gh-122931: Allow stable abi3 API extensions to include a multiarch tuple in the filename (GH-152461)

This permits stable ABI extensions for multiple architectures to be
co-installed into the same directory, without clashing with each other,
the same way (non-stable ABI) regular extensions can.

It is listed before the current platform-less suffixes since it's more
specific.

The platform is stored in a new pyconfig.h define & sysconfig
variable, SOABI_PLATFORM.
On some known architectures (FreeBSD, Windows), this
will be undefined/zero; these won't have the new tag (yet).

Add SOABI_PLATFORM & ALT_SOABI the info to
`make pythoninfo` as well.

Co-authored-by: Petr Viktorin <encukou@gmail.com>
Co-authored-by: Victor Stinner <vstinner@python.org>

Doc/whatsnew/3.15.rst

@@ -873,6 +873,14 @@ Other language changes
   imports ``pkg.sub.mod``.
   (Contributed by Gregory P. Smith in :gh:`83065`.)
 
+* File names of Stable ABI extensions that use the ``.so`` suffix may now
+  include a multiarch tuple, for example, ``foo.abi3-x86-64-linux-gnu.so``.
+  This permits stable ABI extensions for multiple architectures to be
+  co-installed into the same directory, without clashing with each
+  other, as regular dynamic extensions do.
+  (Contributed by Stefano Rivera in :gh:`122931`.)
+
+
 
 Default interactive shell
 =========================

Lib/test/pythoninfo.py

@@ -570,6 +570,7 @@ def collect_sysconfig(info_add):
 
     for name in (
         'ABIFLAGS',
+        'ALT_SOABI',
         'ANDROID_API_LEVEL',
         'CC',
         'CCSHARED',
@@ -595,6 +596,7 @@ def collect_sysconfig(info_add):
         'Py_REMOTE_DEBUG',
         'SHELL',
         'SOABI',
+        'SOABI_PLATFORM',
         'TEST_MODULES',
         'VAPTH',
         'abs_builddir',
@@ -1315,6 +1317,12 @@ def collect_system(info_add):
             info_add('system.hardware', hardware)
 
 
+def collect_importlib(info_add):
+    import importlib.machinery
+    info_add('importlib.extension_suffixes',
+             importlib.machinery.EXTENSION_SUFFIXES)
+
+
 def collect_info(info):
     error = False
     info_add = info.add
@@ -1357,6 +1365,7 @@ def collect_info(info):
         collect_zstd,
         collect_libregrtest_utils,
         collect_system,
+        collect_importlib,
 
         # Collecting from tests should be last as they have side effects.
         collect_test_socket,

Lib/test/test_importlib/extension/test_finder.py

@@ -5,6 +5,7 @@ machinery = util.import_importlib('importlib.machinery')
 
 import unittest
 import sys
+import sysconfig
 
 
 class FinderTests(abc.FinderTests):
@@ -61,6 +62,7 @@ class FinderTests(abc.FinderTests):
 
     def test_abi3_extension_suffixes(self):
         suffixes = self.machinery.EXTENSION_SUFFIXES
+        platform = sysconfig.get_config_var("SOABI_PLATFORM")
         if 'win32' in sys.platform:
             # Either "_d.pyd" or ".pyd" must be in suffixes
             self.assertTrue({"_d.pyd", ".pyd"}.intersection(suffixes))
@@ -73,6 +75,13 @@ class FinderTests(abc.FinderTests):
                 self.assertIn(".abi3.so", suffixes)
             self.assertIn(".abi3t.so", suffixes)
 
+            if platform:
+                if Py_GIL_DISABLED:
+                    self.assertNotIn(f".abi3-{platform}.so", suffixes)
+                else:
+                    self.assertIn(f".abi3-{platform}.so", suffixes)
+                self.assertIn(f".abi3t-{platform}.so", suffixes)
+
 
 (Frozen_FinderTests,
  Source_FinderTests

Lib/test/test_sysconfig.py

@@ -457,6 +457,15 @@ class TestSysConfig(unittest.TestCase, VirtualEnvironmentMixin):
         soabi = sysconfig.get_config_var('SOABI')
         self.assertIn(soabi, _imp.extension_suffixes()[0])
 
+    @unittest.skipIf(not _imp.extension_suffixes(), "stub loader has no suffixes")
+    @unittest.skipIf(sys.platform == "win32", "Does not apply to Windows")
+    @unittest.skipIf(sysconfig.get_config_var('SOABI_PLATFORM') == 0,
+                     "SOABI_PLATFORM is undefined")
+    def test_soabi_platform(self):
+        soabi_platform = sysconfig.get_config_var('SOABI_PLATFORM')
+        soabi = sysconfig.get_config_var('SOABI')
+        self.assertIn(soabi_platform, soabi)
+
     def test_library(self):
         library = sysconfig.get_config_var('LIBRARY')
         ldlibrary = sysconfig.get_config_var('LDLIBRARY')

Misc/NEWS.d/next/C_API/2024-08-12-09-48-04.gh-issue-122931.x435Mb.rst

@@ -0,0 +1 @@
+Allow importing stable ABI C extensions that include a multiarch tuple in their filename, e.g. ``foo.abi3-x86-64-linux-gnu.so``.

Python/dynload_shlib.c

@@ -46,8 +46,14 @@ const char *_PyImport_DynLoadFiletab[] = {
     "." ALT_SOABI ".so",
 #endif
 #ifndef Py_GIL_DISABLED
+#ifdef SOABI_PLATFORM
+    ".abi" PYTHON_ABI_STRING "-" SOABI_PLATFORM ".so",
+#endif  /* SOABI_PLATFORM */
     ".abi" PYTHON_ABI_STRING ".so",
 #endif  /* Py_GIL_DISABLED */
+#ifdef SOABI_PLATFORM
+    ".abi" PYTHON_ABI_STRING "t-" SOABI_PLATFORM ".so",
+#endif  /* SOABI_PLATFORM */
     ".abi" PYTHON_ABI_STRING "t.so",
     ".so",
 #endif  /* __CYGWIN__ */

configure

@@ -7395,6 +7395,12 @@ case $ac_sys_system in #(
  ;;
 esac
 
+if test x$SOABI_PLATFORM != x; then
+
+printf "%s\n" "#define SOABI_PLATFORM \"${SOABI_PLATFORM}\"" >>confdefs.h
+
+fi
+
 if test x$MULTIARCH != x; then
   MULTIARCH_CPPFLAGS="-DMULTIARCH=\\\"$MULTIARCH\\\""
 fi

configure.ac

@@ -1221,6 +1221,10 @@ AS_CASE([$ac_sys_system],
   [SOABI_PLATFORM=$PLATFORM_TRIPLET]
 )
 
+if test x$SOABI_PLATFORM != x; then
+    AC_DEFINE_UNQUOTED([SOABI_PLATFORM], ["${SOABI_PLATFORM}"], [Platform tag, used in binary module extension filenames.])
+fi
+
 if test x$MULTIARCH != x; then
   MULTIARCH_CPPFLAGS="-DMULTIARCH=\\\"$MULTIARCH\\\""
 fi

pyconfig.h.in

@@ -1968,6 +1968,9 @@
 /* The size of '_Bool', as computed by sizeof. */
 #undef SIZEOF__BOOL
 
+/* Platform tag, used in binary module extension filenames. */
+#undef SOABI_PLATFORM
+
 /* Define to 1 if you have the ANSI C header files. */
 #undef STDC_HEADERS