gh-122907: Fix Builds Without HAVE_DYNAMIC_LOADING Set (gh-122952)

As of 529a160 (gh-118204), building with HAVE_DYNAMIC_LOADING stopped working.  This is a minimal fix just to get builds working again.  There are actually a number of long-standing deficiencies with HAVE_DYNAMIC_LOADING builds that need to be resolved separately.

Include/internal/pycore_importdl.h

@@ -56,9 +56,11 @@ extern int _Py_ext_module_loader_info_init_for_core(
 extern int _Py_ext_module_loader_info_init_for_builtin(
     struct _Py_ext_module_loader_info *p_info,
     PyObject *name);
+#ifdef HAVE_DYNAMIC_LOADING
 extern int _Py_ext_module_loader_info_init_from_spec(
     struct _Py_ext_module_loader_info *info,
     PyObject *spec);
+#endif
 
 /* The result from running an extension module's init function. */
 struct _Py_ext_module_loader_result {
@@ -87,9 +89,11 @@ extern void _Py_ext_module_loader_result_apply_error(
 
 /* The module init function. */
 typedef PyObject *(*PyModInitFunction)(void);
+#ifdef HAVE_DYNAMIC_LOADING
 extern PyModInitFunction _PyImport_GetModInitFunc(
     struct _Py_ext_module_loader_info *info,
     FILE *fp);
+#endif
 extern int _PyImport_RunModInitFunc(
     PyModInitFunction p0,
     struct _Py_ext_module_loader_info *info,

Lib/importlib/_bootstrap_external.py

@@ -1523,13 +1523,13 @@ def _get_supported_file_loaders():
 
     Each item is a tuple (loader, suffixes).
     """
+    extension_loaders = []
+    if hasattr(_imp, 'create_dynamic'):
         if sys.platform in {"ios", "tvos", "watchos"}:
             extension_loaders = [(AppleFrameworkLoader, [
                 suffix.replace(".so", ".fwork")
                 for suffix in _imp.extension_suffixes()
             ])]
-    else:
-        extension_loaders = []
         extension_loaders.append((ExtensionFileLoader, _imp.extension_suffixes()))
     source = SourceFileLoader, SOURCE_SUFFIXES
     bytecode = SourcelessFileLoader, BYTECODE_SUFFIXES

Misc/NEWS.d/next/Core_and_Builtins/2024-08-12-11-19-37.gh-issue-122907.q68096.rst

@@ -0,0 +1,3 @@
+Building with ``HAVE_DYNAMIC_LOADING`` now works as well as it did in 3.12.
+Existing deficiences will be addressed separately.
+(See https://github.com/python/cpython/issues/122950.)

Python/importdl.c

@@ -8,6 +8,8 @@
 #include "pycore_pystate.h"
 #include "pycore_runtime.h"
 
+#include "pycore_importdl.h"
+
 /* ./configure sets HAVE_DYNAMIC_LOADING if dynamic loading of modules is
    supported on this platform. configure will then compile and link in one
    of the dynload_*.c files, as appropriate. We will call a function in
@@ -15,8 +17,6 @@
 */
 #ifdef HAVE_DYNAMIC_LOADING
 
-#include "pycore_importdl.h"
-
 #ifdef MS_WINDOWS
 extern dl_funcptr _PyImport_FindSharedFuncptrWindows(const char *prefix,
                                                      const char *shortname,
@@ -28,6 +28,8 @@ extern dl_funcptr _PyImport_FindSharedFuncptr(const char *prefix,
                                               const char *pathname, FILE *fp);
 #endif
 
+#endif /* HAVE_DYNAMIC_LOADING */
+
 
 /***********************************/
 /* module info to use when loading */
@@ -205,6 +207,7 @@ _Py_ext_module_loader_info_init_for_core(
     return 0;
 }
 
+#ifdef HAVE_DYNAMIC_LOADING
 int
 _Py_ext_module_loader_info_init_from_spec(
                             struct _Py_ext_module_loader_info *p_info,
@@ -226,6 +229,7 @@ _Py_ext_module_loader_info_init_from_spec(
     Py_DECREF(filename);
     return err;
 }
+#endif /* HAVE_DYNAMIC_LOADING */
 
 
 /********************************/
@@ -372,6 +376,7 @@ _Py_ext_module_loader_result_apply_error(
 /* getting/running the module init function */
 /********************************************/
 
+#ifdef HAVE_DYNAMIC_LOADING
 PyModInitFunction
 _PyImport_GetModInitFunc(struct _Py_ext_module_loader_info *info,
                          FILE *fp)
@@ -406,6 +411,7 @@ _PyImport_GetModInitFunc(struct _Py_ext_module_loader_info *info,
 
     return (PyModInitFunction)exportfunc;
 }
+#endif /* HAVE_DYNAMIC_LOADING */
 
 int
 _PyImport_RunModInitFunc(PyModInitFunction p0,
@@ -513,5 +519,3 @@ error:
     p_res->err = &p_res->_err;
     return -1;
 }
-
-#endif /* HAVE_DYNAMIC_LOADING */

Tools/build/check_extension_modules.py

@@ -27,6 +27,7 @@ import re
 import sys
 import sysconfig
 import warnings
+import _imp
 
 from importlib._bootstrap import _load as bootstrap_load
 from importlib.machinery import BuiltinImporter, ExtensionFileLoader, ModuleSpec
@@ -153,6 +154,11 @@ class ModuleChecker:
         self.notavailable = []
 
     def check(self):
+        if not hasattr(_imp, 'create_dynamic'):
+            logger.warning(
+                ('Dynamic extensions not supported '
+                 '(HAVE_DYNAMIC_LOADING not defined)'),
+            )
         for modinfo in self.modules:
             logger.debug("Checking '%s' (%s)", modinfo.name, self.get_location(modinfo))
             if modinfo.state == ModuleState.DISABLED:
@@ -414,6 +420,9 @@ class ModuleChecker:
             logger.error("%s failed to import: %s", modinfo.name, e)
             raise
         except Exception as e:
+            if not hasattr(_imp, 'create_dynamic'):
+                logger.warning("Dynamic extension '%s' ignored", modinfo.name)
+                return
             logger.exception("Importing extension '%s' failed!", modinfo.name)
             raise