+	_PyGreenlet_API[PyGreenlet_GetCurrent_NUM] =
+		(void *) PyGreenlet_GetCurrent;
+	_PyGreenlet_API[PyGreenlet_Throw_NUM] = (void *) PyGreenlet_Throw;
+	_PyGreenlet_API[PyGreenlet_Switch_NUM] = (void *) PyGreenlet_Switch;
+	_PyGreenlet_API[PyGreenlet_SetParent_NUM] =
+		(void *) PyGreenlet_SetParent;
+
+	/* XXX: Note that our module name is ``greenlet._greenlet``, but for
+	   backwards compatibility with existing C code, we need the _C_API to
+	   be directly in greenlet.
+	*/
+	c_api_object = PyCapsule_New((void *) _PyGreenlet_API, "greenlet._C_API", NULL);
+	if (c_api_object != NULL)
+	{
+		PyModule_AddObject(m, "_C_API", c_api_object);
+	}
+
+#if PY_MAJOR_VERSION >= 3
+	return m;
+#endif
+}
diff --git a/src/greenlet/greenlet.h b/src/greenlet/greenlet.h
new file mode 100644
index 0000000..68fc035
--- /dev/null
+++ b/src/greenlet/greenlet.h
@@ -0,0 +1,150 @@
+/* vim:set noet ts=8 sw=8 : */
+
+/* Greenlet object interface */
+
+#ifndef Py_GREENLETOBJECT_H
+#define Py_GREENLETOBJECT_H
+
+#include <Python.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define GREENLET_VERSION "1.0.0.dev0"
+
+#if PY_VERSION_HEX >= 0x030700A3
+#  define GREENLET_USE_EXC_INFO
+#endif
+
+#ifndef GREENLET_USE_CONTEXT_VARS
+#ifdef Py_CONTEXT_H
+#define GREENLET_USE_CONTEXT_VARS 1
+#else
+#define GREENLET_USE_CONTEXT_VARS 0
+#endif
+#endif
+
+typedef struct _greenlet {
+	PyObject_HEAD
+	char* stack_start;
+	char* stack_stop;
+	char* stack_copy;
+	intptr_t stack_saved;
+	struct _greenlet* stack_prev;
+	struct _greenlet* parent;
+	PyObject* run_info;
+	struct _frame* top_frame;
+	int recursion_depth;
+	PyObject* weakreflist;
+#ifdef GREENLET_USE_EXC_INFO
+	_PyErr_StackItem* exc_info;
+	_PyErr_StackItem exc_state;
+#else
+	PyObject* exc_type;
+	PyObject* exc_value;
+	PyObject* exc_traceback;
+#endif
+	PyObject* dict;
+#if GREENLET_USE_CONTEXT_VARS
+	PyObject* context;
+#endif
+} PyGreenlet;
+
+#define PyGreenlet_Check(op)      PyObject_TypeCheck(op, &PyGreenlet_Type)
+#define PyGreenlet_MAIN(op)       (((PyGreenlet*)(op))->stack_stop == (char*) -1)
+#define PyGreenlet_STARTED(op)    (((PyGreenlet*)(op))->stack_stop != NULL)
+#define PyGreenlet_ACTIVE(op)     (((PyGreenlet*)(op))->stack_start != NULL)
+#define PyGreenlet_GET_PARENT(op) (((PyGreenlet*)(op))->parent)
+
+/* C API functions */
+
+/* Total number of symbols that are exported */
+#define PyGreenlet_API_pointers  8
+
+#define PyGreenlet_Type_NUM       0
+#define PyExc_GreenletError_NUM   1
+#define PyExc_GreenletExit_NUM    2
+
+#define PyGreenlet_New_NUM        3
+#define PyGreenlet_GetCurrent_NUM 4
+#define PyGreenlet_Throw_NUM      5
+#define PyGreenlet_Switch_NUM     6
+#define PyGreenlet_SetParent_NUM  7
+
+#ifndef GREENLET_MODULE
+/* This section is used by modules that uses the greenlet C API */
+static void **_PyGreenlet_API = NULL;
+
+#define PyGreenlet_Type (*(PyTypeObject *) _PyGreenlet_API[PyGreenlet_Type_NUM])
+
+#define PyExc_GreenletError \
+	((PyObject *) _PyGreenlet_API[PyExc_GreenletError_NUM])
+
+#define PyExc_GreenletExit \
+	((PyObject *) _PyGreenlet_API[PyExc_GreenletExit_NUM])
+
+/*
+ * PyGreenlet_New(PyObject *args)
+ *
+ * greenlet.greenlet(run, parent=None)
+ */
+#define PyGreenlet_New \
+	(* (PyGreenlet * (*)(PyObject *run, PyGreenlet *parent)) \
+	 _PyGreenlet_API[PyGreenlet_New_NUM])
+
+/*
+ * PyGreenlet_GetCurrent(void)
+ *
+ * greenlet.getcurrent()
+ */
+#define PyGreenlet_GetCurrent \
+	(* (PyGreenlet * (*)(void)) _PyGreenlet_API[PyGreenlet_GetCurrent_NUM])
+
+/*
+ * PyGreenlet_Throw(
+ *         PyGreenlet *greenlet,
+ *         PyObject *typ,
+ *         PyObject *val,
+ *         PyObject *tb)
+ *
+ * g.throw(...)
+ */
+#define PyGreenlet_Throw \
+	(* (PyObject * (*) \
+	    (PyGreenlet *self, PyObject *typ, PyObject *val, PyObject *tb)) \
+	 _PyGreenlet_API[PyGreenlet_Throw_NUM])
+
+/*
+ * PyGreenlet_Switch(PyGreenlet *greenlet, PyObject *args)
+ *
+ * g.switch(*args, **kwargs)
+ */
+#define PyGreenlet_Switch \
+	(* (PyObject * (*)(PyGreenlet *greenlet, PyObject *args, PyObject *kwargs)) \
+	 _PyGreenlet_API[PyGreenlet_Switch_NUM])
+
+/*
+ * PyGreenlet_SetParent(PyObject *greenlet, PyObject *new_parent)
+ *
+ * g.parent = new_parent
+ */
+#define PyGreenlet_SetParent \
+	(* (int (*)(PyGreenlet *greenlet, PyGreenlet *nparent)) \
+	 _PyGreenlet_API[PyGreenlet_SetParent_NUM])
+
+/* Macro that imports greenlet and initializes C API */
+/* NOTE: This has actually moved to ``greenlet._greenlet._C_API``, but we
+   keep the older definition to be sure older code that might have a copy of
+   the header still works. */
+#define PyGreenlet_Import() \
+{ \
+	_PyGreenlet_API = (void**)PyCapsule_Import("greenlet._C_API", 0); \
+}
+
+#endif /* GREENLET_MODULE */
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* !Py_GREENLETOBJECT_H */
diff --git a/src/greenlet/platform/setup_switch_x64_masm.cmd b/src/greenlet/platform/setup_switch_x64_masm.cmd
new file mode 100644
index 0000000..0928595
--- /dev/null
+++ b/src/greenlet/platform/setup_switch_x64_masm.cmd
@@ -0,0 +1,2 @@
+call "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\vcvarsall.bat" amd64

+ml64 /nologo /c /Fo switch_x64_masm.obj switch_x64_masm.asm

diff --git a/src/greenlet/platform/switch_aarch64_gcc.h b/src/greenlet/platform/switch_aarch64_gcc.h
new file mode 100644
index 0000000..0b9d556
--- /dev/null
+++ b/src/greenlet/platform/switch_aarch64_gcc.h
@@ -0,0 +1,69 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 07-Sep-16 Add clang support using x register naming. Fredrik Fornwall
+ * 13-Apr-13 Add support for strange GCC caller-save decisions
+ * 08-Apr-13 File creation. Michael Matz
+ *
+ * NOTES
+ *
+ * Simply save all callee saved registers
+ *
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+#define STACK_MAGIC 0
+#define REGS_TO_SAVE "x19", "x20", "x21", "x22", "x23", "x24", "x25", "x26", \
+                     "x27", "x28", "x30" /* aka lr */, \
+                     "v8", "v9", "v10", "v11", \
+                     "v12", "v13", "v14", "v15"
+
+static int
+slp_switch(void)
+{
+	int err;
+	void *fp;
+        register long *stackref, stsizediff;
+        __asm__ volatile ("" : : : REGS_TO_SAVE);
+	__asm__ volatile ("str x29, %0" : "=m"(fp) : : );
+        __asm__ ("mov %0, sp" : "=r" (stackref));
+        {
+                SLP_SAVE_STATE(stackref, stsizediff);
+                __asm__ volatile (
+                    "add sp,sp,%0\n"
+                    "add x29,x29,%0\n"
+                    :
+                    : "r" (stsizediff)
+                    );
+		SLP_RESTORE_STATE();
+		/* SLP_SAVE_STATE macro contains some return statements
+		   (of -1 and 1).  It falls through only when
+		   the return value of slp_save_state() is zero, which
+		   is placed in x0.
+		   In that case we (slp_switch) also want to return zero
+		   (also in x0 of course).
+		   Now, some GCC versions (seen with 4.8) think it's a
+		   good idea to save/restore x0 around the call to
+		   slp_restore_state(), instead of simply zeroing it
+		   at the return below.  But slp_restore_state
+		   writes random values to the stack slot used for this
+		   save/restore (from when it once was saved above in
+		   SLP_SAVE_STATE, when it was still uninitialized), so
+		   "restoring" that precious zero actually makes us
+		   return random values.  There are some ways to make
+		   GCC not use that zero value in the normal return path
+		   (e.g. making err volatile, but that costs a little
+		   stack space), and the simplest is to call a function
+		   that returns an unknown value (which happens to be zero),
+		   so the saved/restored value is unused.  */
+           __asm__ volatile ("mov %0, #0" : "=r" (err));
+        }
+        __asm__ volatile ("ldr x29, %0" : : "m" (fp) :);
+        __asm__ volatile ("" : : : REGS_TO_SAVE);
+        return err;
+}
+
+#endif
diff --git a/src/greenlet/platform/switch_alpha_unix.h b/src/greenlet/platform/switch_alpha_unix.h
new file mode 100644
index 0000000..216619f
--- /dev/null
+++ b/src/greenlet/platform/switch_alpha_unix.h
@@ -0,0 +1,30 @@
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+#define STACK_MAGIC 0
+
+#define REGS_TO_SAVE "$9", "$10", "$11", "$12", "$13", "$14", "$15", \
+		     "$f2", "$f3", "$f4", "$f5", "$f6", "$f7", "$f8", "$f9"
+
+static int
+slp_switch(void)
+{
+  register int ret;
+  register long *stackref, stsizediff;
+  __asm__ volatile ("" : : : REGS_TO_SAVE);
+  __asm__ volatile ("mov $30, %0" : "=r" (stackref) : );
+  {
+      SLP_SAVE_STATE(stackref, stsizediff);
+      __asm__ volatile (
+	  "addq $30, %0, $30\n\t"
+	  : /* no outputs */
+	  : "r" (stsizediff)
+	  );
+      SLP_RESTORE_STATE();
+  }
+  __asm__ volatile ("" : : : REGS_TO_SAVE);
+  __asm__ volatile ("mov $31, %0" : "=r" (ret) : );
+  return ret;
+}
+
+#endif
diff --git a/src/greenlet/platform/switch_amd64_unix.h b/src/greenlet/platform/switch_amd64_unix.h
new file mode 100644
index 0000000..16b99b7
--- /dev/null
+++ b/src/greenlet/platform/switch_amd64_unix.h
@@ -0,0 +1,84 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 3-May-13   Ralf Schmitt  <ralf@systemexit.de>
+ *     Add support for strange GCC caller-save decisions
+ *     (ported from switch_aarch64_gcc.h)
+ * 18-Aug-11  Alexey Borzenkov  <snaury@gmail.com>
+ *      Correctly save rbp, csr and cw
+ * 01-Apr-04  Hye-Shik Chang    <perky@FreeBSD.org>
+ *      Ported from i386 to amd64.
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      slightly changed framework for spark
+ * 31-Avr-02  Armin Rigo         <arigo@ulb.ac.be>
+ *      Added ebx, esi and edi register-saves.
+ * 01-Mar-02  Samual M. Rushing  <rushing@ironport.com>
+ *      Ported from i386.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+/* #define STACK_MAGIC 3 */
+/* the above works fine with gcc 2.96, but 2.95.3 wants this */
+#define STACK_MAGIC 0
+
+#define REGS_TO_SAVE "r12", "r13", "r14", "r15"
+
+static int
+slp_switch(void)
+{
+    int err;
+    void* rbp;
+    void* rbx;
+    unsigned int csr;
+    unsigned short cw;
+    register long *stackref, stsizediff;
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("fstcw %0" : "=m" (cw));
+    __asm__ volatile ("stmxcsr %0" : "=m" (csr));
+    __asm__ volatile ("movq %%rbp, %0" : "=m" (rbp));
+    __asm__ volatile ("movq %%rbx, %0" : "=m" (rbx));
+    __asm__ ("movq %%rsp, %0" : "=g" (stackref));
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ volatile (
+            "addq %0, %%rsp\n"
+            "addq %0, %%rbp\n"
+            :
+            : "r" (stsizediff)
+            );
+        SLP_RESTORE_STATE();
+        __asm__ volatile ("xorq %%rax, %%rax" : "=a" (err));
+    }
+    __asm__ volatile ("movq %0, %%rbx" : : "m" (rbx));
+    __asm__ volatile ("movq %0, %%rbp" : : "m" (rbp));
+    __asm__ volatile ("ldmxcsr %0" : : "m" (csr));
+    __asm__ volatile ("fldcw %0" : : "m" (cw));
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    return err;
+}
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/* 
+ * if you want to add self-inspection tools, place them
+ * here. See the x86_msvc for the necessary defines.
+ * These features are highly experimental und not
+ * essential yet.
+ */
diff --git a/src/greenlet/platform/switch_arm32_gcc.h b/src/greenlet/platform/switch_arm32_gcc.h
new file mode 100644
index 0000000..035d6b9
--- /dev/null
+++ b/src/greenlet/platform/switch_arm32_gcc.h
@@ -0,0 +1,79 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 14-Aug-06 File creation. Ported from Arm Thumb. Sylvain Baro
+ *  3-Sep-06 Commented out saving of r1-r3 (r4 already commented out) as I
+ *           read that these do not need to be saved.  Also added notes and
+ *           errors related to the frame pointer. Richard Tew.
+ *
+ * NOTES
+ *
+ *   It is not possible to detect if fp is used or not, so the supplied
+ *   switch function needs to support it, so that you can remove it if
+ *   it does not apply to you.
+ *
+ * POSSIBLE ERRORS
+ *
+ *   "fp cannot be used in asm here"
+ *
+ *   - Try commenting out "fp" in REGS_TO_SAVE.
