[PATCH] libstdc++: Replace AC_LANG_CPLUSPLUS with AC_LANG_PUSH

Tomasz Kaminski tkaminsk@redhat.com
Wed Apr 30 05:15:57 GMT 2025


On Fri, Apr 25, 2025 at 10:06 PM Jonathan Wakely <jwakely@redhat.com> wrote:

> Autoconf documents AC_LANG_SAVE, AC_LANG_CPLUSPLUS etc. as deprecated.
>
> libstdc++-v3/ChangeLog:
>
>         * acinclude.m4 (GLIBCXX_LANG_PUSH, GLIBCXX_LANG_POP): New
>         macros to replace uses of AC_LANG_SAVE, AC_LANG_CPLUSPLUS, and
>         AC_LANG_RESTORE.
>         * configure: Regenerate.
> ---
>
> Tomasz pointed out that we're using deprecated macros. This would
> replace them with the modern Autoconf macros, but I'm not sure it's
> really an improvement, or necessary.
>
> Should we bother?
>
I find this commit to be a nice simplification, with GLIBCXX_LANG_PUSH and
GLIBCXX_LANG_POP,
so I would go with it.

>
> Tested x86_64-linux.
>
>  libstdc++-v3/acinclude.m4 | 290 +++++++++++++----------------------
>  libstdc++-v3/configure    | 307 ++++++++++++++++++++++++++++++--------
>  2 files changed, 349 insertions(+), 248 deletions(-)
>
> diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
> index a0094c2dd95..86f974feb6f 100644
> --- a/libstdc++-v3/acinclude.m4
> +++ b/libstdc++-v3/acinclude.m4
> @@ -118,6 +118,27 @@ AC_DEFUN([GLIBCXX_CONFIGURE], [
>    GLIBCXX_CHECK_HOST
>  ])
>
> +dnl
> +dnl Sets the current language for compilation tests to C++ and saves the
> +dnl current values of CXXFLAGS and LIBS so they can be restored
> afterwards.
> +dnl This should be paired with GLIBCXX_LANG_POP.
> +dnl
> +AC_DEFUN([GLIBCXX_LANG_PUSH],[
> +  AC_LANG_PUSH(C++)
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +])
> +
> +dnl
> +dnl Restores the current language for compilation tests to the previous
> value
> +dnl and restores the previous values of CXXFLAGS and LIBS.
> +dnl This should be paired with GLIBCXX_LANG_PUSH.
> +dnl
> +AC_DEFUN([GLIBCXX_LANG_POP],[
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
> +  AC_LANG_POP(C++)
> +])
>
>  dnl
>  dnl Tests for newer compiler features, or features that are present in
> newer
> @@ -135,27 +156,18 @@ AC_DEFUN([GLIBCXX_CHECK_COMPILER_FEATURES], [
>    # All these tests are for C++; save the language and the compiler flags.
>    # The CXXFLAGS thing is suspicious, but based on similar bits previously
>    # found in GLIBCXX_CONFIGURE.
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_test_CXXFLAGS="${CXXFLAGS+set}"
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>
>    # Check for -ffunction-sections -fdata-sections
>    AC_MSG_CHECKING([for g++ that supports -ffunction-sections
> -fdata-sections])
>    CXXFLAGS='-g -Werror -ffunction-sections -fdata-sections'
>    AC_TRY_COMPILE([int foo; void bar() { };],, [ac_fdsections=yes],
> [ac_fdsections=no])
> -  if test "$ac_test_CXXFLAGS" = set; then
> -    CXXFLAGS="$ac_save_CXXFLAGS"
> -  else
> -    # this is the suspicious part
> -    CXXFLAGS=''
> -  fi
>    if test x"$ac_fdsections" = x"yes"; then
>      SECTION_FLAGS='-ffunction-sections -fdata-sections'
>    fi
>    AC_MSG_RESULT($ac_fdsections)
>
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>    AC_SUBST(SECTION_FLAGS)
>  ])
>
> @@ -329,8 +341,7 @@ AC_DEFUN([GLIBCXX_CHECK_SETRLIMIT_ancilliary], [
>  ])
>
