bpo-38980: Only apply -fno-semantic-interposition if available

aclocal.m4

@@ -12,6 +12,60 @@
 # PARTICULAR PURPOSE.
 
 m4_ifndef([AC_CONFIG_MACRO_DIRS], [m4_defun([_AM_CONFIG_MACRO_DIRS], [])m4_defun([AC_CONFIG_MACRO_DIRS], [_AM_CONFIG_MACRO_DIRS($@)])])
+# ===========================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CHECK_COMPILE_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT])
+#
+# DESCRIPTION
+#
+#   Check whether the given FLAG works with the current language's compiler
+#   or gives an error.  (Warnings, however, are ignored)
+#
+#   ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on
+#   success/failure.
+#
+#   If EXTRA-FLAGS is defined, it is added to the current language's default
+#   flags (e.g. CFLAGS) when the check is done.  The check is thus made with
+#   the flags: "CFLAGS EXTRA-FLAGS FLAG".  This can for example be used to
+#   force the compiler to issue an error when a bad flag is given.
+#
+#   INPUT gives an alternative input source to AC_COMPILE_IFELSE.
+#
+#   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
+#   macro in sync with AX_CHECK_{PREPROC,LINK}_FLAG.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#   Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+#serial 6
+
+AC_DEFUN([AX_CHECK_COMPILE_FLAG],
+[AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
+AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl
+AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [
+  ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS
+  _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1"
+  AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
+    [AS_VAR_SET(CACHEVAR,[yes])],
+    [AS_VAR_SET(CACHEVAR,[no])])
+  _AC_LANG_PREFIX[]FLAGS=$ax_check_save_flags])
+AS_VAR_IF(CACHEVAR,yes,
+  [m4_default([$2], :)],
+  [m4_default([$3], :)])
+AS_VAR_POPDEF([CACHEVAR])dnl
+])dnl AX_CHECK_COMPILE_FLAGS
+
 # pkg.m4 - Macros to locate and utilise pkg-config.   -*- Autoconf -*-
 # serial 11 (pkg-config-0.29.1)
 

configure

@@ -6484,8 +6484,44 @@ if test "$Py_OPT" = 'true' ; then
   DEF_MAKE_RULE="build_all"
   case $CC in
     *gcc*)
+      { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether C compiler accepts -fno-semantic-interposition" >&5
+$as_echo_n "checking whether C compiler accepts -fno-semantic-interposition... " >&6; }
+if ${ax_cv_check_cflags___fno_semantic_interposition+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+  ax_check_save_flags=$CFLAGS
+  CFLAGS="$CFLAGS  -fno-semantic-interposition"
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ax_cv_check_cflags___fno_semantic_interposition=yes
+else
+  ax_cv_check_cflags___fno_semantic_interposition=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+  CFLAGS=$ax_check_save_flags
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_check_cflags___fno_semantic_interposition" >&5
+$as_echo "$ax_cv_check_cflags___fno_semantic_interposition" >&6; }
+if test "x$ax_cv_check_cflags___fno_semantic_interposition" = xyes; then :
+
       CFLAGS_NODIST="$CFLAGS_NODIST -fno-semantic-interposition"
       LDFLAGS_NODIST="$LDFLAGS_NODIST -fno-semantic-interposition"
+
+else
+  :
+fi
+
       ;;
   esac
 

configure.ac

@@ -1320,8 +1320,10 @@ if test "$Py_OPT" = 'true' ; then
   DEF_MAKE_RULE="build_all"
   case $CC in
     *gcc*)
+      AX_CHECK_COMPILE_FLAG([-fno-semantic-interposition],[
       CFLAGS_NODIST="$CFLAGS_NODIST -fno-semantic-interposition"
       LDFLAGS_NODIST="$LDFLAGS_NODIST -fno-semantic-interposition"
+      ])
       ;;
   esac