+ *
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+#define STACK_MAGIC 0
+#define REG_SP "sp"
+#define REG_SPSP "sp,sp"
+#ifdef __thumb__
+#define REG_FP "r7"
+#define REG_FPFP "r7,r7"
+#define REGS_TO_SAVE_GENERAL "r4", "r5", "r6", "r8", "r9", "r10", "r11", "lr"
+#else
+#define REG_FP "fp"
+#define REG_FPFP "fp,fp"
+#define REGS_TO_SAVE_GENERAL "r4", "r5", "r6", "r7", "r8", "r9", "r10", "lr"
+#endif
+#if defined(__SOFTFP__)
+#define REGS_TO_SAVE REGS_TO_SAVE_GENERAL
+#elif defined(__VFP_FP__)
+#define REGS_TO_SAVE REGS_TO_SAVE_GENERAL, "d8", "d9", "d10", "d11", \
+                                           "d12", "d13", "d14", "d15"
+#elif defined(__MAVERICK__)
+#define REGS_TO_SAVE REGS_TO_SAVE_GENERAL, "mvf4", "mvf5", "mvf6", "mvf7", \
+                                           "mvf8", "mvf9", "mvf10", "mvf11", \
+                                           "mvf12", "mvf13", "mvf14", "mvf15"
+#else
+#define REGS_TO_SAVE REGS_TO_SAVE_GENERAL, "f4", "f5", "f6", "f7"
+#endif
+
+static int
+#ifdef __GNUC__
+__attribute__((optimize("no-omit-frame-pointer")))
+#endif
+slp_switch(void)
+{
+        void *fp;
+        register int *stackref, stsizediff;
+        int result;
+        __asm__ volatile ("" : : : REGS_TO_SAVE);
+        __asm__ volatile ("mov r0," REG_FP "\n\tstr r0,%0" : "=m" (fp) : : "r0");
+        __asm__ ("mov %0," REG_SP : "=r" (stackref));
+        {
+                SLP_SAVE_STATE(stackref, stsizediff);
+                __asm__ volatile (
+                    "add " REG_SPSP ",%0\n"
+                    "add " REG_FPFP ",%0\n"
+                    :
+                    : "r" (stsizediff)
+                    );
+                SLP_RESTORE_STATE();
+        }
+        __asm__ volatile ("ldr r0,%1\n\tmov " REG_FP ",r0\n\tmov %0, #0" : "=r" (result) : "m" (fp) : "r0");
+        __asm__ volatile ("" : : : REGS_TO_SAVE);
+        return result;
+}
+
+#endif
diff --git a/src/greenlet/platform/switch_arm32_ios.h b/src/greenlet/platform/switch_arm32_ios.h
new file mode 100644
index 0000000..e993707
--- /dev/null
+++ b/src/greenlet/platform/switch_arm32_ios.h
@@ -0,0 +1,67 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 31-May-15 iOS support. Ported from arm32. Proton <feisuzhu@163.com>
+ *
+ * NOTES
+ *
+ *   It is not possible to detect if fp is used or not, so the supplied
+ *   switch function needs to support it, so that you can remove it if
+ *   it does not apply to you.
+ *
+ * POSSIBLE ERRORS
+ *
+ *   "fp cannot be used in asm here"
+ *
+ *   - Try commenting out "fp" in REGS_TO_SAVE.
+ *
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#define STACK_MAGIC 0
+#define REG_SP "sp"
+#define REG_SPSP "sp,sp"
+#define REG_FP "r7"
+#define REG_FPFP "r7,r7"
+#define REGS_TO_SAVE_GENERAL "r4", "r5", "r6", "r8", "r10", "r11", "lr"
+#define REGS_TO_SAVE REGS_TO_SAVE_GENERAL, "d8", "d9", "d10", "d11", \
+                                           "d12", "d13", "d14", "d15"
+
+static int
+#ifdef __GNUC__
+__attribute__((optimize("no-omit-frame-pointer")))
+#endif
+slp_switch(void)
+{
+        void *fp;
+        register int *stackref, stsizediff, result;
+        __asm__ volatile ("" : : : REGS_TO_SAVE);
+        __asm__ volatile ("str " REG_FP ",%0" : "=m" (fp));
+        __asm__ ("mov %0," REG_SP : "=r" (stackref));
+        {
+                SLP_SAVE_STATE(stackref, stsizediff);
+                __asm__ volatile (
+                    "add " REG_SPSP ",%0\n"
+                    "add " REG_FPFP ",%0\n"
+                    :
+                    : "r" (stsizediff)
+                    : REGS_TO_SAVE /* Clobber registers, force compiler to
+                                    * recalculate address of void *fp from REG_SP or REG_FP */
+                );
+                SLP_RESTORE_STATE();
+        }
+        __asm__ volatile (
+            "ldr " REG_FP ", %1\n\t"
+            "mov %0, #0"
+            : "=r" (result)
+            : "m" (fp)
+            : REGS_TO_SAVE /* Force compiler to restore saved registers after this */
+        );
+        return result;
+}
+
+#endif
diff --git a/src/greenlet/platform/switch_csky_gcc.h b/src/greenlet/platform/switch_csky_gcc.h
new file mode 100644
index 0000000..7486b94
--- /dev/null
+++ b/src/greenlet/platform/switch_csky_gcc.h
@@ -0,0 +1,48 @@
+#ifdef SLP_EVAL
+#define STACK_MAGIC 0
+#define REG_FP "r8"
+#ifdef __CSKYABIV2__
+#define REGS_TO_SAVE_GENERAL "r4", "r5", "r6", "r7", "r9", "r10", "r11", "r15",\
+                             "r16", "r17", "r18", "r19", "r20", "r21", "r22",\
+                             "r23", "r24", "r25"
+
+#if defined (__CSKY_HARD_FLOAT__) || (__CSKY_VDSP__)
+#define REGS_TO_SAVE REGS_TO_SAVE_GENERAL, "vr8", "vr9", "vr10", "vr11", "vr12",\
+                                           "vr13", "vr14", "vr15"
+#else
+#define REGS_TO_SAVE REGS_TO_SAVE_GENERAL
+#endif
+#else
+#define REGS_TO_SAVE "r9", "r10", "r11", "r12", "r13", "r15"
+#endif
+
+
+static int
+#ifdef __GNUC__
+__attribute__((optimize("no-omit-frame-pointer")))
+#endif
+slp_switch(void)
+{
+        register int *stackref, stsizediff;
+        int result;
+
+        __asm__ volatile ("" : : : REGS_TO_SAVE);
+        __asm__ ("mov %0, sp" : "=r" (stackref));
+        {
+                SLP_SAVE_STATE(stackref, stsizediff);
+                __asm__ volatile (
+                    "addu sp,%0\n"
+                    "addu "REG_FP",%0\n"
+                    :
+                    : "r" (stsizediff)
+                    );
+		
+                SLP_RESTORE_STATE();
+        }
+        __asm__ volatile ("movi %0, 0" : "=r" (result));
+        __asm__ volatile ("" : : : REGS_TO_SAVE);
+
+        return result;
+}
+
+#endif
diff --git a/src/greenlet/platform/switch_m68k_gcc.h b/src/greenlet/platform/switch_m68k_gcc.h
new file mode 100644
index 0000000..da761c2
--- /dev/null
+++ b/src/greenlet/platform/switch_m68k_gcc.h
@@ -0,0 +1,38 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 2014-01-06  Andreas Schwab  <schwab@linux-m68k.org>
+ *      File created.
+ */
+
+#ifdef SLP_EVAL
+
+#define STACK_MAGIC 0
+
+#define REGS_TO_SAVE "%d2", "%d3", "%d4", "%d5", "%d6", "%d7", \
+		     "%a2", "%a3", "%a4"
+
+static int
+slp_switch(void)
+{
+  int err;
+  int *stackref, stsizediff;
+  void *fp, *a5;
+  __asm__ volatile ("" : : : REGS_TO_SAVE);
+  __asm__ volatile ("move.l %%fp, %0" : "=m"(fp));
+  __asm__ volatile ("move.l %%a5, %0" : "=m"(a5));
+  __asm__ ("move.l %%sp, %0" : "=r"(stackref));
+  {
+    SLP_SAVE_STATE(stackref, stsizediff);
+    __asm__ volatile ("add.l %0, %%sp; add.l %0, %%fp" : : "r"(stsizediff));
+    SLP_RESTORE_STATE();
+    __asm__ volatile ("clr.l %0" : "=g" (err));
+  }
+  __asm__ volatile ("move.l %0, %%a5" : : "m"(a5));
+  __asm__ volatile ("move.l %0, %%fp" : : "m"(fp));
+  __asm__ volatile ("" : : : REGS_TO_SAVE);
+  return err;
+}
+
+#endif
diff --git a/src/greenlet/platform/switch_mips_unix.h b/src/greenlet/platform/switch_mips_unix.h
new file mode 100644
index 0000000..1916b26
--- /dev/null
+++ b/src/greenlet/platform/switch_mips_unix.h
@@ -0,0 +1,64 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 20-Sep-14 Matt Madison <madison@bliss-m.org>
+ *      Re-code the saving of the gp register for MIPS64.
+ * 05-Jan-08 Thiemo Seufer  <ths@debian.org>
+ *      Ported from ppc.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#define STACK_MAGIC 0
+
+#define REGS_TO_SAVE "$16", "$17", "$18", "$19", "$20", "$21", "$22", \
+       "$23", "$30"
+static int
+slp_switch(void)
+{
+    register int err;
+    register int *stackref, stsizediff;
+#ifdef __mips64
+    uint64_t gpsave;
+#endif
+    __asm__ __volatile__ ("" : : : REGS_TO_SAVE);
+#ifdef __mips64
+    __asm__ __volatile__ ("sd $28,%0" : "=m" (gpsave) : : );
+#endif
+    __asm__ ("move %0, $29" : "=r" (stackref) : );
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ __volatile__ (
+#ifdef __mips64
+            "daddu $29, %0\n"
+#else
+            "addu $29, %0\n"
+#endif
+            : /* no outputs */
+            : "r" (stsizediff)
+            );
+        SLP_RESTORE_STATE();
+    }
+#ifdef __mips64
+    __asm__ __volatile__ ("ld $28,%0" : : "m" (gpsave) : );
+#endif
+    __asm__ __volatile__ ("" : : : REGS_TO_SAVE);
+    __asm__ __volatile__ ("move %0, $0" : "=r" (err));
+    return err;
+}
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/*
+ * if you want to add self-inspection tools, place them
+ * here. See the x86_msvc for the necessary defines.
+ * These features are highly experimental und not
+ * essential yet.
+ */
diff --git a/src/greenlet/platform/switch_ppc64_aix.h b/src/greenlet/platform/switch_ppc64_aix.h
new file mode 100644
index 0000000..e07b8de
--- /dev/null
+++ b/src/greenlet/platform/switch_ppc64_aix.h
@@ -0,0 +1,103 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 16-Oct-20  Jesse Gorzinski <jgorzins@us.ibm.com>
+ *      Copied from Linux PPC64 implementation
+ * 04-Sep-18  Alexey Borzenkov  <snaury@gmail.com>
+ *      Workaround a gcc bug using manual save/restore of r30
+ * 21-Mar-18  Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>
+ *      Added r30 to the list of saved registers in order to fully comply with
+ *      both ppc64 ELFv1 ABI and the ppc64le ELFv2 ABI, that classify this
+ *      register as a nonvolatile register used for local variables.
+ * 21-Mar-18  Laszlo Boszormenyi  <gcs@debian.org>
+ *      Save r2 (TOC pointer) manually.
+ * 10-Dec-13  Ulrich Weigand  <uweigand@de.ibm.com>
+ *	Support ELFv2 ABI.  Save float/vector registers.
+ * 09-Mar-12 Michael Ellerman <michael@ellerman.id.au>
+ *      64-bit implementation, copied from 32-bit.
+ * 07-Sep-05 (py-dev mailing list discussion)
+ *      removed 'r31' from the register-saved.  !!!! WARNING !!!!
+ *      It means that this file can no longer be compiled statically!
+ *      It is now only suitable as part of a dynamic library!
+ * 14-Jan-04  Bob Ippolito <bob@redivi.com>
+ *      added cr2-cr4 to the registers to be saved.
+ *      Open questions: Should we save FP registers?
+ *      What about vector registers?
+ *      Differences between darwin and unix?
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 04-Oct-02  Gustavo Niemeyer <niemeyer@conectiva.com>
+ *      Ported from MacOS version.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      slightly changed framework for sparc
+ * 29-Jun-02  Christian Tismer  <tismer@tismer.com>
+ *      Added register 13-29, 31 saves. The same way as
+ *      Armin Rigo did for the x86_unix version.
+ *      This seems to be now fully functional!
+ * 04-Mar-02  Hye-Shik Chang  <perky@fallin.lv>
+ *      Ported from i386.
+ * 31-Jul-12  Trevor Bowen    <trevorbowen@gmail.com>
+ *      Changed memory constraints to register only.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#define STACK_MAGIC 6
+
+#if defined(__ALTIVEC__)
+#define ALTIVEC_REGS \
+       "v20", "v21", "v22", "v23", "v24", "v25", "v26", "v27", \
+       "v28", "v29", "v30", "v31",
+#else
+#define ALTIVEC_REGS
+#endif
+
+#define REGS_TO_SAVE "r14", "r15", "r16", "r17", "r18", "r19", "r20",  \
+       "r21", "r22", "r23", "r24", "r25", "r26", "r27", "r28", "r29",  \
+       "r31",                                                    \
+       "fr14", "fr15", "fr16", "fr17", "fr18", "fr19", "fr20", "fr21", \
+       "fr22", "fr23", "fr24", "fr25", "fr26", "fr27", "fr28", "fr29", \
+       "fr30", "fr31", \
+       ALTIVEC_REGS \
+       "cr2", "cr3", "cr4"
+
+static int
+slp_switch(void)
+{
+    register int err;
+    register long *stackref, stsizediff;
+    void * toc;
+    void * r30;
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("std 2, %0" : "=m" (toc));
+    __asm__ volatile ("std 30, %0" : "=m" (r30));
+    __asm__ ("mr %0, 1" : "=r" (stackref) : );
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ volatile (
+            "mr 11, %0\n"
+            "add 1, 1, 11\n"
+            : /* no outputs */
+            : "r" (stsizediff)
+            : "11"
+            );
+        SLP_RESTORE_STATE();
+    }
+    __asm__ volatile ("ld 30, %0" : : "m" (r30));
+    __asm__ volatile ("ld 2, %0" : : "m" (toc));
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("li %0, 0" : "=r" (err));
+    return err;
+}
+
+#endif
diff --git a/src/greenlet/platform/switch_ppc64_linux.h b/src/greenlet/platform/switch_ppc64_linux.h
new file mode 100644
index 0000000..88e6847
--- /dev/null
+++ b/src/greenlet/platform/switch_ppc64_linux.h
@@ -0,0 +1,105 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 04-Sep-18  Alexey Borzenkov  <snaury@gmail.com>
+ *      Workaround a gcc bug using manual save/restore of r30
+ * 21-Mar-18  Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>
+ *      Added r30 to the list of saved registers in order to fully comply with
+ *      both ppc64 ELFv1 ABI and the ppc64le ELFv2 ABI, that classify this
+ *      register as a nonvolatile register used for local variables.
+ * 21-Mar-18  Laszlo Boszormenyi  <gcs@debian.org>
+ *      Save r2 (TOC pointer) manually.
+ * 10-Dec-13  Ulrich Weigand  <uweigand@de.ibm.com>
+ *	Support ELFv2 ABI.  Save float/vector registers.
+ * 09-Mar-12 Michael Ellerman <michael@ellerman.id.au>
+ *      64-bit implementation, copied from 32-bit.
+ * 07-Sep-05 (py-dev mailing list discussion)
+ *      removed 'r31' from the register-saved.  !!!! WARNING !!!!
+ *      It means that this file can no longer be compiled statically!
+ *      It is now only suitable as part of a dynamic library!
+ * 14-Jan-04  Bob Ippolito <bob@redivi.com>
+ *      added cr2-cr4 to the registers to be saved.
+ *      Open questions: Should we save FP registers?
+ *      What about vector registers?
+ *      Differences between darwin and unix?
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 04-Oct-02  Gustavo Niemeyer <niemeyer@conectiva.com>
+ *      Ported from MacOS version.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      slightly changed framework for sparc
+ * 29-Jun-02  Christian Tismer  <tismer@tismer.com>
+ *      Added register 13-29, 31 saves. The same way as
+ *      Armin Rigo did for the x86_unix version.
+ *      This seems to be now fully functional!
+ * 04-Mar-02  Hye-Shik Chang  <perky@fallin.lv>
+ *      Ported from i386.
