C++ify xmethod_worker, get rid of VEC(xmethod_worker_ptr)

The initial goal of this patch was to remove the usage of
VEC(xmethod_worker_ptr) and corresponding cleanups.  I ended up having
to  C++ify the xmethod_worker code, to be able to have xmethod_workers
free their data in destructors, and therefore be able to use vectors of
xmethod_worker unique_ptr.

The operations in extension_language_ops that act on one instance of
xmethod_worker (get result type, get args type, invoke) are transformed
to methods of xmethod_worker.  xmethod_worker becomes an abstract base
class with virtual pure methods which python_xmethod_worker implements.
The only xmethod-related operation left in extension_language_ops is
get_matching_xmethod_workers, which returns a list of xmethod_workers.

The changes are relatively straightforward, but here are some notes on
things that may raise eyebrows:

  - I was not really comfortable with the value_of_xmethod function.  At
  first it looks like a simple getter, so I considered making it a
  method of xmethod_worker.  But actually it creates a value and
  transfers the ownership of the xmethod_worker to it.  It would be a
  bit weird and error-prone if calling a method on an object silently
  removed the ownership of the object from the caller.  To reflect the
  behavior more accurately, I renamed it to value_from_xmethod and made
  it accept an rvalue-reference (so the caller knows it gives away the
  ownership).  I noticed the backlink from xmethod_worker to its owning
  value was not used, so I removed it.

  - Some code, like get_matching_xmethod_workers, made each callee fill
  a new vector, which was then merged in the result vector.  I think
  it's safe if we always pass the same vector around, and each
  implementation just appends to it.

  - The clone operation does not seem particularly useful, it is removed
  in the following patch.

gdb/ChangeLog:

	* extension-priv.h (enum ext_lang_rc): Remove, move to extension.h.
	(struct extension_language_ops) <clone_xmethod_worker_data>: Remove.
	<free_xmethod_worker_data>: Remove.
	<get_matching_xmethod_workers>: Chance VEC to std::vector.
	<get_xmethod_arg_types>: Remove.
	<get_xmethod_result_type>: Remove.
	<invoke_xmethod>: Remove.
	* extension.c (new_xmethod_worker): Remove.
	(clone_xmethod_worker): Remove.
	(get_matching_xmethod_workers): Return void, pass std::vector by
	pointer.
	(get_xmethod_arg_types): Rename to...
	(xmethod_worker::get_arg_types): ... this, and adjust.
	(get_xmethod_result_type): Rename to...
	(xmethod_worker::get_result_type): ... this, and adjust.
	(invoke_xmethod): Remove.
	(free_xmethod_worker): Remove.
	(free_xmethod_worker_vec): Remove.
	* extension.h (enum ext_lang_rc): Move here from
	extension-priv.h.
	(struct xmethod_worker): Add constructor and destructor.
	<data>: Remove.
	<value>: Remove.
	<invoke, clone, do_get_result_type, do_get_arg_types>: New
	virtual pure methods.
	<get_arg_types, get_result_type>: New methods.
	(xmethod_worker_ptr): Remove typedef.
	(DEF_VEC_P (xmethod_worker_ptr)): Remove.
	(xmethod_worker_vec): Remove typedef.
	(xmethod_worker_up): New typedef.
	(invoke_xmethod): Remove.
	(clone_xmethod_worker): Remove.
	(free_xmethod_worker): Remove.
	(free_xmethod_worker_vec): Remove.
	(get_xmethod_arg_types): Remove.
	(get_xmethod_result_type): Remove.
	* valops.c (find_method_list): Use std::vector, don't use
	intermediate vector.
	(value_find_oload_method_list): Use std::vector.
	(find_overload_match): Use std::vector.
	(find_oload_champ): Use std::vector.
	* value.c (value_free): Use operator delete.
	(value_of_xmethod): Rename to...
	(value_from_xmethod): ... this.  Don't assign
	xmethod_worker::value, take rvalue-reference.
	(result_type_of_xmethod): Adjust.
	(call_xmethod): Adjust.
	* value.h: Include extension.h.
	(struct xmethod_worker): Don't forward-declare.
	(value_of_xmethod): Rename to...
	(value_from_xmethod): ... this, take rvalue-reference.
	* python/py-xmethods.c (struct gdbpy_worker_data): Rename to...
	(struct python_xmethod_worker): ... this, add constructor and
	destructor.
	<invoke, clone, do_get_arg_types, do_get_result_type>: Implement.
	(gdbpy_free_xmethod_worker_data): Rename to...
	(python_xmethod_worker::~python_xmethod_worker): ... this and
	adjust.
	(gdbpy_clone_xmethod_worker_data): Rename to...
	(python_xmethod_worker::clone): ... this and adjust.
	(gdbpy_get_matching_xmethod_workers): Use std::vector, don't use
	temporary vector.
	(gdbpy_get_xmethod_arg_types): Rename to...
	(python_xmethod_worker::do_get_arg_types): ... this and adjust.
	(gdbpy_get_xmethod_result_type): Rename to...
	(python_xmethod_worker::do_get_result_type): ... this and
	adjust.
	(gdbpy_invoke_xmethod): Rename to...
	(python_xmethod_worker::invoke): ... this and adjust.
	(new_python_xmethod_worker): Rename to...
	(python_xmethod_worker::python_xmethod_worker): ... this and
	adjust.
	* python/python-internal.h (gdbpy_clone_xmethod_worker_data):
	Remove.
	(gdbpy_free_xmethod_worker_data): Remove.
	(gdbpy_get_matching_xmethod_workers): Use std::vector.
	(gdbpy_get_xmethod_arg_types): Remove.
	(gdbpy_get_xmethod_result_type): Remove.
	(gdbpy_invoke_xmethod): Remove.
	* python/python.c (python_extension_ops): Remove obsolete
	callbacks.