>  AC_DEFUN([GLIBCXX_CHECK_SETRLIMIT], [
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +  GLIBCXX_LANG_PUSH
>    setrlimit_have_headers=yes
>    AC_CHECK_HEADERS(unistd.h sys/time.h sys/resource.h,
>                    [],
> @@ -364,7 +375,7 @@ AC_DEFUN([GLIBCXX_CHECK_SETRLIMIT], [
>                 "make check"])
>      fi
>    fi
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>
> @@ -374,9 +385,7 @@ dnl Define HAVE_S_ISREG / HAVE_S_IFREG appropriately.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_S_ISREG_OR_S_IFREG], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    AC_MSG_CHECKING([for S_ISREG or S_IFREG])
> @@ -410,8 +419,7 @@ AC_DEFUN([GLIBCXX_CHECK_S_ISREG_OR_S_IFREG], [
>    fi
>    AC_MSG_RESULT($res)
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>
> @@ -420,9 +428,7 @@ dnl Check whether poll is available in <poll.h>, and
> define HAVE_POLL.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_POLL], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    AC_CACHE_CHECK([for poll], glibcxx_cv_POLL, [
> @@ -438,8 +444,7 @@ AC_DEFUN([GLIBCXX_CHECK_POLL], [
>      AC_DEFINE(HAVE_POLL, 1, [Define if poll is available in <poll.h>.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>
> @@ -448,9 +453,7 @@ dnl Check whether writev is available in <sys/uio.h>,
> and define HAVE_WRITEV.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_WRITEV], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    AC_CACHE_CHECK([for writev], glibcxx_cv_WRITEV, [
> @@ -465,8 +468,7 @@ AC_DEFUN([GLIBCXX_CHECK_WRITEV], [
>      AC_DEFINE(HAVE_WRITEV, 1, [Define if writev is available in
> <sys/uio.h>.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>
> @@ -474,9 +476,7 @@ dnl
>  dnl Check whether LFS support is available.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_LFS], [
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    AC_CACHE_CHECK([for LFS support], glibcxx_cv_LFS, [
>      GCC_TRY_COMPILE_OR_LINK(
> @@ -513,8 +513,7 @@ AC_DEFUN([GLIBCXX_CHECK_LFS], [
>      AC_DEFINE(_GLIBCXX_USE_FSEEKO_FTELLO, 1, [Define if fseeko and ftello
> are available.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>
> @@ -866,15 +865,12 @@ AC_DEFUN([GLIBCXX_ENABLE_C99], [
>    GLIBCXX_ENABLE(c99,$1,,[turns on ISO/IEC 9899:1999 support])
>
>    if test x"$enable_c99" = x"yes"; then
> -    AC_LANG_SAVE
> -    AC_LANG_CPLUSPLUS
> +    GLIBCXX_LANG_PUSH
>
>      # Use -std=c++98 (instead of -std=gnu++98) because leaving
> __STRICT_ANSI__
>      # undefined may cause fake C99 facilities, like pre-standard snprintf,
>      # to be spuriously enabled.
> -    ac_save_CXXFLAGS="$CXXFLAGS"
>      CXXFLAGS="$CXXFLAGS -std=c++98"
> -    ac_save_LIBS="$LIBS"
>      ac_save_gcc_no_link="$gcc_no_link"
>
>      if test x$gcc_no_link != xyes; then
> @@ -1095,18 +1091,13 @@ AC_DEFUN([GLIBCXX_ENABLE_C99], [
>      fi
>
>      gcc_no_link="$ac_save_gcc_no_link"
> -    LIBS="$ac_save_LIBS"
> -    CXXFLAGS="$ac_save_CXXFLAGS"
> -    AC_LANG_RESTORE
> +    GLIBCXX_LANG_POP
>
> -    AC_LANG_SAVE
> -    AC_LANG_CPLUSPLUS
> +    GLIBCXX_LANG_PUSH
>
>      # Use -std=c++11 and test again for C99 library feature in C++11 mode.
>      # For the reasons given above we use -std=c++11 not -std=gnu++11.