+ * 31-Jul-12  Trevor Bowen    <trevorbowen@gmail.com>
+ *      Changed memory constraints to register only.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#if _CALL_ELF == 2
+#define STACK_MAGIC 4
+#else
+#define STACK_MAGIC 6
+#endif
+
+#if defined(__ALTIVEC__)
+#define ALTIVEC_REGS \
+       "v20", "v21", "v22", "v23", "v24", "v25", "v26", "v27", \
+       "v28", "v29", "v30", "v31",
+#else
+#define ALTIVEC_REGS
+#endif
+
+#define REGS_TO_SAVE "r14", "r15", "r16", "r17", "r18", "r19", "r20",  \
+       "r21", "r22", "r23", "r24", "r25", "r26", "r27", "r28", "r29",  \
+       "r31",                                                    \
+       "fr14", "fr15", "fr16", "fr17", "fr18", "fr19", "fr20", "fr21", \
+       "fr22", "fr23", "fr24", "fr25", "fr26", "fr27", "fr28", "fr29", \
+       "fr30", "fr31", \
+       ALTIVEC_REGS \
+       "cr2", "cr3", "cr4"
+
+static int
+slp_switch(void)
+{
+    register int err;
+    register long *stackref, stsizediff;
+    void * toc;
+    void * r30;
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("std 2, %0" : "=m" (toc));
+    __asm__ volatile ("std 30, %0" : "=m" (r30));
+    __asm__ ("mr %0, 1" : "=r" (stackref) : );
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ volatile (
+            "mr 11, %0\n"
+            "add 1, 1, 11\n"
+            : /* no outputs */
+            : "r" (stsizediff)
+            : "11"
+            );
+        SLP_RESTORE_STATE();
+    }
+    __asm__ volatile ("ld 30, %0" : : "m" (r30));
+    __asm__ volatile ("ld 2, %0" : : "m" (toc));
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("li %0, 0" : "=r" (err));
+    return err;
+}
+
+#endif
diff --git a/src/greenlet/platform/switch_ppc_aix.h b/src/greenlet/platform/switch_ppc_aix.h
new file mode 100644
index 0000000..c7d476f
--- /dev/null
+++ b/src/greenlet/platform/switch_ppc_aix.h
@@ -0,0 +1,87 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 07-Mar-11 Floris Bruynooghe <flub@devork.be>
+ *      Do not add stsizediff to general purpose
+ *      register (GPR) 30 as this is a non-volatile and
+ *      unused by the PowerOpen Environment, therefore
+ *      this was modifying a user register instead of the
+ *      frame pointer (which does not seem to exist).
+ * 07-Sep-05 (py-dev mailing list discussion)
+ *      removed 'r31' from the register-saved.  !!!! WARNING !!!!
+ *      It means that this file can no longer be compiled statically!
+ *      It is now only suitable as part of a dynamic library!
+ * 14-Jan-04  Bob Ippolito <bob@redivi.com>
+ *      added cr2-cr4 to the registers to be saved.
+ *      Open questions: Should we save FP registers?
+ *      What about vector registers?
+ *      Differences between darwin and unix?
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 04-Oct-02  Gustavo Niemeyer <niemeyer@conectiva.com>
+ *      Ported from MacOS version.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      slightly changed framework for sparc
+ * 29-Jun-02  Christian Tismer  <tismer@tismer.com>
+ *      Added register 13-29, 31 saves. The same way as
+ *      Armin Rigo did for the x86_unix version.
+ *      This seems to be now fully functional!
+ * 04-Mar-02  Hye-Shik Chang  <perky@fallin.lv>
+ *      Ported from i386.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#define STACK_MAGIC 3
+
+/* !!!!WARNING!!!! need to add "r31" in the next line if this header file
+ * is meant to be compiled non-dynamically!
+ */
+#define REGS_TO_SAVE "r13", "r14", "r15", "r16", "r17", "r18", "r19", "r20", \
+       "r21", "r22", "r23", "r24", "r25", "r26", "r27", "r28", "r29", \
+       "cr2", "cr3", "cr4"
+static int
+slp_switch(void)
+{
+    register int err;
+    register int *stackref, stsizediff;
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ ("mr %0, 1" : "=r" (stackref) : );
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ volatile (
+            "mr 11, %0\n"
+            "add 1, 1, 11\n"
+            : /* no outputs */
+            : "r" (stsizediff)
+            : "11"
+            );
+        SLP_RESTORE_STATE();
+    }
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("li %0, 0" : "=r" (err));
+    return err;
+}
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/*
+ * if you want to add self-inspection tools, place them
+ * here. See the x86_msvc for the necessary defines.
+ * These features are highly experimental und not
+ * essential yet.
+ */
diff --git a/src/greenlet/platform/switch_ppc_linux.h b/src/greenlet/platform/switch_ppc_linux.h
new file mode 100644
index 0000000..0a71255
--- /dev/null
+++ b/src/greenlet/platform/switch_ppc_linux.h
@@ -0,0 +1,84 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 07-Sep-05 (py-dev mailing list discussion)
+ *      removed 'r31' from the register-saved.  !!!! WARNING !!!!
+ *      It means that this file can no longer be compiled statically!
+ *      It is now only suitable as part of a dynamic library!
+ * 14-Jan-04  Bob Ippolito <bob@redivi.com>
+ *      added cr2-cr4 to the registers to be saved.
+ *      Open questions: Should we save FP registers?
+ *      What about vector registers?
+ *      Differences between darwin and unix?
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 04-Oct-02  Gustavo Niemeyer <niemeyer@conectiva.com>
+ *      Ported from MacOS version.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      slightly changed framework for sparc
+ * 29-Jun-02  Christian Tismer  <tismer@tismer.com>
+ *      Added register 13-29, 31 saves. The same way as
+ *      Armin Rigo did for the x86_unix version.
+ *      This seems to be now fully functional!
+ * 04-Mar-02  Hye-Shik Chang  <perky@fallin.lv>
+ *      Ported from i386.
+ * 31-Jul-12  Trevor Bowen    <trevorbowen@gmail.com>
+ *      Changed memory constraints to register only.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#define STACK_MAGIC 3
+
+/* !!!!WARNING!!!! need to add "r31" in the next line if this header file
+ * is meant to be compiled non-dynamically!
+ */
+#define REGS_TO_SAVE "r13", "r14", "r15", "r16", "r17", "r18", "r19", "r20", \
+       "r21", "r22", "r23", "r24", "r25", "r26", "r27", "r28", "r29", \
+       "cr2", "cr3", "cr4"
+static int
+slp_switch(void)
+{
+    register int err;
+    register int *stackref, stsizediff;
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ ("mr %0, 1" : "=r" (stackref) : );
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ volatile (
+            "mr 11, %0\n"
+            "add 1, 1, 11\n"
+            "add 30, 30, 11\n"
+            : /* no outputs */
+            : "r" (stsizediff)
+            : "11"
+            );
+        SLP_RESTORE_STATE();
+    }
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("li %0, 0" : "=r" (err));
+    return err;
+}
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/*
+ * if you want to add self-inspection tools, place them
+ * here. See the x86_msvc for the necessary defines.
+ * These features are highly experimental und not
+ * essential yet.
+ */
diff --git a/src/greenlet/platform/switch_ppc_macosx.h b/src/greenlet/platform/switch_ppc_macosx.h
new file mode 100644
index 0000000..56e573f
--- /dev/null
+++ b/src/greenlet/platform/switch_ppc_macosx.h
@@ -0,0 +1,82 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 07-Sep-05 (py-dev mailing list discussion)
+ *      removed 'r31' from the register-saved.  !!!! WARNING !!!!
+ *      It means that this file can no longer be compiled statically!
+ *      It is now only suitable as part of a dynamic library!
+ * 14-Jan-04  Bob Ippolito <bob@redivi.com>
+ *      added cr2-cr4 to the registers to be saved.
+ *      Open questions: Should we save FP registers?
+ *      What about vector registers?
+ *      Differences between darwin and unix?
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      slightly changed framework for sparc
+ * 29-Jun-02  Christian Tismer  <tismer@tismer.com>
+ *      Added register 13-29, 31 saves. The same way as
+ *      Armin Rigo did for the x86_unix version.
+ *      This seems to be now fully functional!
+ * 04-Mar-02  Hye-Shik Chang  <perky@fallin.lv>
+ *      Ported from i386.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#define STACK_MAGIC 3
+
+/* !!!!WARNING!!!! need to add "r31" in the next line if this header file
+ * is meant to be compiled non-dynamically!
+ */
+#define REGS_TO_SAVE "r13", "r14", "r15", "r16", "r17", "r18", "r19", "r20", \
+       "r21", "r22", "r23", "r24", "r25", "r26", "r27", "r28", "r29", \
+       "cr2", "cr3", "cr4"
+
+static int
+slp_switch(void)
+{
+    register int err;
+    register int *stackref, stsizediff;
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ ("; asm block 2\n\tmr %0, r1" : "=g" (stackref) : );
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ volatile (
+            "; asm block 3\n"
+            "\tmr r11, %0\n"
+            "\tadd r1, r1, r11\n"
+            "\tadd r30, r30, r11\n"
+            : /* no outputs */
+            : "g" (stsizediff)
+            : "r11"
+            );
+        SLP_RESTORE_STATE();
+    }
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("li %0, 0" : "=r" (err));
+    return err;
+}
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/*
+ * if you want to add self-inspection tools, place them
+ * here. See the x86_msvc for the necessary defines.
+ * These features are highly experimental und not
+ * essential yet.
+ */
diff --git a/src/greenlet/platform/switch_ppc_unix.h b/src/greenlet/platform/switch_ppc_unix.h
new file mode 100644
index 0000000..2b3d307
--- /dev/null
+++ b/src/greenlet/platform/switch_ppc_unix.h
@@ -0,0 +1,82 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 07-Sep-05 (py-dev mailing list discussion)
+ *      removed 'r31' from the register-saved.  !!!! WARNING !!!!
+ *      It means that this file can no longer be compiled statically!
+ *      It is now only suitable as part of a dynamic library!
+ * 14-Jan-04  Bob Ippolito <bob@redivi.com>
+ *      added cr2-cr4 to the registers to be saved.
+ *      Open questions: Should we save FP registers?
+ *      What about vector registers?
+ *      Differences between darwin and unix?
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 04-Oct-02  Gustavo Niemeyer <niemeyer@conectiva.com>
+ *      Ported from MacOS version.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      slightly changed framework for sparc
+ * 29-Jun-02  Christian Tismer  <tismer@tismer.com>
+ *      Added register 13-29, 31 saves. The same way as
+ *      Armin Rigo did for the x86_unix version.
+ *      This seems to be now fully functional!
+ * 04-Mar-02  Hye-Shik Chang  <perky@fallin.lv>
+ *      Ported from i386.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#define STACK_MAGIC 3
+
+/* !!!!WARNING!!!! need to add "r31" in the next line if this header file
+ * is meant to be compiled non-dynamically!
+ */
+#define REGS_TO_SAVE "r13", "r14", "r15", "r16", "r17", "r18", "r19", "r20", \
+       "r21", "r22", "r23", "r24", "r25", "r26", "r27", "r28", "r29", \
+       "cr2", "cr3", "cr4"
+static int
+slp_switch(void)
+{
+    register int err;
+    register int *stackref, stsizediff;
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ ("mr %0, 1" : "=g" (stackref) : );
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ volatile (
+            "mr 11, %0\n"
+            "add 1, 1, 11\n"
+            "add 30, 30, 11\n"
+            : /* no outputs */
+            : "g" (stsizediff)
+            : "11"
+            );
+        SLP_RESTORE_STATE();
+    }
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("li %0, 0" : "=r" (err));
+    return err;
+}
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/*
+ * if you want to add self-inspection tools, place them
+ * here. See the x86_msvc for the necessary defines.
+ * These features are highly experimental und not
+ * essential yet.
+ */
diff --git a/src/greenlet/platform/switch_riscv_unix.h b/src/greenlet/platform/switch_riscv_unix.h
new file mode 100644
index 0000000..5b5ea98
--- /dev/null
+++ b/src/greenlet/platform/switch_riscv_unix.h
@@ -0,0 +1,32 @@
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+#define STACK_MAGIC 0
+
+#define REGS_TO_SAVE "s0", "s1", "s2", "s3", "s4", "s5", \
+		     "s6", "s7", "s8", "s9", "s10", "s11", "fs0", "fs1", \
+		     "fs2", "fs3", "fs4", "fs5", "fs6", "fs7", "fs8", "fs9", \
+		     "fs10", "fs11"
+
+static int
+slp_switch(void)
+{
+  register int ret;
+  register long *stackref, stsizediff;
+  __asm__ volatile ("" : : : REGS_TO_SAVE);
+  __asm__ volatile ("mv %0, sp" : "=r" (stackref) : );
+  {
+      SLP_SAVE_STATE(stackref, stsizediff);
+      __asm__ volatile (
+	  "add sp, sp, %0\n\t"
+	  : /* no outputs */
+	  : "r" (stsizediff)
+	  );
+      SLP_RESTORE_STATE();
+  }
+  __asm__ volatile ("" : : : REGS_TO_SAVE);
+  __asm__ volatile ("mv %0, zero" : "=r" (ret) : );
+  return ret;
+}
+
+#endif
diff --git a/src/greenlet/platform/switch_s390_unix.h b/src/greenlet/platform/switch_s390_unix.h
new file mode 100644
index 0000000..6641854
--- /dev/null
+++ b/src/greenlet/platform/switch_s390_unix.h
@@ -0,0 +1,87 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 25-Jan-12  Alexey Borzenkov <snaury@gmail.com>
+ *      Fixed Linux/S390 port to work correctly with
+ *      different optimization options both on 31-bit
+ *      and 64-bit. Thanks to Stefan Raabe for lots
+ *      of testing.
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 06-Oct-02  Gustavo Niemeyer <niemeyer@conectiva.com>
+ *      Ported to Linux/S390.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#ifdef __s390x__
+#define STACK_MAGIC 20 /* 20 * 8 = 160 bytes of function call area */
+#else
+#define STACK_MAGIC 24 /* 24 * 4 = 96 bytes of function call area */
+#endif
+
+/* Technically, r11-r13 also need saving, but function prolog starts
+   with stm(g) and since there are so many saved registers already
+   it won't be optimized, resulting in all r6-r15 being saved */
+#define REGS_TO_SAVE "r6", "r7", "r8", "r9", "r10", "r14", \
+		     "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7", \
+		     "f8", "f9", "f10", "f11", "f12", "f13", "f14", "f15"
+
+static int
+slp_switch(void)
+{
+    register int ret;
+    register long *stackref, stsizediff;
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+#ifdef __s390x__
+    __asm__ volatile ("lgr %0, 15" : "=r" (stackref) : );
+#else
+    __asm__ volatile ("lr %0, 15" : "=r" (stackref) : );
+#endif
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+/* N.B.
+   r11 may be used as the frame pointer, and in that case it cannot be
+   clobbered and needs offsetting just like the stack pointer (but in cases
+   where frame pointer isn't used we might clobber it accidentally). What's
+   scary is that r11 is 2nd (and even 1st when GOT is used) callee saved
+   register that gcc would chose for surviving function calls. However,
+   since r6-r10 are clobbered above, their cost for reuse is reduced, so
+   gcc IRA will chose them over r11 (not seeing r11 is implicitly saved),
+   making it relatively safe to offset in all cases. :) */
+        __asm__ volatile (
+#ifdef __s390x__
+            "agr 15, %0\n\t"
+            "agr 11, %0"
+#else
+            "ar 15, %0\n\t"
+            "ar 11, %0"
+#endif
+            : /* no outputs */
+            : "r" (stsizediff)
+            );
+        SLP_RESTORE_STATE();
+    }
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("lhi %0, 0" : "=r" (ret) : );
+    return ret;
+}
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/* 
+ * if you want to add self-inspection tools, place them
+ * here. See the x86_msvc for the necessary defines.
+ * These features are highly experimental und not
+ * essential yet.
+ */
diff --git a/src/greenlet/platform/switch_sparc_sun_gcc.h b/src/greenlet/platform/switch_sparc_sun_gcc.h
new file mode 100644
index 0000000..652b57f
--- /dev/null
+++ b/src/greenlet/platform/switch_sparc_sun_gcc.h
@@ -0,0 +1,92 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 16-May-15  Alexey Borzenkov <snaury@gmail.com>
+ *      Move stack spilling code inside save/restore functions
+ * 30-Aug-13  Floris Bruynooghe <flub@devork.be>
+        Clean the register windows again before returning.
+        This does not clobber the PIC register as it leaves
+        the current window intact and is required for multi-
+        threaded code to work correctly.