1 files changed, 5 insertions, 70 deletions

diff --git a/gdb/extension-priv.h b/gdb/extension-priv.h
index 8fbf1b0c769..5843479f93c 100644
--- a/gdb/extension-priv.h
+++ b/gdb/extension-priv.h
@@ -25,26 +25,6 @@
 #include <signal.h>
 #include "cli/cli-script.h"
 
-/* The return code for some API calls.  */
-
-enum ext_lang_rc
-  {
-    /* The operation completed successfully.  */
-    EXT_LANG_RC_OK,
-
-    /* The operation was not performed (e.g., no pretty-printer).  */
-    EXT_LANG_RC_NOP,
-
-    /* There was an error (e.g., Python error while printing a value).
-       When an error occurs no further extension languages are tried.
-       This is to preserve existing behaviour, and because it's convenient
-       for Python developers.
-       Note: This is different than encountering a memory error trying to read
-       a value for pretty-printing.  Here we're referring to, e.g., programming
-       errors that trigger an exception in the extension language.  */
-    EXT_LANG_RC_ERROR
-  };
-
 /* High level description of an extension/scripting language.
    An entry for each is compiled into GDB regardless of whether the support
    is present.  This is done so that we can issue meaningful errors if the
@@ -261,63 +241,18 @@ struct extension_language_ops
   enum ext_lang_rc (*before_prompt) (const struct extension_language_defn *,
 				     const char *current_gdb_prompt);
 
-  /* xmethod support:
-     clone_xmethod_worker_data, free_xmethod_worker_data,
-     get_matching_xmethod_workers, get_xmethod_arg_types,
-     get_xmethod_return_type, invoke_xmethod.
-     These methods are optional and may be NULL, but if one of them is
-     implemented then they all must be.  */
-
-  /* Clone DATA and return a new but identical xmethod worker data
-     object for this extension language.  */
-  void * (*clone_xmethod_worker_data)
-    (const struct extension_language_defn *extlang, void *data);
-
-  /* Free the DATA object of this extension language.  */
-  void (*free_xmethod_worker_data)
-    (const struct extension_language_defn *extlang, void *data);
-
   /* Return a vector of matching xmethod workers defined in this
      extension language.  The workers service methods with name
      METHOD_NAME on objects of type OBJ_TYPE.  The vector is returned
-     in DM_VEC.  */
+     in DM_VEC.
+
+     This field may be NULL if the extension language does not support
+     xmethods.  */
   enum ext_lang_rc (*get_matching_xmethod_workers)
     (const struct extension_language_defn *extlang,
      struct type *obj_type,
      const char *method_name,
-     xmethod_worker_vec **dm_vec);
-
-  /* Given a WORKER servicing a particular method, return the types
-     of the arguments the method takes.  The number of arguments is
-     returned in NARGS, and their types are returned in the array
-     ARGTYPES.  */
-  enum ext_lang_rc (*get_xmethod_arg_types)
-    (const struct extension_language_defn *extlang,
-     struct xmethod_worker *worker,
-     int *nargs,
-     struct type ***arg_types);
-
-  /* Given a WORKER servicing a particular method, fetch the type of the
-     result of the method.  OBJECT, ARGS, NARGS are the same as for
-     invoke_xmethod.  The result type is stored in *RESULT_TYPE.
-     For backward compatibility with 7.9, which did not support getting the
-     result type, if the get_result_type operation is not provided by WORKER
-     then EXT_LANG_RC_OK is returned and NULL is returned in *RESULT_TYPE.  */
-  enum ext_lang_rc (*get_xmethod_result_type)
-    (const struct extension_language_defn *extlang,
-     struct xmethod_worker *worker,
-     struct value *object, struct value **args, int nargs,
-     struct type **result_type);
-
-  /* Invoke the xmethod serviced by WORKER.  The xmethod is invoked
-     on OBJECT with arguments in the array ARGS.  NARGS is the length of
-     this array.  Returns the value returned by the xmethod.  */
-  struct value * (*invoke_xmethod)
-    (const struct extension_language_defn *extlang,
-     struct xmethod_worker *worker,
-     struct value *object,
-     struct value **args,
-     int nargs);
+     std::vector<xmethod_worker_up> *dm_vec);
 };
 
 /* State necessary to restore a signal handler to its previous value.  */