gh-101758: Clean Up Uses of Import State (gh-101919)

This change is almost entirely moving code around and hiding import state behind internal API.  We introduce no changes to behavior, nor to non-internal API.  (Since there was already going to be a lot of churn, I took this as an opportunity to re-organize import.c into topically-grouped sections of code.)  The motivation is to simplify a number of upcoming changes.

Specific changes:

* move existing import-related code to import.c, wherever possible
* add internal API for interacting with import state (both global and per-interpreter)
* use only API outside of import.c (to limit churn there when changing the location, etc.)
* consolidate the import-related state of PyInterpreterState into a single struct field (this changes layout slightly)
* add macros for import state in import.c (to simplify changing the location)
* group code in import.c into sections
*remove _PyState_AddModule()

https://github.com/python/cpython/issues/101758

1 files changed, 7 insertions, 10 deletions

diff --git a/Python/importdl.c b/Python/importdl.c
index 91fa06f49c..6dafb45414 100644
--- a/Python/importdl.c
+++ b/Python/importdl.c
@@ -99,7 +99,7 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
 #endif
     PyObject *name_unicode = NULL, *name = NULL, *path = NULL, *m = NULL;
     const char *name_buf, *hook_prefix;
-    const char *oldcontext;
+    const char *oldcontext, *newcontext;
     dl_funcptr exportfunc;
     PyModuleDef *def;
     PyModInitFunction p0;
@@ -113,6 +113,10 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
                         "spec.name must be a string");
         goto error;
     }
+    newcontext = PyUnicode_AsUTF8(name_unicode);
+    if (newcontext == NULL) {
+        goto error;
+    }
 
     name = get_encoded_name(name_unicode, &hook_prefix);
     if (name == NULL) {
@@ -160,16 +164,9 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
     p0 = (PyModInitFunction)exportfunc;
 
     /* Package context is needed for single-phase init */
-#define _Py_PackageContext (_PyRuntime.imports.pkgcontext)
-    oldcontext = _Py_PackageContext;
-    _Py_PackageContext = PyUnicode_AsUTF8(name_unicode);
-    if (_Py_PackageContext == NULL) {
-        _Py_PackageContext = oldcontext;
-        goto error;
-    }
+    oldcontext = _PyImport_SwapPackageContext(newcontext);
     m = _PyImport_InitFunc_TrampolineCall(p0);
-    _Py_PackageContext = oldcontext;
-#undef _Py_PackageContext
+    _PyImport_SwapPackageContext(oldcontext);
 
     if (m == NULL) {
         if (!PyErr_Occurred()) {