+ * 08-Mar-11  Floris Bruynooghe <flub@devork.be>
+ *      No need to set return value register explicitly
+ *      before the stack and framepointer are adjusted
+ *      as none of the other registers are influenced by
+ *      this.  Also don't needlessly clean the windows
+ *      ('ta %0" :: "i" (ST_CLEAN_WINDOWS)') as that
+ *      clobbers the gcc PIC register (%l7).
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      added support for SunOS sparc with gcc
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+
+#define STACK_MAGIC 0
+
+
+#if defined(__sparcv9)
+#define SLP_FLUSHW __asm__ volatile ("flushw")
+#else
+#define SLP_FLUSHW __asm__ volatile ("ta 3") /* ST_FLUSH_WINDOWS */
+#endif
+
+/* On sparc we need to spill register windows inside save/restore functions */
+#define SLP_BEFORE_SAVE_STATE() SLP_FLUSHW
+#define SLP_BEFORE_RESTORE_STATE() SLP_FLUSHW
+
+
+static int
+slp_switch(void)
+{
+    register int err;
+    register int *stackref, stsizediff;
+
+    /* Put current stack pointer into stackref.
+     * Register spilling is done in save/restore.
+     */
+    __asm__ volatile ("mov %%sp, %0" : "=r" (stackref));
+
+    {
+        /* Thou shalt put SLP_SAVE_STATE into a local block */
+        /* Copy the current stack onto the heap */
+        SLP_SAVE_STATE(stackref, stsizediff);
+
+        /* Increment stack and frame pointer by stsizediff */
+        __asm__ volatile (
+            "add %0, %%sp, %%sp\n\t"
+            "add %0, %%fp, %%fp"
+            : : "r" (stsizediff));
+
+        /* Copy new stack from it's save store on the heap */
+        SLP_RESTORE_STATE();
+
+        __asm__ volatile ("mov %1, %0" : "=r" (err) : "i" (0));
+        return err;
+    }
+}
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/*
+ * if you want to add self-inspection tools, place them
+ * here. See the x86_msvc for the necessary defines.
+ * These features are highly experimental und not
+ * essential yet.
+ */
diff --git a/src/greenlet/platform/switch_x32_unix.h b/src/greenlet/platform/switch_x32_unix.h
new file mode 100644
index 0000000..cb14ec1
--- /dev/null
+++ b/src/greenlet/platform/switch_x32_unix.h
@@ -0,0 +1,63 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 17-Aug-12  Fantix King <fantix.king@gmail.com>
+ *      Ported from amd64.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#define STACK_MAGIC 0
+
+#define REGS_TO_SAVE "r12", "r13", "r14", "r15"
+
+
+static int
+slp_switch(void)
+{
+    void* ebp;
+    void* ebx;
+    unsigned int csr;
+    unsigned short cw;
+    register int err;
+    register int *stackref, stsizediff;
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("fstcw %0" : "=m" (cw));
+    __asm__ volatile ("stmxcsr %0" : "=m" (csr));
+    __asm__ volatile ("movl %%ebp, %0" : "=m" (ebp));
+    __asm__ volatile ("movl %%ebx, %0" : "=m" (ebx));
+    __asm__ ("movl %%esp, %0" : "=g" (stackref));
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ volatile (
+            "addl %0, %%esp\n"
+            "addl %0, %%ebp\n"
+            :
+            : "r" (stsizediff)
+            );
+        SLP_RESTORE_STATE();
+    }
+    __asm__ volatile ("movl %0, %%ebx" : : "m" (ebx));
+    __asm__ volatile ("movl %0, %%ebp" : : "m" (ebp));
+    __asm__ volatile ("ldmxcsr %0" : : "m" (csr));
+    __asm__ volatile ("fldcw %0" : : "m" (cw));
+    __asm__ volatile ("" : : : REGS_TO_SAVE);
+    __asm__ volatile ("xorl %%eax, %%eax" : "=a" (err));
+    return err;
+}
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/*
+ * if you want to add self-inspection tools, place them
+ * here. See the x86_msvc for the necessary defines.
+ * These features are highly experimental und not
+ * essential yet.
+ */
diff --git a/src/greenlet/platform/switch_x64_masm.asm b/src/greenlet/platform/switch_x64_masm.asm
new file mode 100644
index 0000000..f5c72a2
--- /dev/null
+++ b/src/greenlet/platform/switch_x64_masm.asm
@@ -0,0 +1,111 @@
+;
+; stack switching code for MASM on x641
+; Kristjan Valur Jonsson, sept 2005
+;
+
+
+;prototypes for our calls
+slp_save_state_asm PROTO
+slp_restore_state_asm PROTO
+
+
+pushxmm MACRO reg
+    sub rsp, 16
+    .allocstack 16
+    movaps [rsp], reg ; faster than movups, but we must be aligned
+    ; .savexmm128 reg, offset  (don't know what offset is, no documentation)
+ENDM
+popxmm MACRO reg
+    movaps reg, [rsp] ; faster than movups, but we must be aligned
+    add rsp, 16
+ENDM
+
+pushreg MACRO reg
+    push reg
+    .pushreg reg
+ENDM
+popreg MACRO reg
+    pop reg
+ENDM
+
+
+.code
+slp_switch PROC FRAME
+    ;realign stack to 16 bytes after return address push, makes the following faster
+    sub rsp,8
+    .allocstack 8
+
+    pushxmm xmm15
+    pushxmm xmm14
+    pushxmm xmm13
+    pushxmm xmm12
+    pushxmm xmm11
+    pushxmm xmm10
+    pushxmm xmm9
+    pushxmm xmm8
+    pushxmm xmm7
+    pushxmm xmm6
+
+    pushreg r15
+    pushreg r14
+    pushreg r13
+    pushreg r12
+
+    pushreg rbp
+    pushreg rbx
+    pushreg rdi
+    pushreg rsi
+
+    sub rsp, 10h ;allocate the singlefunction argument (must be multiple of 16)
+    .allocstack 10h
+.endprolog
+
+    lea rcx, [rsp+10h] ;load stack base that we are saving
+    call slp_save_state_asm ;pass stackpointer, return offset in eax
+    cmp rax, 1
+    je EXIT1
+    cmp rax, -1
+    je EXIT2
+    ;actual stack switch:
+    add rsp, rax
+    call slp_restore_state_asm
+    xor rax, rax ;return 0
+
+EXIT:
+
+    add rsp, 10h
+    popreg rsi
+    popreg rdi
+    popreg rbx
+    popreg rbp
+
+    popreg r12
+    popreg r13
+    popreg r14
+    popreg r15
+
+    popxmm xmm6
+    popxmm xmm7
+    popxmm xmm8
+    popxmm xmm9
+    popxmm xmm10
+    popxmm xmm11
+    popxmm xmm12
+    popxmm xmm13
+    popxmm xmm14
+    popxmm xmm15
+
+    add rsp, 8
+    ret
+
+EXIT1:
+    mov rax, 1
+    jmp EXIT
+
+EXIT2:
+    sar rax, 1
+    jmp EXIT
+
+slp_switch ENDP
+
+END
\ No newline at end of file
diff --git a/src/greenlet/platform/switch_x64_masm.obj b/src/greenlet/platform/switch_x64_masm.obj
new file mode 100644
index 0000000..64e3e6b
--- /dev/null
+++ b/src/greenlet/platform/switch_x64_masm.obj
diff --git a/src/greenlet/platform/switch_x64_msvc.h b/src/greenlet/platform/switch_x64_msvc.h
new file mode 100644
index 0000000..601ea56
--- /dev/null
+++ b/src/greenlet/platform/switch_x64_msvc.h
@@ -0,0 +1,60 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 26-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      again as a result of virtualized stack access,
+ *      the compiler used less registers. Needed to
+ *      explicit mention registers in order to get them saved.
+ *      Thanks to Jeff Senn for pointing this out and help.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      slightly changed framework for sparc
+ * 01-Mar-02  Christian Tismer  <tismer@tismer.com>
+ *      Initial final version after lots of iterations for i386.
+ */
+
+/* Avoid alloca redefined warning on mingw64 */
+#ifndef alloca
+#define alloca _alloca
+#endif
+
+#define STACK_REFPLUS 1
+#define STACK_MAGIC 0
+
+/* Use the generic support for an external assembly language slp_switch function. */
+#define EXTERNAL_ASM
+
+#ifdef SLP_EVAL
+/* This always uses the external masm assembly file. */
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/* we have IsBadReadPtr available, so we can peek at objects */
+/*
+#define STACKLESS_SPY
+
+#ifdef IMPLEMENT_STACKLESSMODULE
+#include "Windows.h"
+#define CANNOT_READ_MEM(p, bytes) IsBadReadPtr(p, bytes)
+
+static int IS_ON_STACK(void*p)
+{
+    int stackref;
+    intptr_t stackbase = ((intptr_t)&stackref) & 0xfffff000;
+    return (intptr_t)p >= stackbase && (intptr_t)p < stackbase + 0x00100000;
+}
+
+#endif
+*/
\ No newline at end of file
diff --git a/src/greenlet/platform/switch_x86_msvc.h b/src/greenlet/platform/switch_x86_msvc.h
new file mode 100644
index 0000000..010a22c
--- /dev/null
+++ b/src/greenlet/platform/switch_x86_msvc.h
@@ -0,0 +1,88 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 26-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      again as a result of virtualized stack access,
+ *      the compiler used less registers. Needed to
+ *      explicit mention registers in order to get them saved.
+ *      Thanks to Jeff Senn for pointing this out and help.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      slightly changed framework for sparc
+ * 01-Mar-02  Christian Tismer  <tismer@tismer.com>
+ *      Initial final version after lots of iterations for i386.
+ */
+
+#define alloca _alloca
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+#define STACK_MAGIC 0
+
+/* Some magic to quell warnings and keep slp_switch() from crashing when built
+   with VC90. Disable global optimizations, and the warning: frame pointer
+   register 'ebp' modified by inline assembly code */
+#pragma optimize("g", off)
+#pragma warning(disable:4731)
+
+static int
+slp_switch(void)
+{
+    void* seh;
+    register int *stackref, stsizediff;
+    __asm mov eax, fs:[0]
+    __asm mov [seh], eax
+    __asm mov stackref, esp;
+    /* modify EBX, ESI and EDI in order to get them preserved */
+    __asm mov ebx, ebx;
+    __asm xchg esi, edi;
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm {
+            mov     eax, stsizediff
+            add     esp, eax
+            add     ebp, eax
+        }
+        SLP_RESTORE_STATE();
+    }
+    __asm mov eax, [seh]
+    __asm mov fs:[0], eax
+    return 0;
+}
+
+/* re-enable ebp warning and global optimizations. */
+#pragma optimize("g", on)
+#pragma warning(default:4731)
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/* we have IsBadReadPtr available, so we can peek at objects */
+#define STACKLESS_SPY
+
+#ifdef IMPLEMENT_STACKLESSMODULE
+#include "Windows.h"
+#define CANNOT_READ_MEM(p, bytes) IsBadReadPtr(p, bytes)
+
+static int IS_ON_STACK(void*p)
+{
+    int stackref;
+    int stackbase = ((int)&stackref) & 0xfffff000;
+    return (int)p >= stackbase && (int)p < stackbase + 0x00100000;
+} 
+
+#endif
diff --git a/src/greenlet/platform/switch_x86_unix.h b/src/greenlet/platform/switch_x86_unix.h
new file mode 100644
index 0000000..3a95186
--- /dev/null
+++ b/src/greenlet/platform/switch_x86_unix.h
@@ -0,0 +1,105 @@
+/*
+ * this is the internal transfer function.
+ *
+ * HISTORY
+ * 3-May-13   Ralf Schmitt  <ralf@systemexit.de>
+ *     Add support for strange GCC caller-save decisions
+ *     (ported from switch_aarch64_gcc.h)
+ * 19-Aug-11  Alexey Borzenkov  <snaury@gmail.com>
+ *      Correctly save ebp, ebx and cw
+ * 07-Sep-05 (py-dev mailing list discussion)
+ *      removed 'ebx' from the register-saved.  !!!! WARNING !!!!
+ *      It means that this file can no longer be compiled statically!
+ *      It is now only suitable as part of a dynamic library!
+ * 24-Nov-02  Christian Tismer  <tismer@tismer.com>
+ *      needed to add another magic constant to insure
+ *      that f in slp_eval_frame(PyFrameObject *f)
+ *      STACK_REFPLUS will probably be 1 in most cases.
+ *      gets included into the saved stack area.
+ * 17-Sep-02  Christian Tismer  <tismer@tismer.com>
+ *      after virtualizing stack save/restore, the
+ *      stack size shrunk a bit. Needed to introduce
+ *      an adjustment STACK_MAGIC per platform.
+ * 15-Sep-02  Gerd Woetzel       <gerd.woetzel@GMD.DE>
+ *      slightly changed framework for spark
+ * 31-Avr-02  Armin Rigo         <arigo@ulb.ac.be>
+ *      Added ebx, esi and edi register-saves.
+ * 01-Mar-02  Samual M. Rushing  <rushing@ironport.com>
+ *      Ported from i386.
+ */
+
+#define STACK_REFPLUS 1
+
+#ifdef SLP_EVAL
+
+/* #define STACK_MAGIC 3 */
+/* the above works fine with gcc 2.96, but 2.95.3 wants this */
+#define STACK_MAGIC 0
+
+#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
+# define ATTR_NOCLONE __attribute__((noclone))
+#else
+# define ATTR_NOCLONE
+#endif
+
+static int
+slp_switch(void)
+{
+    int err;
+#ifdef _WIN32
+    void *seh;
+#endif
+    void *ebp, *ebx;
+    unsigned short cw;
+    register int *stackref, stsizediff;
+    __asm__ volatile ("" : : : "esi", "edi");
+    __asm__ volatile ("fstcw %0" : "=m" (cw));
+    __asm__ volatile ("movl %%ebp, %0" : "=m" (ebp));
+    __asm__ volatile ("movl %%ebx, %0" : "=m" (ebx));
+#ifdef _WIN32
+    __asm__ volatile (
+        "movl %%fs:0x0, %%eax\n"
+        "movl %%eax, %0\n"
+        : "=m" (seh)
+        :
+        : "eax");
+#endif
+    __asm__ ("movl %%esp, %0" : "=g" (stackref));
+    {
+        SLP_SAVE_STATE(stackref, stsizediff);
+        __asm__ volatile (
+            "addl %0, %%esp\n"
+            "addl %0, %%ebp\n"
+            :
+            : "r" (stsizediff)
+            );
+        SLP_RESTORE_STATE();
+        __asm__ volatile ("xorl %%eax, %%eax" : "=a" (err));
+    }
+#ifdef _WIN32
+    __asm__ volatile (
+        "movl %0, %%eax\n"
+        "movl %%eax, %%fs:0x0\n"
+        :
+        : "m" (seh)
+        : "eax");
+#endif
+    __asm__ volatile ("movl %0, %%ebx" : : "m" (ebx));
+    __asm__ volatile ("movl %0, %%ebp" : : "m" (ebp));
+    __asm__ volatile ("fldcw %0" : : "m" (cw));
+    __asm__ volatile ("" : : : "esi", "edi");
+    return err;
+}
+
+#endif
+
+/*
+ * further self-processing support
+ */
+
+/* 
+ * if you want to add self-inspection tools, place them
+ * here. See the x86_msvc for the necessary defines.
+ * These features are highly experimental und not
+ * essential yet.
