bpo-45847: Port _posixshmem to PY_STDLIB_MOD (GH-29738)

Modules/Setup.stdlib.in

@@ -122,6 +122,9 @@
 @MODULE_SYSLOG_TRUE@syslog syslogmodule.c
 @MODULE_TERMIOS_TRUE@termios termios.c
 
+# multiprocessing
+@MODULE__POSIXSHMEM_TRUE@_posixshmem _multiprocessing/posixshmem.c
+
 
 ############################################################################
 # Modules with third party dependencies

configure

@@ -710,6 +710,8 @@ MODULE_OSSAUDIODEV_FALSE
 MODULE_OSSAUDIODEV_TRUE
 MODULE_GRP_FALSE
 MODULE_GRP_TRUE
+MODULE__POSIXSHMEM_FALSE
+MODULE__POSIXSHMEM_TRUE
 MODULE_MMAP_FALSE
 MODULE_MMAP_TRUE
 MODULE_FCNTL_FALSE
@@ -20030,8 +20032,13 @@ fi
 
 # checks for POSIX shared memory, used by Modules/_multiprocessing/posixshmem.c
 # shm_* may only be available if linking against librt
-save_LIBS="$LIBS"
-save_includes_default="$ac_includes_default"
+POSIXSHMEM_CFLAGS='-I$(srcdir)/Modules/_multiprocessing'
+save_CFLAGS=$CFLAGS
+save_CPPFLAGS=$CPPFLAGS
+save_LDFLAGS=$LDFLAGS
+save_LIBS=$LIBS
+
+
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing shm_open" >&5
 $as_echo_n "checking for library containing shm_open... " >&6; }
 if ${ac_cv_search_shm_open+:} false; then :
@@ -20088,24 +20095,11 @@ if test "$ac_res" != no; then :
 
 fi
 
-if test "$ac_cv_search_shm_open" = "-lrt"; then
-
-$as_echo "#define SHM_NEEDS_LIBRT 1" >>confdefs.h
-
-fi
-for ac_header in sys/mman.h
-do :
-  ac_fn_c_check_header_mongrel "$LINENO" "sys/mman.h" "ac_cv_header_sys_mman_h" "$ac_includes_default"
-if test "x$ac_cv_header_sys_mman_h" = xyes; then :
-  cat >>confdefs.h <<_ACEOF
-#define HAVE_SYS_MMAN_H 1
-_ACEOF
-
+  if test "x$ac_cv_search_shm_open" = x-lrt; then :
+  POSIXSHMEM_LIBS="-lrt"
 fi
 
-done
-
-# temporarily override ac_includes_default for AC_CHECK_FUNCS below
+    save_ac_includes_default=$ac_includes_default
   ac_includes_default="\
   ${ac_includes_default}
   #ifndef __cplusplus
@@ -20122,13 +20116,20 @@ if eval test \"x\$"$as_ac_var"\" = x"yes"; then :
   cat >>confdefs.h <<_ACEOF
 #define `$as_echo "HAVE_$ac_func" | $as_tr_cpp` 1
 _ACEOF
-
+ have_posix_shmem=yes
+else
+  have_posix_shmem=no
 fi
 done
 
-# we don't want to link with librt always, restore LIBS
-LIBS="$save_LIBS"
-ac_includes_default="$save_includes_default"
+  ac_includes_default=$save_ac_includes_default
+
+CFLAGS=$save_CFLAGS
+CPPFLAGS=$save_CPPFLAGS
+LDFLAGS=$save_LDFLAGS
+LIBS=$save_LIBS
+
+
 
 # Check for usable OpenSSL
 
@@ -21072,6 +21073,42 @@ fi
 $as_echo "$py_cv_module_mmap" >&6; }
 
 
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for stdlib extension module _posixshmem" >&5
+$as_echo_n "checking for stdlib extension module _posixshmem... " >&6; }
+      case $py_stdlib_not_available in #(
+  *_posixshmem*) :
+    py_cv_module__posixshmem=n/a ;; #(
+  *) :
+    if true; then :
+  if test "$have_posix_shmem" = "yes"; then :
+  py_cv_module__posixshmem=yes
+else
+  py_cv_module__posixshmem=missing
+fi
+else
+  py_cv_module__posixshmem=disabled
+fi
+   ;;
+esac
+  as_fn_append MODULE_BLOCK "MODULE__POSIXSHMEM=$py_cv_module__posixshmem$as_nl"
+  if test "x$py_cv_module__posixshmem" = xyes; then :
+
+    as_fn_append MODULE_BLOCK "MODULE__POSIXSHMEM_CFLAGS=$POSIXSHMEM_CFLAGS$as_nl"
+    as_fn_append MODULE_BLOCK "MODULE__POSIXSHMEM_LDFLAGS=$POSIXSHMEM_LIBS$as_nl"
+
+fi
+   if test "$py_cv_module__posixshmem" = yes; then
+  MODULE__POSIXSHMEM_TRUE=
+  MODULE__POSIXSHMEM_FALSE='#'
+else
+  MODULE__POSIXSHMEM_TRUE='#'
+  MODULE__POSIXSHMEM_FALSE=
+fi
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $py_cv_module__posixshmem" >&5
+$as_echo "$py_cv_module__posixshmem" >&6; }
+
+
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for stdlib extension module grp" >&5
 $as_echo_n "checking for stdlib extension module grp... " >&6; }
@@ -22621,6 +22658,10 @@ if test -z "${MODULE_MMAP_TRUE}" && test -z "${MODULE_MMAP_FALSE}"; then
   as_fn_error $? "conditional \"MODULE_MMAP\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
+if test -z "${MODULE__POSIXSHMEM_TRUE}" && test -z "${MODULE__POSIXSHMEM_FALSE}"; then
+  as_fn_error $? "conditional \"MODULE__POSIXSHMEM\" was never defined.
+Usually this means the macro was only invoked conditionally." "$LINENO" 5
+fi
 if test -z "${MODULE_GRP_TRUE}" && test -z "${MODULE_GRP_FALSE}"; then
   as_fn_error $? "conditional \"MODULE_GRP\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5