> -    ac_save_CXXFLAGS="$CXXFLAGS"
>      CXXFLAGS="$CXXFLAGS -std=c++11"
> -    ac_save_LIBS="$LIBS"
>      ac_save_gcc_no_link="$gcc_no_link"
>
>      if test x$gcc_no_link != xyes; then
> @@ -1709,9 +1700,7 @@ AC_DEFUN([GLIBCXX_ENABLE_C99], [
>      fi
>
>      gcc_no_link="$ac_save_gcc_no_link"
> -    LIBS="$ac_save_LIBS"
> -    CXXFLAGS="$ac_save_CXXFLAGS"
> -    AC_LANG_RESTORE
> +    GLIBCXX_LANG_POP
>    fi
>
>    AC_MSG_CHECKING([for fully enabled ISO C99 support])
> @@ -1749,11 +1738,8 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
>      [use KIND for check type],
>      [permit yes|no|rt])
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
> -  ac_save_LIBS="$LIBS"
>
>    ac_has_clock_monotonic=no
>    ac_has_clock_realtime=no
> @@ -1984,9 +1970,7 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_TIME], [
>
>    AC_SUBST(GLIBCXX_LIBS)
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  LIBS="$ac_save_LIBS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -1997,9 +1981,7 @@ AC_DEFUN([GLIBCXX_CHECK_GETTIMEOFDAY], [
>
>    AC_MSG_CHECKING([for gettimeofday])
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    ac_has_gettimeofday=no;
> @@ -2018,8 +2000,7 @@ AC_DEFUN([GLIBCXX_CHECK_GETTIMEOFDAY], [
>        [ Defined if gettimeofday is available. ])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -2028,12 +2009,10 @@ dnl facilities in Chapter 8, "C compatibility".
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_C99_TR1], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +  GLIBCXX_LANG_PUSH
>
>    # Use -std=c++98 because -std=gnu++98 leaves __STRICT_ANSI__
>    # undefined and fake C99 facilities may be spuriously enabled.
> -  ac_save_CXXFLAGS="$CXXFLAGS"
>    CXXFLAGS="$CXXFLAGS -std=c++98"
>
>    # Check for the existence of <complex.h> complex math functions used
> @@ -2389,8 +2368,7 @@ AC_DEFUN([GLIBCXX_CHECK_C99_TR1], [
>    # Check for the existence of the <stdalign.h> header.
>    AC_CHECK_HEADERS(stdalign.h)
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -2401,9 +2379,7 @@ AC_DEFUN([GLIBCXX_CHECK_UCHAR_H], [
>    # Test uchar.h.
>    AC_CHECK_HEADERS(uchar.h, ac_has_uchar_h=yes, ac_has_uchar_h=no)
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -std=c++11"
>
>    if test x"$ac_has_uchar_h" = x"yes"; then
> @@ -2478,8 +2454,7 @@ AC_DEFUN([GLIBCXX_CHECK_UCHAR_H], [
>               imported into namespace std in <cuchar> for C++20.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>
> @@ -2552,11 +2527,9 @@ dnl Check whether required C++ overloads are
> present in <stdio.h>.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_STDIO_PROTO], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +  GLIBCXX_LANG_PUSH
>    # Use C++11 because a conforming <stdio.h> won't define gets for C++14,
>    # and we don't need a declaration for C++14 anyway.
> -  ac_save_CXXFLAGS="$CXXFLAGS"
>    CXXFLAGS="$CXXFLAGS -std=gnu++11"
>
>    AC_CACHE_CHECK([for gets declaration], glibcxx_cv_gets, [
> @@ -2575,8 +2548,7 @@ AC_DEFUN([GLIBCXX_CHECK_STDIO_PROTO], [
>      AC_DEFINE(HAVE_GETS, 1, [Define if gets is available in <stdio.h>
> before C++14.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -2585,9 +2557,7 @@ dnl types are present in <math.h>.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_MATH11_PROTO], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -std=c++11"
>
>    case "$host" in
> @@ -2721,8 +2691,7 @@ AC_DEFUN([GLIBCXX_CHECK_MATH11_PROTO], [
>        ;;
>    esac
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -3507,8 +3476,7 @@ dnl  ENABLE_FLOAT128
>  dnl
>  AC_DEFUN([GLIBCXX_ENABLE_FLOAT128], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +  GLIBCXX_LANG_PUSH
>
>    # Fake what AC_TRY_COMPILE does, without linking as this is
>    # unnecessary for this test.