+ */
diff --git a/src/greenlet/slp_platformselect.h b/src/greenlet/slp_platformselect.h
new file mode 100644
index 0000000..b5e8eb6
--- /dev/null
+++ b/src/greenlet/slp_platformselect.h
@@ -0,0 +1,58 @@
+/*
+ * Platform Selection for Stackless Python
+ */
+
+#if   defined(MS_WIN32) && !defined(MS_WIN64) && defined(_M_IX86) && defined(_MSC_VER)
+#include "platform/switch_x86_msvc.h" /* MS Visual Studio on X86 */
+#elif defined(MS_WIN64) && defined(_M_X64) && defined(_MSC_VER) || defined(__MINGW64__)
+#include "platform/switch_x64_msvc.h" /* MS Visual Studio on X64 */
+#elif defined(__GNUC__) && defined(__amd64__) && defined(__ILP32__)
+#include "platform/switch_x32_unix.h" /* gcc on amd64 with x32 ABI */
+#elif defined(__GNUC__) && defined(__amd64__)
+#include "platform/switch_amd64_unix.h" /* gcc on amd64 */
+#elif defined(__GNUC__) && defined(__i386__)
+#include "platform/switch_x86_unix.h" /* gcc on X86 */
+#elif defined(__GNUC__) && defined(__powerpc64__) && (defined(__linux__) || defined(__FreeBSD__))
+#include "platform/switch_ppc64_linux.h" /* gcc on PowerPC 64-bit */
+#elif defined(__GNUC__) && defined(__PPC__) && (defined(__linux__) || defined(__FreeBSD__))
+#include "platform/switch_ppc_linux.h" /* gcc on PowerPC */
+#elif defined(__GNUC__) && defined(__ppc__) && defined(__APPLE__)
+#include "platform/switch_ppc_macosx.h" /* Apple MacOS X on PowerPC */
+#elif defined(__GNUC__) && defined(__powerpc64__) && defined(_AIX)
+#include "platform/switch_ppc64_aix.h" /* gcc on AIX/PowerPC 64-bit */
+#elif defined(__GNUC__) && defined(_ARCH_PPC) && defined(_AIX)
+#include "platform/switch_ppc_aix.h" /* gcc on AIX/PowerPC */
+#elif defined(__GNUC__) && defined(sparc)
+#include "platform/switch_sparc_sun_gcc.h" /* SunOS sparc with gcc */
+#elif defined(__SUNPRO_C) && defined(sparc) && defined(sun)
+#include "platform/switch_sparc_sun_gcc.h" /* SunStudio on amd64 */
+#elif defined(__SUNPRO_C) && defined(__amd64__) && defined(sun)
+#include "platform/switch_amd64_unix.h" /* SunStudio on amd64 */
+#elif defined(__SUNPRO_C) && defined(__i386__) && defined(sun)
+#include "platform/switch_x86_unix.h" /* SunStudio on x86 */
+#elif defined(__GNUC__) && defined(__s390__) && defined(__linux__)
+#include "platform/switch_s390_unix.h"	/* Linux/S390 */
+#elif defined(__GNUC__) && defined(__s390x__) && defined(__linux__)
+#include "platform/switch_s390_unix.h"	/* Linux/S390 zSeries (64-bit) */
+#elif defined(__GNUC__) && defined(__arm__)
+#ifdef __APPLE__
+#include <TargetConditionals.h>
+#endif
+#if TARGET_OS_IPHONE
+#include "platform/switch_arm32_ios.h" /* iPhone OS on arm32 */
+#else
+#include "platform/switch_arm32_gcc.h" /* gcc using arm32 */
+#endif
+#elif defined(__GNUC__) && defined(__mips__) && defined(__linux__)
+#include "platform/switch_mips_unix.h" /* Linux/MIPS */
+#elif defined(__GNUC__) && defined(__aarch64__)
+#include "platform/switch_aarch64_gcc.h" /* Aarch64 ABI */
+#elif defined(__GNUC__) && defined(__mc68000__)
+#include "platform/switch_m68k_gcc.h" /* gcc on m68k */
+#elif defined(__GNUC__) && defined(__csky__)
+#include "platform/switch_csky_gcc.h" /* gcc on csky */
+#elif defined(__GNUC__) && defined(__riscv)
+#include "platform/switch_riscv_unix.h" /* gcc on RISC-V */
+#elif defined(__GNUC__) && defined(__alpha__)
+#include "platform/switch_alpha_unix.h" /* gcc on DEC Alpha */
+#endif
diff --git a/src/greenlet/tests/__init__.py b/src/greenlet/tests/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/src/greenlet/tests/__init__.py
diff --git a/src/greenlet/tests/_test_extension.c b/src/greenlet/tests/_test_extension.c
new file mode 100644
index 0000000..ec8b70c
--- /dev/null
+++ b/src/greenlet/tests/_test_extension.c
@@ -0,0 +1,208 @@
+/* This is a set of functions used by test_extension_interface.py to test the
+ * Greenlet C API.
+ */
+
+#include "../greenlet.h"
+
+#ifndef Py_RETURN_NONE
+#define Py_RETURN_NONE return Py_INCREF(Py_None), Py_None
+#endif
+
+#define TEST_MODULE_NAME "_test_extension"
+
+static PyObject *
+test_switch(PyObject *self, PyObject *greenlet)
+{
+	PyObject *result = NULL;
+
+	if (greenlet == NULL || !PyGreenlet_Check(greenlet)) {
+		PyErr_BadArgument();
+		return NULL;
+	}
+
+	result = PyGreenlet_Switch((PyGreenlet *) greenlet, NULL, NULL);
+	if (result == NULL) {
+		if (!PyErr_Occurred()) {
+			PyErr_SetString(
+				PyExc_AssertionError,
+				"greenlet.switch() failed for some reason.");
+		}
+		return NULL;
+	}
+	Py_INCREF(result);
+	return result;
+}
+
+static PyObject *
+test_switch_kwargs(PyObject *self, PyObject *args, PyObject *kwargs)
+{
+	PyGreenlet *g = NULL;
+	PyObject *result = NULL;
+
+	PyArg_ParseTuple(args, "O!", &PyGreenlet_Type, &g);
+
+	if (g == NULL || !PyGreenlet_Check(g)) {
+		PyErr_BadArgument();
+		return NULL;
+	}
+
+	result = PyGreenlet_Switch(g, NULL, kwargs);
+	if (result == NULL) {
+		if (!PyErr_Occurred()) {
+			PyErr_SetString(
+				PyExc_AssertionError,
+				"greenlet.switch() failed for some reason.");
+		}
+		return NULL;
+	}
+	Py_XINCREF(result);
+	return result;
+}
+
+static PyObject *
+test_getcurrent(PyObject *self)
+{
+	PyGreenlet *g = PyGreenlet_GetCurrent();
+	if (g == NULL || !PyGreenlet_Check(g) || !PyGreenlet_ACTIVE(g)) {
+		PyErr_SetString(
+			PyExc_AssertionError,
+			"getcurrent() returned an invalid greenlet");
+		Py_XDECREF(g);
+		return NULL;
+	}
+	Py_DECREF(g);
+	Py_RETURN_NONE;
+}
+
+static PyObject *
+test_setparent(PyObject *self, PyObject *arg)
+{
+	PyGreenlet *current;
+	PyGreenlet *greenlet = NULL;
+
+	if (arg == NULL || !PyGreenlet_Check(arg))
+	{
+		PyErr_BadArgument();
+		return NULL;
+	}
+	if ((current = PyGreenlet_GetCurrent()) == NULL) {
+		return NULL;
+	}
+	greenlet = (PyGreenlet *) arg;
+	if (PyGreenlet_SetParent(greenlet, current)) {
+		Py_DECREF(current);
+		return NULL;
+	}
+	Py_DECREF(current);
+	if (PyGreenlet_Switch(greenlet, NULL, NULL) == NULL) {
+		return NULL;
+	}
+	Py_RETURN_NONE;
+}
+
+static PyObject *
+test_new_greenlet(PyObject *self, PyObject *callable)
+{
+	PyObject *result = NULL;
+	PyGreenlet *greenlet = PyGreenlet_New(callable, NULL);
+
+	if (!greenlet) {
+		return NULL;
+	}
+
+	result = PyGreenlet_Switch(greenlet, NULL, NULL);
+	if (result == NULL) {
+		return NULL;
+	}
+
+	Py_INCREF(result);
+	return result;
+}
+
+static PyObject *
+test_raise_dead_greenlet(PyObject *self)
+{
+	PyErr_SetString(PyExc_GreenletExit, "test GreenletExit exception.");
+	return NULL;
+}
+
+static PyObject *
+test_raise_greenlet_error(PyObject *self)
+{
+	PyErr_SetString(PyExc_GreenletError, "test greenlet.error exception");
+	return NULL;
+}
+
+static PyObject *
+test_throw(PyObject *self, PyGreenlet *g)
+{
+	const char msg[] = "take that sucka!";
+	PyObject *msg_obj = Py_BuildValue("s", msg);
+	PyGreenlet_Throw(g, PyExc_ValueError, msg_obj, NULL);
+	Py_DECREF(msg_obj);
+	Py_RETURN_NONE;
+}
+
+static PyMethodDef test_methods[] = {
+	{"test_switch", (PyCFunction) test_switch, METH_O,
+	 "Switch to the provided greenlet sending provided arguments, and \n"
+	 "return the results."},
+	{"test_switch_kwargs", (PyCFunction) test_switch_kwargs,
+	 METH_VARARGS | METH_KEYWORDS,
+	 "Switch to the provided greenlet sending the provided keyword args."},
+	{"test_getcurrent", (PyCFunction) test_getcurrent, METH_NOARGS,
+	 "Test PyGreenlet_GetCurrent()"},
+	{"test_setparent", (PyCFunction) test_setparent, METH_O,
+	 "Se the parent of the provided greenlet and switch to it."},
+	{"test_new_greenlet", (PyCFunction) test_new_greenlet, METH_O,
+	 "Test PyGreenlet_New()"},
+	{"test_raise_dead_greenlet", (PyCFunction) test_raise_dead_greenlet,
+	 METH_NOARGS, "Just raise greenlet.GreenletExit"},
+	{"test_raise_greenlet_error", (PyCFunction) test_raise_greenlet_error,
+	 METH_NOARGS, "Just raise greenlet.error"},
+	{"test_throw", (PyCFunction) test_throw, METH_O,
+	 "Throw a ValueError at the provided greenlet"},
+	{NULL, NULL, 0, NULL}
+};
+
+#if PY_MAJOR_VERSION >= 3
+#define INITERROR return NULL
+
+static struct PyModuleDef moduledef = {
+	PyModuleDef_HEAD_INIT,
+	TEST_MODULE_NAME,
+	NULL,
+	0,
+	test_methods,
+	NULL,
+	NULL,
+	NULL,
+	NULL
+};
+
+PyMODINIT_FUNC
+PyInit__test_extension(void)
+#else
+#define INITERROR return
+PyMODINIT_FUNC
+init_test_extension(void)
+#endif
+{
+	PyObject *module = NULL;
+
+#if PY_MAJOR_VERSION >= 3
+	module = PyModule_Create(&moduledef);
+#else
+	module = Py_InitModule(TEST_MODULE_NAME, test_methods);
+#endif
+
+	if (module == NULL) {
+		INITERROR;
+	}
+
+	PyGreenlet_Import();
+
+#if PY_MAJOR_VERSION >= 3
+	return module;
+#endif
+}
diff --git a/src/greenlet/tests/_test_extension_cpp.cpp b/src/greenlet/tests/_test_extension_cpp.cpp
new file mode 100644
index 0000000..fc3adad
--- /dev/null
+++ b/src/greenlet/tests/_test_extension_cpp.cpp
@@ -0,0 +1,118 @@
+/* This is a set of functions used to test C++ exceptions are not
+ * broken during greenlet switches
+ */
+
+#include "../greenlet.h"
+
+struct exception_t
+{
+	int depth;
+	exception_t(int depth) : depth(depth) { }
+};
+
+/* Functions are called via pointers to prevent inlining */
+static void (*p_test_exception_throw)(int depth);
+static PyObject* (*p_test_exception_switch_recurse)(int depth, int left);
+
+static void test_exception_throw(int depth)
+{
+	throw exception_t(depth);
+}
+
+static PyObject* test_exception_switch_recurse(int depth, int left)
+{
+	if (left > 0) {
+		return p_test_exception_switch_recurse(depth, left - 1);
+	}
+
+	PyObject* result = NULL;
+	PyGreenlet* self = PyGreenlet_GetCurrent();
+	if (self == NULL)
+		return NULL;
+
+	try {
+		PyGreenlet_Switch(self->parent, NULL, NULL);
+		p_test_exception_throw(depth);
+		PyErr_SetString(PyExc_RuntimeError, "throwing C++ exception didn't work");
+	} catch(exception_t& e) {
+		if (e.depth != depth)
+			PyErr_SetString(PyExc_AssertionError, "depth mismatch");
+		else
+			result = PyLong_FromLong(depth);
+	} catch(...) {
+		PyErr_SetString(PyExc_RuntimeError, "unexpected C++ exception");
+	}
+
+	Py_DECREF(self);
+	return result;
+}
+
+/* test_exception_switch(int depth)
+ * - recurses depth times
+ * - switches to parent inside try/catch block
+ * - throws an exception that (expected to be caught in the same function)
+ * - verifies depth matches (exceptions shouldn't be caught in other greenlets)
+ */
+static PyObject *
+test_exception_switch(PyObject *self, PyObject *args)
+{
+	int depth;
+	if (!PyArg_ParseTuple(args, "i", &depth))
+		return NULL;
+	return p_test_exception_switch_recurse(depth, depth);
+}
+
+static PyMethodDef test_methods[] = {
+	{"test_exception_switch", (PyCFunction)&test_exception_switch, METH_VARARGS,
+	 "Switches to parent twice, to test exception handling and greenlet switching."},
+	{NULL, NULL, 0, NULL}
+};
+
+
+#if PY_MAJOR_VERSION >= 3
+#define INITERROR return NULL
+
+static struct PyModuleDef moduledef = {
+	PyModuleDef_HEAD_INIT,
+	"greenlet.tests._test_extension_cpp",
+	NULL,
+	0,
+	test_methods,
+	NULL,
+	NULL,
+	NULL,
+	NULL
+};
+
+PyMODINIT_FUNC
+PyInit__test_extension_cpp(void)
+#else
+#define INITERROR return
+PyMODINIT_FUNC
+init_test_extension_cpp(void)
+#endif
+{
+	PyObject *module = NULL;
+
+#if PY_MAJOR_VERSION >= 3
+	module = PyModule_Create(&moduledef);
+#else
+	module = Py_InitModule("greenlet.tests._test_extension_cpp", test_methods);
+#endif
+
+	if (module == NULL) {
+		INITERROR;
+	}
+
+	PyGreenlet_Import();
+	if (_PyGreenlet_API == NULL) {
+		INITERROR;
+	}
+
+	p_test_exception_throw = test_exception_throw;
+	p_test_exception_switch_recurse = test_exception_switch_recurse;
+
+#if PY_MAJOR_VERSION >= 3
+	return module;
+#endif
+}
diff --git a/src/greenlet/tests/test_contextvars.py b/src/greenlet/tests/test_contextvars.py
new file mode 100644
index 0000000..49b7c0d
--- /dev/null
+++ b/src/greenlet/tests/test_contextvars.py
@@ -0,0 +1,266 @@
+import unittest
+import gc
+import sys
+
+from functools import partial
+
+from greenlet import greenlet
+from greenlet import getcurrent
+
+
+try:
+    from contextvars import Context
+    from contextvars import ContextVar
+    from contextvars import copy_context
+except ImportError:
+    Context = ContextVar = copy_context = None
+
+# We don't support testing if greenlet's built-in context var support is disabled.