configure.ac

@@ -5875,15 +5875,13 @@ AS_VAR_IF([ac_cv_func_getrandom], [yes], [
 
 # checks for POSIX shared memory, used by Modules/_multiprocessing/posixshmem.c
 # shm_* may only be available if linking against librt
-save_LIBS="$LIBS"
-save_includes_default="$ac_includes_default"
-AC_SEARCH_LIBS(shm_open, rt)
-if test "$ac_cv_search_shm_open" = "-lrt"; then
-    AC_DEFINE(SHM_NEEDS_LIBRT, 1,
-              [Define to 1 if you must link with -lrt for shm_open().])
-fi
-AC_CHECK_HEADERS(sys/mman.h)
-# temporarily override ac_includes_default for AC_CHECK_FUNCS below
+POSIXSHMEM_CFLAGS='-I$(srcdir)/Modules/_multiprocessing'
+WITH_SAVE_ENV([
+  AC_SEARCH_LIBS([shm_open], [rt])
+  AS_VAR_IF([ac_cv_search_shm_open], [-lrt], [POSIXSHMEM_LIBS="-lrt"])
+
+  dnl Temporarily override ac_includes_default for AC_CHECK_FUNCS below.
+  _SAVE_VAR([ac_includes_default])
   ac_includes_default="\
   ${ac_includes_default}
   #ifndef __cplusplus
@@ -5892,10 +5890,9 @@ ${ac_includes_default}
   #  endif
   #endif
   "
-AC_CHECK_FUNCS([shm_open shm_unlink])
-# we don't want to link with librt always, restore LIBS
-LIBS="$save_LIBS"
-ac_includes_default="$save_includes_default"
+  AC_CHECK_FUNCS([shm_open shm_unlink], [have_posix_shmem=yes], [have_posix_shmem=no])
+  _RESTORE_VAR([ac_includes_default])
+])
 
 # Check for usable OpenSSL
 AX_CHECK_OPENSSL([have_openssl=yes],[have_openssl=no])
@@ -6251,6 +6248,9 @@ PY_STDLIB_MOD([fcntl],
   [], [$FCNTL_LIBS])
 PY_STDLIB_MOD([mmap],
   [], [test "$ac_cv_header_sys_mman_h" = "yes" -a "$ac_cv_header_sys_stat_h" = "yes"])
+PY_STDLIB_MOD([_posixshmem],
+  [], [test "$have_posix_shmem" = "yes"],
+  [$POSIXSHMEM_CFLAGS], [$POSIXSHMEM_LIBS])
 
 dnl platform specific extensions
 PY_STDLIB_MOD([grp], [], [test "$ac_cv_func_getgrgid" = yes -o "$ac_cv_func_getgrgid_r" = yes])

pyconfig.h.in

@@ -1469,9 +1469,6 @@
 /* Define if setpgrp() must be called as setpgrp(0, 0). */
 #undef SETPGRP_HAVE_ARG
 
-/* Define to 1 if you must link with -lrt for shm_open(). */
-#undef SHM_NEEDS_LIBRT
-
 /* Define if i>>j for signed int i does not extend the sign bit when i < 0 */
 #undef SIGNED_RIGHT_SHIFT_ZERO_FILLS
 

setup.py

@@ -1397,20 +1397,7 @@ class PyBuildExt(build_ext):
         self.add(Extension('_multiprocessing', multiprocessing_srcs,
                            include_dirs=["Modules/_multiprocessing"]))
 
-        if (not MS_WINDOWS and
-           sysconfig.get_config_var('HAVE_SHM_OPEN') and
-           sysconfig.get_config_var('HAVE_SHM_UNLINK')):
-            posixshmem_srcs = ['_multiprocessing/posixshmem.c']
-            libs = []
-            if sysconfig.get_config_var('SHM_NEEDS_LIBRT'):
-                # need to link with librt to get shm_open()
-                libs.append('rt')
-            self.add(Extension('_posixshmem', posixshmem_srcs,
-                               define_macros={},
-                               libraries=libs,
-                               include_dirs=["Modules/_multiprocessing"]))
-        else:
-            self.missing.append('_posixshmem')
+        self.addext(Extension('_posixshmem', ['_multiprocessing/posixshmem.c']))
 
     def detect_uuid(self):
         # Build the _uuid module if possible