[gcc r13-8006] libstdc++: use -D_GNU_SOURCE when building libbacktrace

[gcc r13-8006] libstdc++: use -D_GNU_SOURCE when building libbacktrace

[Ian Lance Taylor]

https://gcc.gnu.org/g:8484e3479fe80aebdc4a2406473aef906055b4f8

commit r13-8006-g8484e3479fe80aebdc4a2406473aef906055b4f8
Author: Ian Lance Taylor <iant@golang.org>
Date:   Mon Nov 6 15:12:05 2023 -0800

    libstdc++: use -D_GNU_SOURCE when building libbacktrace
    
            PR libbacktrace/111315
            PR libbacktrace/112263
            * acinclude.m4: Set -D_GNU_SOURCE in BACKTRACE_CPPFLAGS and when
            grepping link.h for dl_iterate_phdr.
            * configure: Regenerate.

Diff:
---
 libstdc++-v3/acinclude.m4 | 5 ++++-
 libstdc++-v3/configure    | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 49cb0623e4f..ad533d478aa 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -4977,7 +4977,7 @@ AC_DEFUN([GLIBCXX_ENABLE_BACKTRACE], [
 
   # Most of this is adapted from libsanitizer/configure.ac
 
-  BACKTRACE_CPPFLAGS=
+  BACKTRACE_CPPFLAGS="-D_GNU_SOURCE"
 
   # libbacktrace only needs atomics for int, which we've already tested
   if test "$glibcxx_cv_atomic_int" = "yes"; then
@@ -5005,8 +5005,11 @@ AC_DEFUN([GLIBCXX_ENABLE_BACKTRACE], [
     have_dl_iterate_phdr=no
   else
     # When built as a GCC target library, we can't do a link test.
+    ac_save_CPPFLAGS="$CPPFLAGS"
+    CPPFLAGS="$CPPFLAGS -D_GNU_SOURCE"
     AC_EGREP_HEADER([dl_iterate_phdr], [link.h], [have_dl_iterate_phdr=yes],
 		    [have_dl_iterate_phdr=no])
+    CPPFLAGS="$ac_save_CPPFLAGS"
   fi
   if test "$have_dl_iterate_phdr" = "yes"; then
     BACKTRACE_CPPFLAGS="$BACKTRACE_CPPFLAGS -DHAVE_DL_ITERATE_PHDR=1"
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 9b602777545..65d7e8c7f91 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -71067,7 +71067,7 @@ fi
 
   # Most of this is adapted from libsanitizer/configure.ac
 
-  BACKTRACE_CPPFLAGS=
+  BACKTRACE_CPPFLAGS="-D_GNU_SOURCE"
 
   # libbacktrace only needs atomics for int, which we've already tested
   if test "$glibcxx_cv_atomic_int" = "yes"; then
@@ -71150,6 +71150,8 @@ done
     have_dl_iterate_phdr=no
   else
     # When built as a GCC target library, we can't do a link test.
+    ac_save_CPPFLAGS="$CPPFLAGS"
+    CPPFLAGS="$CPPFLAGS -D_GNU_SOURCE"
     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 #include <link.h>
@@ -71163,6 +71165,7 @@ else
 fi
 rm -f conftest*
 
+    CPPFLAGS="$ac_save_CPPFLAGS"
   fi
   if test "$have_dl_iterate_phdr" = "yes"; then
     BACKTRACE_CPPFLAGS="$BACKTRACE_CPPFLAGS -DHAVE_DL_ITERATE_PHDR=1"