+@unittest.skipUnless(Context is not None, "ContextVar not supported")
+class ContextVarsTests(unittest.TestCase):
+    def _new_ctx_run(self, *args, **kwargs):
+        return copy_context().run(*args, **kwargs)
+
+    def _increment(self, greenlet_id, ctx_var, callback, counts, expect):
+        if expect is None:
+            self.assertIsNone(ctx_var.get())
+        else:
+            self.assertEqual(ctx_var.get(), expect)
+        ctx_var.set(greenlet_id)
+        for _ in range(2):
+            counts[ctx_var.get()] += 1
+            callback()
+
+    def _test_context(self, propagate_by):
+        id_var = ContextVar("id", default=None)
+        id_var.set(0)
+
+        callback = getcurrent().switch
+        counts = dict((i, 0) for i in range(5))
+
+        lets = [
+            greenlet(partial(
+                partial(
+                    copy_context().run,
+                    self._increment
+                ) if propagate_by == "run" else self._increment,
+                greenlet_id=i,
+                ctx_var=id_var,
+                callback=callback,
+                counts=counts,
+                expect=(
+                    i - 1 if propagate_by == "share" else
+                    0 if propagate_by in ("set", "run") else None
+                )
+            ))
+            for i in range(1, 5)
+        ]
+
+        for let in lets:
+            if propagate_by == "set":
+                let.gr_context = copy_context()
+            elif propagate_by == "share":
+                let.gr_context = getcurrent().gr_context
+
+        for i in range(2):
+            counts[id_var.get()] += 1
+            for let in lets:
+                let.switch()
+
+        if propagate_by == "run":
+            # Must leave each context.run() in reverse order of entry
+            for let in reversed(lets):
+                let.switch()
+        else:
+            # No context.run(), so fine to exit in any order.
+            for let in lets:
+                let.switch()
+
+        for let in lets:
+            self.assertTrue(let.dead)
+            # When using run(), we leave the run() as the greenlet dies,
+            # and there's no context "underneath". When not using run(),
+            # gr_context still reflects the context the greenlet was
+            # running in.
+            self.assertEqual(let.gr_context is None, propagate_by == "run")
+
+        if propagate_by == "share":
+            self.assertEqual(counts, {0: 1, 1: 1, 2: 1, 3: 1, 4: 6})
+        else:
+            self.assertEqual(set(counts.values()), set([2]))
+
+    def test_context_propagated_by_context_run(self):
+        self._new_ctx_run(self._test_context, "run")
+
+    def test_context_propagated_by_setting_attribute(self):
+        self._new_ctx_run(self._test_context, "set")
+
+    def test_context_not_propagated(self):
+        self._new_ctx_run(self._test_context, None)
+
+    def test_context_shared(self):
+        self._new_ctx_run(self._test_context, "share")
+
+    def test_break_ctxvars(self):
+        let1 = greenlet(copy_context().run)
+        let2 = greenlet(copy_context().run)
+        let1.switch(getcurrent().switch)
+        let2.switch(getcurrent().switch)
+        # Since let2 entered the current context and let1 exits its own, the
+        # interpreter emits:
+        # RuntimeError: cannot exit context: thread state references a different context object
+        let1.switch()
+
+    def test_not_broken_if_using_attribute_instead_of_context_run(self):
+        let1 = greenlet(getcurrent().switch)
+        let2 = greenlet(getcurrent().switch)
+        let1.gr_context = copy_context()
+        let2.gr_context = copy_context()
+        let1.switch()
+        let2.switch()
+        let1.switch()
+        let2.switch()
+
+    def test_context_assignment_while_running(self):
+        id_var = ContextVar("id", default=None)
+
+        def target():
+            self.assertIsNone(id_var.get())
+            self.assertIsNone(gr.gr_context)
+
+            # Context is created on first use
+            id_var.set(1)
+            self.assertIsInstance(gr.gr_context, Context)
+            self.assertEqual(id_var.get(), 1)
+            self.assertEqual(gr.gr_context[id_var], 1)
+
+            # Clearing the context makes it get re-created as another
+            # empty context when next used
+            old_context = gr.gr_context
+            gr.gr_context = None  # assign None while running
+            self.assertIsNone(id_var.get())
+            self.assertIsNone(gr.gr_context)
+            id_var.set(2)
+            self.assertIsInstance(gr.gr_context, Context)
+            self.assertEqual(id_var.get(), 2)
+            self.assertEqual(gr.gr_context[id_var], 2)
+
+            new_context = gr.gr_context
+            getcurrent().parent.switch((old_context, new_context))
+            # parent switches us back to old_context
+
+            self.assertEqual(id_var.get(), 1)
+            gr.gr_context = new_context  # assign non-None while running
+            self.assertEqual(id_var.get(), 2)
+
+            getcurrent().parent.switch()
+            # parent switches us back to no context
+            self.assertIsNone(id_var.get())
+            self.assertIsNone(gr.gr_context)
+            gr.gr_context = old_context
+            self.assertEqual(id_var.get(), 1)
+
+            getcurrent().parent.switch()
+            # parent switches us back to no context
+            self.assertIsNone(id_var.get())
+            self.assertIsNone(gr.gr_context)
+
+        gr = greenlet(target)
+
+        with self.assertRaisesRegex(AttributeError, "can't delete attr"):
+            del gr.gr_context
+
+        self.assertIsNone(gr.gr_context)
+        old_context, new_context = gr.switch()
+        self.assertIs(new_context, gr.gr_context)
+        self.assertEqual(old_context[id_var], 1)
+        self.assertEqual(new_context[id_var], 2)
+        self.assertEqual(new_context.run(id_var.get), 2)
+        gr.gr_context = old_context  # assign non-None while suspended
+        gr.switch()
+        self.assertIs(gr.gr_context, new_context)
+        gr.gr_context = None  # assign None while suspended
+        gr.switch()
+        self.assertIs(gr.gr_context, old_context)
+        gr.gr_context = None
+        gr.switch()
+        self.assertIsNone(gr.gr_context)
+
+        # Make sure there are no reference leaks
+        gr = None
+        gc.collect()
+        self.assertEqual(sys.getrefcount(old_context), 2)
+        self.assertEqual(sys.getrefcount(new_context), 2)
+
+    def test_context_assignment_different_thread(self):
+        import threading
+
+        ctx = Context()
+        var = ContextVar("var", default=None)
+        is_running = threading.Event()
+        should_suspend = threading.Event()
+        did_suspend = threading.Event()
+        should_exit = threading.Event()
+        holder = []
+
+        def greenlet_in_thread_fn():
+            var.set(1)
+            is_running.set()
+            should_suspend.wait()
+            var.set(2)
+            getcurrent().parent.switch()
+            holder.append(var.get())
+
+        def thread_fn():
+            gr = greenlet(greenlet_in_thread_fn)
+            gr.gr_context = ctx
+            holder.append(gr)
+            gr.switch()
+            did_suspend.set()
+            should_exit.wait()
+            gr.switch()
+
+        thread = threading.Thread(target=thread_fn, daemon=True)
+        thread.start()
+        is_running.wait()
+        gr = holder[0]
+
+        # Can't access or modify context if the greenlet is running
+        # in a different thread
+        with self.assertRaisesRegex(ValueError, "running in a different"):
+            getattr(gr, 'gr_context')
+        with self.assertRaisesRegex(ValueError, "running in a different"):
+            gr.gr_context = None
+
+        should_suspend.set()
+        did_suspend.wait()
+
+        # OK to access and modify context if greenlet is suspended
+        self.assertIs(gr.gr_context, ctx)
+        self.assertEqual(gr.gr_context[var], 2)
+        gr.gr_context = None
+
+        should_exit.set()
+        thread.join()
+
+        self.assertEqual(holder, [gr, None])
+
+        # Context can still be accessed/modified when greenlet is dead:
+        self.assertIsNone(gr.gr_context)
+        gr.gr_context = ctx
+        self.assertIs(gr.gr_context, ctx)
+
+@unittest.skipIf(Context is not None, "ContextVar supported")
+class NoContextVarsTests(unittest.TestCase):
+    def test_contextvars_errors(self):
+        let1 = greenlet(getcurrent().switch)
+        self.assertFalse(hasattr(let1, 'gr_context'))
+        with self.assertRaises(AttributeError):
+            getattr(let1, 'gr_context')
+        with self.assertRaises(AttributeError):
+            let1.gr_context = None
+        let1.switch()
+        with self.assertRaises(AttributeError):
+            getattr(let1, 'gr_context')
+        with self.assertRaises(AttributeError):
+            let1.gr_context = None
diff --git a/src/greenlet/tests/test_cpp.py b/src/greenlet/tests/test_cpp.py
new file mode 100644
index 0000000..741ea10
--- /dev/null
+++ b/src/greenlet/tests/test_cpp.py
@@ -0,0 +1,18 @@
+from __future__ import print_function
+from __future__ import absolute_import
+
+import unittest
+
+import greenlet
+from . import _test_extension_cpp
+
+
+class CPPTests(unittest.TestCase):
+    def test_exception_switch(self):
+        greenlets = []
+        for i in range(4):
+            g = greenlet.greenlet(_test_extension_cpp.test_exception_switch)
+            g.switch(i)
+            greenlets.append(g)
+        for i, g in enumerate(greenlets):
+            self.assertEqual(g.switch(), i)
diff --git a/src/greenlet/tests/test_extension_interface.py b/src/greenlet/tests/test_extension_interface.py
new file mode 100644
index 0000000..bc87452
--- /dev/null
+++ b/src/greenlet/tests/test_extension_interface.py
@@ -0,0 +1,74 @@
+from __future__ import print_function
+from __future__ import absolute_import
+
+import sys
+import unittest
+
+import greenlet
+from . import _test_extension
+
+
+class CAPITests(unittest.TestCase):
+    def test_switch(self):
+        self.assertEqual(
+            50, _test_extension.test_switch(greenlet.greenlet(lambda: 50)))
+
+    def test_switch_kwargs(self):
+        def foo(x, y):
+            return x * y
+        g = greenlet.greenlet(foo)
+        self.assertEqual(6, _test_extension.test_switch_kwargs(g, x=3, y=2))
+
+    def test_setparent(self):
+        def foo():
+            def bar():
+                greenlet.getcurrent().parent.switch()
+
+                # This final switch should go back to the main greenlet, since
+                # the test_setparent() function in the C extension should have
+                # reparented this greenlet.
+                greenlet.getcurrent().parent.switch()
+                raise AssertionError("Should never have reached this code")
+            child = greenlet.greenlet(bar)
+            child.switch()
+            greenlet.getcurrent().parent.switch(child)
+            greenlet.getcurrent().parent.throw(
+                AssertionError("Should never reach this code"))
+        foo_child = greenlet.greenlet(foo).switch()
+        self.assertEqual(None, _test_extension.test_setparent(foo_child))
+
+    def test_getcurrent(self):
+        _test_extension.test_getcurrent()
+
+    def test_new_greenlet(self):
+        self.assertEqual(-15, _test_extension.test_new_greenlet(lambda: -15))
+
+    def test_raise_greenlet_dead(self):
+        self.assertRaises(
+            greenlet.GreenletExit, _test_extension.test_raise_dead_greenlet)
+
+    def test_raise_greenlet_error(self):
+        self.assertRaises(
+            greenlet.error, _test_extension.test_raise_greenlet_error)
+
+    def test_throw(self):
+        seen = []
+
+        def foo():
+            try:
+                greenlet.getcurrent().parent.switch()
+            except ValueError:
+                seen.append(sys.exc_info()[1])
+            except greenlet.GreenletExit:
+                raise AssertionError
+        g = greenlet.greenlet(foo)
+        g.switch()
+        _test_extension.test_throw(g)
+        self.assertEqual(len(seen), 1)
+        self.assertTrue(
+            isinstance(seen[0], ValueError),
+            "ValueError was not raised in foo()")
+        self.assertEqual(
+            str(seen[0]),
+            'take that sucka!',
+            "message doesn't match")
diff --git a/src/greenlet/tests/test_gc.py b/src/greenlet/tests/test_gc.py
new file mode 100644
index 0000000..a2a41ca
--- /dev/null
+++ b/src/greenlet/tests/test_gc.py
@@ -0,0 +1,77 @@
+import gc
+import sys
+import unittest
+import weakref
+
+import greenlet
+
+
+class GCTests(unittest.TestCase):
+    def test_dead_circular_ref(self):
+        o = weakref.ref(greenlet.greenlet(greenlet.getcurrent).switch())
+        gc.collect()
+        self.assertTrue(o() is None)
+        self.assertFalse(gc.garbage, gc.garbage)
+
+    if greenlet.GREENLET_USE_GC:
+        # These only work with greenlet gc support
+
+        def test_circular_greenlet(self):
+            class circular_greenlet(greenlet.greenlet):
+                pass
+            o = circular_greenlet()
+            o.self = o
+            o = weakref.ref(o)
+            gc.collect()
+            self.assertTrue(o() is None)
+            self.assertFalse(gc.garbage, gc.garbage)
+
+        def test_inactive_ref(self):
+            class inactive_greenlet(greenlet.greenlet):
+                def __init__(self):
+                    greenlet.greenlet.__init__(self, run=self.run)
+
+                def run(self):
+                    pass
+            o = inactive_greenlet()
+            o = weakref.ref(o)
+            gc.collect()
+            self.assertTrue(o() is None)
+            self.assertFalse(gc.garbage, gc.garbage)
+
+        def test_finalizer_crash(self):
+            # This test is designed to crash when active greenlets
+            # are made garbage collectable, until the underlying
+            # problem is resolved. How does it work:
+            # - order of object creation is important
+            # - array is created first, so it is moved to unreachable first
+            # - we create a cycle between a greenlet and this array
+            # - we create an object that participates in gc, is only
+            #   referenced by a greenlet, and would corrupt gc lists
+            #   on destruction, the easiest is to use an object with
+            #   a finalizer
+            # - because array is the first object in unreachable it is
+            #   cleared first, which causes all references to greenlet
+            #   to disappear and causes greenlet to be destroyed, but since
+            #   it is still live it causes a switch during gc, which causes
+            #   an object with finalizer to be destroyed, which causes stack
+            #   corruption and then a crash
+            class object_with_finalizer(object):
+                def __del__(self):
+                    pass
+            array = []
+            parent = greenlet.getcurrent()
+            def greenlet_body():
+                greenlet.getcurrent().object = object_with_finalizer()
+                try:
+                    parent.switch()
+                finally:
+                    del greenlet.getcurrent().object
+            g = greenlet.greenlet(greenlet_body)
+            g.array = array
+            array.append(g)
+            g.switch()
+            del array
+            del g
+            greenlet.getcurrent()
+            gc.collect()
diff --git a/src/greenlet/tests/test_generator.py b/src/greenlet/tests/test_generator.py
new file mode 100644
index 0000000..62f9f26
--- /dev/null
+++ b/src/greenlet/tests/test_generator.py
@@ -0,0 +1,59 @@
+import unittest
+from greenlet import greenlet
+
+
+class genlet(greenlet):
+
+    def __init__(self, *args, **kwds):
+        self.args = args
+        self.kwds = kwds
+
+    def run(self):
+        fn, = self.fn
+        fn(*self.args, **self.kwds)
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        self.parent = greenlet.getcurrent()
+        result = self.switch()
+        if self:
+            return result
+        else:
+            raise StopIteration
+
+    # Hack: Python < 2.6 compatibility
+    next = __next__
+
+
+def Yield(value):
+    g = greenlet.getcurrent()
+    while not isinstance(g, genlet):
+        if g is None:
+            raise RuntimeError('yield outside a genlet')
+        g = g.parent
+    g.parent.switch(value)
+
+
+def generator(func):
+    class generator(genlet):
+        fn = (func,)
+    return generator
+
+# ____________________________________________________________
+
+
+class GeneratorTests(unittest.TestCase):
+    def test_generator(self):
+        seen = []
+
+        def g(n):
+            for i in range(n):
+                seen.append(i)
+                Yield(i)
+        g = generator(g)
+        for k in range(3):
+            for j in g(5):
+                seen.append(j)
+        self.assertEqual(seen, 3 * [0, 0, 1, 1, 2, 2, 3, 3, 4, 4])
diff --git a/src/greenlet/tests/test_generator_nested.py b/src/greenlet/tests/test_generator_nested.py
new file mode 100644
index 0000000..6b4f023
--- /dev/null
+++ b/src/greenlet/tests/test_generator_nested.py
@@ -0,0 +1,165 @@
+import unittest
+from greenlet import greenlet
+
+
+class genlet(greenlet):
+
+    def __init__(self, *args, **kwds):
+        self.args = args
+        self.kwds = kwds
+        self.child = None
+
+    def run(self):
+        fn, = self.fn
+        fn(*self.args, **self.kwds)
+
+    def __iter__(self):
+        return self
+
+    def set_child(self, child):
+        self.child = child
+
+    def __next__(self):
+        if self.child:
+            child = self.child
+            while child.child:
+                tmp = child
+                child = child.child
+                tmp.child = None
+
+            result = child.switch()
+        else:
+            self.parent = greenlet.getcurrent()
+            result = self.switch()
+
+        if self:
+            return result
+        else:
+            raise StopIteration
+
+    # Hack: Python < 2.6 compatibility
+    next = __next__
+
+
+def Yield(value, level=1):
+    g = greenlet.getcurrent()
+
+    while level != 0:
+        if not isinstance(g, genlet):
+            raise RuntimeError('yield outside a genlet')
+        if level > 1:
+            g.parent.set_child(g)
+        g = g.parent
+        level -= 1
+
+    g.switch(value)
+
+
+def Genlet(func):
+    class Genlet(genlet):
+        fn = (func,)
+    return Genlet
+
+# ____________________________________________________________
+
+
+def g1(n, seen):
+    for i in range(n):
+        seen.append(i + 1)
+        yield i
+
+
+def g2(n, seen):
+    for i in range(n):
+        seen.append(i + 1)
+        Yield(i)
+
+g2 = Genlet(g2)
+
+
+def nested(i):
+    Yield(i)
+
+
+def g3(n, seen):
+    for i in range(n):
+        seen.append(i + 1)
+        nested(i)
+g3 = Genlet(g3)
+
+
+def a(n):
+    if n == 0:
+        return
+    for ii in ax(n - 1):
+        Yield(ii)
+    Yield(n)
+ax = Genlet(a)
+
+
+def perms(l):
+    if len(l) > 1:
+        for e in l:
+            # No syntactical sugar for generator expressions
+            [Yield([e] + p) for p in perms([x for x in l if x != e])]
+    else:
+        Yield(l)
+perms = Genlet(perms)
+
+
+def gr1(n):
+    for ii in range(1, n):
+        Yield(ii)
+        Yield(ii * ii, 2)
+
+gr1 = Genlet(gr1)
+
+
+def gr2(n, seen):
+    for ii in gr1(n):
+        seen.append(ii)
+
+gr2 = Genlet(gr2)
+
+
+class NestedGeneratorTests(unittest.TestCase):
+    def test_layered_genlets(self):
+        seen = []
+        for ii in gr2(5, seen):
+            seen.append(ii)
+        self.assertEqual(seen, [1, 1, 2, 4, 3, 9, 4, 16])
+
+    def test_permutations(self):
+        gen_perms = perms(list(range(4)))
+        permutations = list(gen_perms)
+        self.assertEqual(len(permutations), 4 * 3 * 2 * 1)
+        self.assertTrue([0, 1, 2, 3] in permutations)
+        self.assertTrue([3, 2, 1, 0] in permutations)
+        res = []
+        for ii in zip(perms(list(range(4))), perms(list(range(3)))):
+            res.append(ii)
+        self.assertEqual(
+            res,
+            [([0, 1, 2, 3], [0, 1, 2]), ([0, 1, 3, 2], [0, 2, 1]),
+             ([0, 2, 1, 3], [1, 0, 2]), ([0, 2, 3, 1], [1, 2, 0]),
+             ([0, 3, 1, 2], [2, 0, 1]), ([0, 3, 2, 1], [2, 1, 0])])
+        # XXX Test to make sure we are working as a generator expression
+
+    def test_genlet_simple(self):
+        for g in [g1, g2, g3]:
+            seen = []
+            for k in range(3):
+                for j in g(5, seen):
+                    seen.append(j)
+            self.assertEqual(seen, 3 * [1, 0, 2, 1, 3, 2, 4, 3, 5, 4])
+
+    def test_genlet_bad(self):
+        try:
+            Yield(10)
+        except RuntimeError:
+            pass
+
+    def test_nested_genlets(self):
+        seen = []
+        for ii in ax(5):
+            seen.append(ii)
diff --git a/src/greenlet/tests/test_greenlet.py b/src/greenlet/tests/test_greenlet.py
new file mode 100644
index 0000000..5a3fe10
--- /dev/null
+++ b/src/greenlet/tests/test_greenlet.py
@@ -0,0 +1,542 @@
+import gc
+import sys
+import time
+import threading
+import unittest
+
+from greenlet import greenlet
+
+try:
+    from abc import ABCMeta, abstractmethod
+except ImportError:
+    ABCMeta = None
+    abstractmethod = None
+
+
+class SomeError(Exception):
+    pass
+
+
+def fmain(seen):
+    try:
+        greenlet.getcurrent().parent.switch()
+    except:
+        seen.append(sys.exc_info()[0])
+        raise
+    raise SomeError
+
+
+def send_exception(g, exc):
+    # note: send_exception(g, exc)  can be now done with  g.throw(exc).
