[committed] libstdc++: Remove use of undefined GLIBCXX_LANG_{PUSH, POP} [PR120147]

[Jonathan Wakely]

Commit r16-427-g86627faec10da5 was using the new GLIBCXX_LANG_PUSH and
GLIBCXX_LANG_POP macros from a change that I haven't pushed yet,
resulting in changes to CXXFLAGS not being restored after the
GLIBCXX_ENABLE_BACKTRACE checks.

libstdc++-v3/ChangeLog:

        PR libstdc++/120147
        * acinclude.m4 (GLIBCXX_ENABLE_BACKTRACE): Restore use of
        AC_LANG_CPLUSPLUS.
        * configure: Regenerate.
---

Lightly tested x86_64-linux and x86_64-w64-mingw. Pushed to trunk.

 libstdc++-v3/acinclude.m4 |  6 ++++--
 libstdc++-v3/configure    | 20 ++++++++++++++++----
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 0fc74d00a98..204bed5b27b 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -5290,7 +5290,8 @@ AC_DEFUN([GLIBCXX_ENABLE_BACKTRACE], [
 
   BACKTRACE_CPPFLAGS="-D_GNU_SOURCE"
 
-  GLIBCXX_LANG_PUSH
+  AC_LANG_CPLUSPLUS
+  old_CXXFLAGS="$CXXFLAGS"
 
   # libbacktrace's own configure.ac only tests atomics for int,
   # but the code actually uses atomics for size_t and pointers as well.
@@ -5356,7 +5357,8 @@ EOF
     rm -f conftest*
   fi
 
-  GLIBCXX_LANG_POP
+  CXXFLAGS="$old_CXXFLAGS"
+  AC_LANG_RESTORE
 
   if test "$glibcxx_cv_libbacktrace_atomics" = yes; then
     BACKTRACE_CPPFLAGS="$BACKTRACE_CPPFLAGS -DHAVE_ATOMIC_FUNCTIONS=1"
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 3fd03b8a95d..0529ff5708f 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -53537,7 +53537,13 @@ fi
 
   BACKTRACE_CPPFLAGS="-D_GNU_SOURCE"
 
-  GLIBCXX_LANG_PUSH
+  ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS 
conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+  old_CXXFLAGS="$CXXFLAGS"
 
   # libbacktrace's own configure.ac only tests atomics for int,
   # but the code actually uses atomics for size_t and pointers as well.
@@ -53578,7 +53584,7 @@ main ()
   return 0;
 }
 _ACEOF
-if ac_fn_c_try_link "$LINENO"; then :
+if ac_fn_cxx_try_link "$LINENO"; then :
   glibcxx_cv_libbacktrace_atomics=yes
 else
   glibcxx_cv_libbacktrace_atomics=no
@@ -53595,7 +53601,7 @@ $as_echo "$glibcxx_cv_libbacktrace_atomics" >&6; }
     CXXFLAGS='-O0 -S'
 
     cat > conftest.$ac_ext << EOF
-#line 53598 "configure"
+#line 53604 "configure"
 #include <stddef.h>
 int main()
 {
@@ -53633,7 +53639,13 @@ $as_echo "$glibcxx_cv_libbacktrace_atomics" >&6; }
     rm -f conftest*
   fi
 
-  GLIBCXX_LANG_POP
+  CXXFLAGS="$old_CXXFLAGS"
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext 
$LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
 
   if test "$glibcxx_cv_libbacktrace_atomics" = yes; then
     BACKTRACE_CPPFLAGS="$BACKTRACE_CPPFLAGS -DHAVE_ATOMIC_FUNCTIONS=1"
-- 
2.49.0