+    # the purpose of this test is to explicitely check the propagation rules.
+    def crasher(exc):
+        raise exc
+    g1 = greenlet(crasher, parent=g)
+    g1.switch(exc)
+
+
+class GreenletTests(unittest.TestCase):
+    def test_simple(self):
+        lst = []
+
+        def f():
+            lst.append(1)
+            greenlet.getcurrent().parent.switch()
+            lst.append(3)
+        g = greenlet(f)
+        lst.append(0)
+        g.switch()
+        lst.append(2)
+        g.switch()
+        lst.append(4)
+        self.assertEqual(lst, list(range(5)))
+
+    def test_parent_equals_None(self):
+        g = greenlet(parent=None)
+
+    def test_run_equals_None(self):
+        g = greenlet(run=None)
+
+    def test_two_children(self):
+        lst = []
+
+        def f():
+            lst.append(1)
+            greenlet.getcurrent().parent.switch()
+            lst.extend([1, 1])
+        g = greenlet(f)
+        h = greenlet(f)
+        g.switch()
+        self.assertEqual(len(lst), 1)
+        h.switch()
+        self.assertEqual(len(lst), 2)
+        h.switch()
+        self.assertEqual(len(lst), 4)
+        self.assertEqual(h.dead, True)
+        g.switch()
+        self.assertEqual(len(lst), 6)
+        self.assertEqual(g.dead, True)
+
+    def test_two_recursive_children(self):
+        lst = []
+
+        def f():
+            lst.append(1)
+            greenlet.getcurrent().parent.switch()
+
+        def g():
+            lst.append(1)
+            g = greenlet(f)
+            g.switch()
+            lst.append(1)
+        g = greenlet(g)
+        g.switch()
+        self.assertEqual(len(lst), 3)
+        self.assertEqual(sys.getrefcount(g), 2)
+
+    def test_threads(self):
+        success = []
+
+        def f():
+            self.test_simple()
+            success.append(True)
+        ths = [threading.Thread(target=f) for i in range(10)]
+        for th in ths:
+            th.start()
+        for th in ths:
+            th.join()
+        self.assertEqual(len(success), len(ths))
+
+    def test_exception(self):
+        seen = []
+        g1 = greenlet(fmain)
+        g2 = greenlet(fmain)
+        g1.switch(seen)
+        g2.switch(seen)
+        g2.parent = g1
+        self.assertEqual(seen, [])
+        self.assertRaises(SomeError, g2.switch)
+        self.assertEqual(seen, [SomeError])
+        g2.switch()
+        self.assertEqual(seen, [SomeError])
+
+    def test_send_exception(self):
+        seen = []
+        g1 = greenlet(fmain)
+        g1.switch(seen)
+        self.assertRaises(KeyError, send_exception, g1, KeyError)
+        self.assertEqual(seen, [KeyError])
+
+    def test_dealloc(self):
+        seen = []
+        g1 = greenlet(fmain)
+        g2 = greenlet(fmain)
+        g1.switch(seen)
+        g2.switch(seen)
+        self.assertEqual(seen, [])
+        del g1
+        gc.collect()
+        self.assertEqual(seen, [greenlet.GreenletExit])
+        del g2
+        gc.collect()
+        self.assertEqual(seen, [greenlet.GreenletExit, greenlet.GreenletExit])
+
+    def test_dealloc_other_thread(self):
+        seen = []
+        someref = []
+        lock = threading.Lock()
+        lock.acquire()
+        lock2 = threading.Lock()
+        lock2.acquire()
+
+        def f():
+            g1 = greenlet(fmain)
+            g1.switch(seen)
+            someref.append(g1)
+            del g1
+            gc.collect()
+            lock.release()
+            lock2.acquire()
+            greenlet()   # trigger release
+            lock.release()
+            lock2.acquire()
+        t = threading.Thread(target=f)
+        t.start()
+        lock.acquire()
+        self.assertEqual(seen, [])
+        self.assertEqual(len(someref), 1)
+        del someref[:]
+        gc.collect()
+        # g1 is not released immediately because it's from another thread
+        self.assertEqual(seen, [])
+        lock2.release()
+        lock.acquire()
+        self.assertEqual(seen, [greenlet.GreenletExit])
+        lock2.release()
+        t.join()
+
+    def test_frame(self):
+        def f1():
+            f = sys._getframe(0)
+            self.assertEqual(f.f_back, None)
+            greenlet.getcurrent().parent.switch(f)
+            return "meaning of life"
+        g = greenlet(f1)
+        frame = g.switch()
+        self.assertTrue(frame is g.gr_frame)
+        self.assertTrue(g)
+        next = g.switch()
+        self.assertFalse(g)
+        self.assertEqual(next, 'meaning of life')
+        self.assertEqual(g.gr_frame, None)
+
+    def test_thread_bug(self):
+        def runner(x):
+            g = greenlet(lambda: time.sleep(x))
+            g.switch()
+        t1 = threading.Thread(target=runner, args=(0.2,))
+        t2 = threading.Thread(target=runner, args=(0.3,))
+        t1.start()
+        t2.start()
+        t1.join()
+        t2.join()
+
+    def test_switch_kwargs(self):
+        def foo(a, b):
+            self.assertEqual(a, 4)
+            self.assertEqual(b, 2)
+        greenlet(foo).switch(a=4, b=2)
+
+    def test_switch_kwargs_to_parent(self):
+        def foo(x):
+            greenlet.getcurrent().parent.switch(x=x)
+            greenlet.getcurrent().parent.switch(2, x=3)
+            return x, x ** 2
+        g = greenlet(foo)
+        self.assertEqual({'x': 3}, g.switch(3))
+        self.assertEqual(((2,), {'x': 3}), g.switch())
+        self.assertEqual((3, 9), g.switch())
+
+    def test_switch_to_another_thread(self):
+        data = {}
+        error = None
+        created_event = threading.Event()
+        done_event = threading.Event()
+
+        def foo():
+            data['g'] = greenlet(lambda: None)
+            created_event.set()
+            done_event.wait()
+        thread = threading.Thread(target=foo)
+        thread.start()
+        created_event.wait()
+        try:
+            data['g'].switch()
+        except greenlet.error:
+            error = sys.exc_info()[1]
+        self.assertTrue(error != None, "greenlet.error was not raised!")
+        done_event.set()
+        thread.join()
+
+    def test_exc_state(self):
+        def f():
+            try:
+                raise ValueError('fun')
+            except:
+                exc_info = sys.exc_info()
+                greenlet(h).switch()
+                self.assertEqual(exc_info, sys.exc_info())
+
+        def h():
+            self.assertEqual(sys.exc_info(), (None, None, None))
+
+        greenlet(f).switch()
+
+    def test_instance_dict(self):
+        def f():
+            greenlet.getcurrent().test = 42
+        def deldict(g):
+            del g.__dict__
+        def setdict(g, value):
+            g.__dict__ = value
+        g = greenlet(f)
+        self.assertEqual(g.__dict__, {})
+        g.switch()
+        self.assertEqual(g.test, 42)
+        self.assertEqual(g.__dict__, {'test': 42})
+        g.__dict__ = g.__dict__
+        self.assertEqual(g.__dict__, {'test': 42})
+        self.assertRaises(TypeError, deldict, g)
+        self.assertRaises(TypeError, setdict, g, 42)
+
+    def test_threaded_reparent(self):
+        data = {}
+        created_event = threading.Event()
+        done_event = threading.Event()
+
+        def foo():
+            data['g'] = greenlet(lambda: None)
+            created_event.set()
+            done_event.wait()
+
+        def blank():
+            greenlet.getcurrent().parent.switch()
+
+        def setparent(g, value):
+            g.parent = value
+
+        thread = threading.Thread(target=foo)
+        thread.start()
+        created_event.wait()
+        g = greenlet(blank)
+        g.switch()
+        self.assertRaises(ValueError, setparent, g, data['g'])
+        done_event.set()
+        thread.join()
+
+    def test_deepcopy(self):
+        import copy
+        self.assertRaises(TypeError, copy.copy, greenlet())
+        self.assertRaises(TypeError, copy.deepcopy, greenlet())
+
+    def test_parent_restored_on_kill(self):
+        hub = greenlet(lambda: None)
+        main = greenlet.getcurrent()
+        result = []
+        def worker():
+            try:
+                # Wait to be killed
+                main.switch()
+            except greenlet.GreenletExit:
+                # Resurrect and switch to parent
+                result.append(greenlet.getcurrent().parent)
+                result.append(greenlet.getcurrent())
+                hub.switch()
+        g = greenlet(worker, parent=hub)
+        g.switch()
+        del g
+        self.assertTrue(result)
+        self.assertEqual(result[0], main)
+        self.assertEqual(result[1].parent, hub)
+
+    def test_parent_return_failure(self):
+        # No run causes AttributeError on switch
+        g1 = greenlet()
+        # Greenlet that implicitly switches to parent
+        g2 = greenlet(lambda: None, parent=g1)
+        # AttributeError should propagate to us, no fatal errors
+        self.assertRaises(AttributeError, g2.switch)
+
+    def test_throw_exception_not_lost(self):
+        class mygreenlet(greenlet):
+            def __getattribute__(self, name):
+                try:
+                    raise Exception()
+                except:
+                    pass
+                return greenlet.__getattribute__(self, name)
+        g = mygreenlet(lambda: None)
+        self.assertRaises(SomeError, g.throw, SomeError())
+
+    def test_throw_doesnt_crash(self):
+        result = []
+        def worker():
+            greenlet.getcurrent().parent.switch()
+        def creator():
+            g = greenlet(worker)
+            g.switch()
+            result.append(g)
+        t = threading.Thread(target=creator)
+        t.start()
+        t.join()
+        self.assertRaises(greenlet.error, result[0].throw, SomeError())
+
+    def test_recursive_startup(self):
+        class convoluted(greenlet):
+            def __init__(self):
+                greenlet.__init__(self)
+                self.count = 0
+            def __getattribute__(self, name):
+                if name == 'run' and self.count == 0:
+                    self.count = 1
+                    self.switch(43)
+                return greenlet.__getattribute__(self, name)
+            def run(self, value):
+                while True:
+                    self.parent.switch(value)
+        g = convoluted()
+        self.assertEqual(g.switch(42), 43)
+
+    def test_unexpected_reparenting(self):
+        another = []
+        def worker():
+            g = greenlet(lambda: None)
+            another.append(g)
+            g.switch()
+        t = threading.Thread(target=worker)
+        t.start()
+        t.join()
+        class convoluted(greenlet):
+            def __getattribute__(self, name):
+                if name == 'run':
+                    self.parent = another[0]
+                return greenlet.__getattribute__(self, name)
+        g = convoluted(lambda: None)
+        self.assertRaises(greenlet.error, g.switch)
+
+    def test_threaded_updatecurrent(self):
+        # released when main thread should execute
+        lock1 = threading.Lock()
+        lock1.acquire()
+        # released when another thread should execute
+        lock2 = threading.Lock()
+        lock2.acquire()
+        class finalized(object):
+            def __del__(self):
+                # happens while in green_updatecurrent() in main greenlet
+                # should be very careful not to accidentally call it again
+                # at the same time we must make sure another thread executes
+                lock2.release()
+                lock1.acquire()
+                # now ts_current belongs to another thread
+        def deallocator():
+            greenlet.getcurrent().parent.switch()
+        def fthread():
+            lock2.acquire()
+            greenlet.getcurrent()
+            del g[0]
+            lock1.release()
+            lock2.acquire()
+            greenlet.getcurrent()
+            lock1.release()
+        main = greenlet.getcurrent()
+        g = [greenlet(deallocator)]
+        g[0].bomb = finalized()
+        g[0].switch()
+        t = threading.Thread(target=fthread)
+        t.start()
+        # let another thread grab ts_current and deallocate g[0]
+        lock2.release()
+        lock1.acquire()
+        # this is the corner stone
+        # getcurrent() will notice that ts_current belongs to another thread
+        # and start the update process, which would notice that g[0] should
+        # be deallocated, and that will execute an object's finalizer. Now,
+        # that object will let another thread run so it can grab ts_current
+        # again, which would likely crash the interpreter if there's no
+        # check for this case at the end of green_updatecurrent(). This test
+        # passes if getcurrent() returns correct result, but it's likely
+        # to randomly crash if it's not anyway.
+        self.assertEqual(greenlet.getcurrent(), main)
+        # wait for another thread to complete, just in case
+        t.join()
+
+    def test_dealloc_switch_args_not_lost(self):
+        seen = []
+        def worker():
+            # wait for the value
+            value = greenlet.getcurrent().parent.switch()
+            # delete all references to ourself
+            del worker[0]
+            initiator.parent = greenlet.getcurrent().parent
+            # switch to main with the value, but because
+            # ts_current is the last reference to us we
+            # return immediately
+            try:
+                greenlet.getcurrent().parent.switch(value)
+            finally:
+                seen.append(greenlet.getcurrent())
+        def initiator():
+            return 42 # implicitly falls thru to parent
+        worker = [greenlet(worker)]
+        worker[0].switch() # prime worker
+        initiator = greenlet(initiator, worker[0])
+        value = initiator.switch()
+        self.assertTrue(seen)
+        self.assertEqual(value, 42)
+
+    if sys.version_info[0] == 2:
+        # There's no apply in Python 3.x
+        def test_tuple_subclass(self):
+            class mytuple(tuple):
+                def __len__(self):
+                    greenlet.getcurrent().switch()
+                    return tuple.__len__(self)
+            args = mytuple()
+            kwargs = dict(a=42)
+            def switchapply():
+                apply(greenlet.getcurrent().parent.switch, args, kwargs)
+            g = greenlet(switchapply)
+            self.assertEqual(g.switch(), kwargs)
+
+    if ABCMeta is not None and abstractmethod is not None:
+        def test_abstract_subclasses(self):
+            AbstractSubclass = ABCMeta(
+                'AbstractSubclass',
+                (greenlet,),
+                {'run': abstractmethod(lambda self: None)})
+
+            class BadSubclass(AbstractSubclass):
+                pass
+
+            class GoodSubclass(AbstractSubclass):
+                def run(self):
+                    pass
+
+            GoodSubclass() # should not raise
+            self.assertRaises(TypeError, BadSubclass)
+
+    def test_implicit_parent_with_threads(self):
+        if not gc.isenabled():
+            return # cannot test with disabled gc
+        N = gc.get_threshold()[0]
+        if N < 50:
+            return # cannot test with such a small N
+        def attempt():
+            lock1 = threading.Lock()
+            lock1.acquire()
+            lock2 = threading.Lock()
+            lock2.acquire()
+            recycled = [False]
+            def another_thread():
+                lock1.acquire() # wait for gc
+                greenlet.getcurrent() # update ts_current
+                lock2.release() # release gc
+            t = threading.Thread(target=another_thread)
+            t.start()
+            class gc_callback(object):
+                def __del__(self):
+                    lock1.release()
+                    lock2.acquire()
+                    recycled[0] = True
+            class garbage(object):
+                def __init__(self):
+                    self.cycle = self
+                    self.callback = gc_callback()
+            l = []
+            x = range(N*2)
+            current = greenlet.getcurrent()
+            g = garbage()
+            for i in x:
+                g = None # lose reference to garbage
+                if recycled[0]:
+                    # gc callback called prematurely
+                    t.join()
+                    return False
+                last = greenlet()
+                if recycled[0]:
+                    break # yes! gc called in green_new
+                l.append(last) # increase allocation counter
+            else:
+                # gc callback not called when expected
+                gc.collect()
+                if recycled[0]:
+                    t.join()
+                return False
+            self.assertEqual(last.parent, current)
+            for g in l:
+                self.assertEqual(g.parent, current)
+            return True
+        for i in range(5):
+            if attempt():
+                break
diff --git a/src/greenlet/tests/test_leaks.py b/src/greenlet/tests/test_leaks.py
new file mode 100644
index 0000000..2b24ea0
--- /dev/null
+++ b/src/greenlet/tests/test_leaks.py
@@ -0,0 +1,85 @@
+import unittest
+import sys
+import gc
+
+import time
+import weakref
+import greenlet
+import threading
+
+
+class ArgRefcountTests(unittest.TestCase):
+    def test_arg_refs(self):
+        args = ('a', 'b', 'c')
+        refcount_before = sys.getrefcount(args)
+        g = greenlet.greenlet(
+            lambda *args: greenlet.getcurrent().parent.switch(*args))
+        for i in range(100):
+            g.switch(*args)
+        self.assertEqual(sys.getrefcount(args), refcount_before)
+
+    def test_kwarg_refs(self):
+        kwargs = {}
+        g = greenlet.greenlet(
+            lambda **kwargs: greenlet.getcurrent().parent.switch(**kwargs))
+        for i in range(100):
+            g.switch(**kwargs)
+        self.assertEqual(sys.getrefcount(kwargs), 2)
+
+    if greenlet.GREENLET_USE_GC:
+        # These only work with greenlet gc support
+
+        def recycle_threads(self):
+            # By introducing a thread that does sleep we allow other threads,
+            # that have triggered their __block condition, but did not have a
+            # chance to deallocate their thread state yet, to finally do so.
+            # The way it works is by requiring a GIL switch (different thread),
+            # which does a GIL release (sleep), which might do a GIL switch
+            # to finished threads and allow them to clean up.
+            def worker():
+                time.sleep(0.001)
+            t = threading.Thread(target=worker)
+            t.start()
+            time.sleep(0.001)
+            t.join()
+
+        def test_threaded_leak(self):
+            gg = []
+            def worker():
+                # only main greenlet present
+                gg.append(weakref.ref(greenlet.getcurrent()))
+            for i in range(2):
+                t = threading.Thread(target=worker)
+                t.start()
+                t.join()
+                del t
+            greenlet.getcurrent() # update ts_current
+            self.recycle_threads()
+            greenlet.getcurrent() # update ts_current
+            gc.collect()
+            greenlet.getcurrent() # update ts_current
+            for g in gg:
+                self.assertTrue(g() is None)
+
+        def test_threaded_adv_leak(self):
+            gg = []
+            def worker():
+                # main and additional *finished* greenlets
+                ll = greenlet.getcurrent().ll = []
+                def additional():
+                    ll.append(greenlet.getcurrent())
+                for i in range(2):
+                    greenlet.greenlet(additional).switch()
+                gg.append(weakref.ref(greenlet.getcurrent()))
+            for i in range(2):
+                t = threading.Thread(target=worker)
+                t.start()
+                t.join()
+                del t
+            greenlet.getcurrent() # update ts_current
+            self.recycle_threads()
+            greenlet.getcurrent() # update ts_current
+            gc.collect()
+            greenlet.getcurrent() # update ts_current
+            for g in gg:
+                self.assertTrue(g() is None)
diff --git a/src/greenlet/tests/test_stack_saved.py b/src/greenlet/tests/test_stack_saved.py
new file mode 100644
index 0000000..6c7353b
--- /dev/null
+++ b/src/greenlet/tests/test_stack_saved.py
@@ -0,0 +1,19 @@
+import greenlet
+import unittest
+
+
+class Test(unittest.TestCase):
+
+    def test_stack_saved(self):
+        main = greenlet.getcurrent()
+        self.assertEqual(main._stack_saved, 0)
+
+        def func():
+            main.switch(main._stack_saved)
+
+        g = greenlet.greenlet(func)
+        x = g.switch()
+        assert x > 0, x
+        assert g._stack_saved > 0, g._stack_saved
+        g.switch()
+        assert g._stack_saved == 0, g._stack_saved
diff --git a/src/greenlet/tests/test_throw.py b/src/greenlet/tests/test_throw.py
new file mode 100644
index 0000000..a2014a9
--- /dev/null
+++ b/src/greenlet/tests/test_throw.py
@@ -0,0 +1,100 @@
+import sys
+import unittest
+
+from greenlet import greenlet
+
+
+def switch(*args):
+    return greenlet.getcurrent().parent.switch(*args)
+
+
+class ThrowTests(unittest.TestCase):
+    def test_class(self):
+        def f():
+            try:
+                switch("ok")
+            except RuntimeError:
+                switch("ok")
+                return
+            switch("fail")
+        g = greenlet(f)
+        res = g.switch()
+        self.assertEqual(res, "ok")
+        res = g.throw(RuntimeError)
+        self.assertEqual(res, "ok")
+
+    def test_val(self):
+        def f():
+            try:
+                switch("ok")
+            except RuntimeError:
+                val = sys.exc_info()[1]
+                if str(val) == "ciao":
+                    switch("ok")
+                    return
+            switch("fail")
+
+        g = greenlet(f)
+        res = g.switch()
+        self.assertEqual(res, "ok")
+        res = g.throw(RuntimeError("ciao"))
+        self.assertEqual(res, "ok")
+
+        g = greenlet(f)
+        res = g.switch()
+        self.assertEqual(res, "ok")
+        res = g.throw(RuntimeError, "ciao")
+        self.assertEqual(res, "ok")
+
+    def test_kill(self):
+        def f():
+            switch("ok")
+            switch("fail")
+        g = greenlet(f)
+        res = g.switch()
+        self.assertEqual(res, "ok")
+        res = g.throw()
+        self.assertTrue(isinstance(res, greenlet.GreenletExit))
+        self.assertTrue(g.dead)
+        res = g.throw()    # immediately eaten by the already-dead greenlet
+        self.assertTrue(isinstance(res, greenlet.GreenletExit))
+
+    def test_throw_goes_to_original_parent(self):
+        main = greenlet.getcurrent()
+
+        def f1():
+            try:
+                main.switch("f1 ready to catch")
+            except IndexError:
+                return "caught"
+            else:
+                return "normal exit"
+
+        def f2():
+            main.switch("from f2")
+
+        g1 = greenlet(f1)
+        g2 = greenlet(f2, parent=g1)
+        self.assertRaises(IndexError, g2.throw, IndexError)
+        self.assertTrue(g2.dead)
+        self.assertTrue(g1.dead)
+
+        g1 = greenlet(f1)
+        g2 = greenlet(f2, parent=g1)
+        res = g1.switch()
+        self.assertEqual(res, "f1 ready to catch")
+        res = g2.throw(IndexError)
+        self.assertEqual(res, "caught")
+        self.assertTrue(g2.dead)
+        self.assertTrue(g1.dead)
+
+        g1 = greenlet(f1)
+        g2 = greenlet(f2, parent=g1)
+        res = g1.switch()
+        self.assertEqual(res, "f1 ready to catch")
+        res = g2.switch()
+        self.assertEqual(res, "from f2")
+        res = g2.throw(IndexError)
+        self.assertEqual(res, "caught")
+        self.assertTrue(g2.dead)
+        self.assertTrue(g1.dead)
diff --git a/src/greenlet/tests/test_tracing.py b/src/greenlet/tests/test_tracing.py
new file mode 100644
index 0000000..4f34b15
--- /dev/null
+++ b/src/greenlet/tests/test_tracing.py
@@ -0,0 +1,52 @@
+import unittest
+import threading
+import greenlet
+
+class SomeError(Exception):
+    pass
+
+class TracingTests(unittest.TestCase):
+    if greenlet.GREENLET_USE_TRACING:
+        def test_greenlet_tracing(self):
+            main = greenlet.getcurrent()
+            actions = []
+            def trace(*args):
+                actions.append(args)
+            def dummy():
+                pass
+            def dummyexc():
+                raise SomeError()
+            oldtrace = greenlet.settrace(trace)
+            try:
+                g1 = greenlet.greenlet(dummy)
+                g1.switch()
+                g2 = greenlet.greenlet(dummyexc)
+                self.assertRaises(SomeError, g2.switch)
+            finally:
+                greenlet.settrace(oldtrace)
+            self.assertEqual(actions, [
+                ('switch', (main, g1)),
+                ('switch', (g1, main)),
+                ('switch', (main, g2)),
+                ('throw', (g2, main)),
+            ])
+
+        def test_exception_disables_tracing(self):
+            main = greenlet.getcurrent()
+            actions = []
+            def trace(*args):
+                actions.append(args)
+                raise SomeError()
+            def dummy():
+                main.switch()
+            g = greenlet.greenlet(dummy)
+            g.switch()
+            oldtrace = greenlet.settrace(trace)
+            try:
+                self.assertRaises(SomeError, g.switch)
+                self.assertEqual(greenlet.gettrace(), None)
+            finally:
+                greenlet.settrace(oldtrace)
+            self.assertEqual(actions, [
+                ('switch', (main, g)),
+            ])
diff --git a/src/greenlet/tests/test_version.py b/src/greenlet/tests/test_version.py
new file mode 100755
index 0000000..f4ea056
--- /dev/null
+++ b/src/greenlet/tests/test_version.py
@@ -0,0 +1,49 @@
+#! /usr/bin/env python
+from __future__ import absolute_import
+from __future__ import print_function
+
+import sys
+import os
+import re
+import unittest
+
+import greenlet
+
+class VersionTests(unittest.TestCase):
+    def test_version(self):
+        def find_dominating_file(name):
+            here = os.path.abspath(os.path.dirname(__file__))
+            for i in range(10):
+                up = ['..'] * i
+                path = [here] + up + [name]
+                fname = os.path.join(*path)
+                fname = os.path.abspath(fname)
+                if os.path.exists(fname):
+                    return fname
+            raise AssertionError("Could not find file " + name + "; last checked " + fname)
+
+        try:
+            setup_py = find_dominating_file('setup.py')
+        except AssertionError as e:
+            raise unittest.SkipTest("Unable to find setup.py; must be out of tree. " + str(e))
+
+        try:
+            greenlet_h = find_dominating_file('greenlet.h')
+        except AssertionError as e:
+            if '.tox' in os.path.abspath(os.path.dirname(__file__)):
+                raise unittest.SkipTest("Unable to find greenlet.h while running in tox")
+            raise
+
+        with open(greenlet_h) as f:
+            greenlet_h = f.read()
+
+        hversion, = re.findall('GREENLET_VERSION "(.*)"', greenlet_h)
+
+
+
+        invoke_setup = "%s %s --version" % (sys.executable, setup_py)
+        with os.popen(invoke_setup) as f:
+            sversion = f.read().strip()
+
+        self.assertEqual(sversion, hversion)
+        self.assertEqual(sversion, greenlet.__version__)
diff --git a/src/greenlet/tests/test_weakref.py b/src/greenlet/tests/test_weakref.py
new file mode 100644
index 0000000..6a2ff06
--- /dev/null
+++ b/src/greenlet/tests/test_weakref.py
@@ -0,0 +1,34 @@
+import gc
+import greenlet
+import weakref
+import unittest
+
+
+class WeakRefTests(unittest.TestCase):
+    def test_dead_weakref(self):
+        def _dead_greenlet():
+            g = greenlet.greenlet(lambda: None)
+            g.switch()
+            return g
+        o = weakref.ref(_dead_greenlet())
+        gc.collect()
+        self.assertEqual(o(), None)
+
+    def test_inactive_weakref(self):
+        o = weakref.ref(greenlet.greenlet())
+        gc.collect()
+        self.assertEqual(o(), None)
+
+    def test_dealloc_weakref(self):
+        seen = []
+        def worker():
+            try:
+                greenlet.getcurrent().parent.switch()
+            finally:
+                seen.append(g())
+        g = greenlet.greenlet(worker)
+        g.switch()
+        g2 = greenlet.greenlet(lambda: None, g)
+        g = weakref.ref(g2)
+        g2 = None
+        self.assertEqual(seen, [None])