> @@ -3539,7 +3507,7 @@ EOF
>      GLIBCXX_CONDITIONAL(ENABLE_FLOAT128, test $enable_float128 = yes)
>      rm -f conftest*
>
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -3572,8 +3540,7 @@ AC_DEFUN([GLIBCXX_ENABLE_WCHAR_T], [
>
>    if test x"$enable_wchar_t" = x"yes"; then
>
> -    AC_LANG_SAVE
> -    AC_LANG_CPLUSPLUS
> +    GLIBCXX_LANG_PUSH
>
>      if test x"$ac_has_wchar_h" = xyes &&
>         test x"$ac_has_wctype_h" = xyes; then
> @@ -3643,7 +3610,7 @@ AC_DEFUN([GLIBCXX_ENABLE_WCHAR_T], [
>        enable_wchar_t=no
>      fi
>
> -    AC_LANG_RESTORE
> +    GLIBCXX_LANG_POP
>    fi
>
>    if test x"$enable_wchar_t" = x"yes"; then
> @@ -3675,10 +3642,8 @@ AC_DEFUN([GLIBCXX_ENABLE_PCH], [
>    if test $enable_libstdcxx_pch = yes; then
>      AC_CACHE_CHECK([for compiler with PCH support],
>        [glibcxx_cv_prog_CXX_pch],
> -      [ac_save_CXXFLAGS="$CXXFLAGS"
> +      [GLIBCXX_LANG_PUSH
>         CXXFLAGS="$CXXFLAGS -Werror -Winvalid-pch -Wno-deprecated"
> -       AC_LANG_SAVE
> -       AC_LANG_CPLUSPLUS
>         echo '#include <math.h>' > conftest.h
>         if $CXX $CXXFLAGS $CPPFLAGS -x c++-header conftest.h \
>                           -o conftest.h.gch 1>&5 2>&1 &&
> @@ -3691,8 +3656,7 @@ AC_DEFUN([GLIBCXX_ENABLE_PCH], [
>          glibcxx_cv_prog_CXX_pch=no
>         fi
>         rm -f conftest*
> -       CXXFLAGS=$ac_save_CXXFLAGS
> -       AC_LANG_RESTORE
> +       GLIBCXX_LANG_POP
>        ])
>      enable_libstdcxx_pch=$glibcxx_cv_prog_CXX_pch
>    fi
> @@ -3724,9 +3688,9 @@ dnl Note:
>  dnl libgomp and libgfortran use a link test, see CHECK_SYNC_FETCH_AND_ADD.
>  dnl
>  AC_DEFUN([GLIBCXX_ENABLE_ATOMIC_BUILTINS], [
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  old_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
> +  # Compile unoptimized.
> +  CXXFLAGS='-O0'
>
>    # Do link tests if possible, instead asm tests, limited to some
> platforms
>    # see discussion in PR target/40134, PR libstdc++/40133 and the thread
> @@ -3947,8 +3911,7 @@ EOF
>
>    fi
>
> -  CXXFLAGS="$old_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>
>    # Set atomicity_dir to builtins if all but the long long test above
> passes,
>    # or if the builtins were already chosen (e.g. by configure.host).
> @@ -4015,9 +3978,7 @@ AC_DEFUN([GLIBCXX_ENABLE_LOCK_POLICY], [
>    AC_MSG_CHECKING([for lock policy for shared_ptr reference counts])
>
>    if test x"$libstdcxx_atomic_lock_policy" = x"auto"; then
> -    AC_LANG_SAVE
> -    AC_LANG_CPLUSPLUS
> -    ac_save_CXXFLAGS="$CXXFLAGS"
> +    GLIBCXX_LANG_PUSH
>
>      dnl Why do we care about 2-byte CAS on targets with 4-byte
> _Atomic_word?!
>      dnl Why don't we check 8-byte CAS for sparc64, where _Atomic_word is
> long?!
> @@ -4035,8 +3996,7 @@ AC_DEFUN([GLIBCXX_ENABLE_LOCK_POLICY], [
>      ],,
>      [libstdcxx_atomic_lock_policy=atomic],
>      [libstdcxx_atomic_lock_policy=mutex])
> -    AC_LANG_RESTORE
> -    CXXFLAGS="$ac_save_CXXFLAGS"
> +    GLIBCXX_LANG_POP
>    fi
>
>    if test x"$libstdcxx_atomic_lock_policy" = x"atomic"; then
> @@ -4365,10 +4325,8 @@ AC_DEFUN([GLIBCXX_CHECK_GTHREADS], [
>    if test x$enable_libstdcxx_threads = xauto ||
>       test x$enable_libstdcxx_threads = xyes; then
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +  GLIBCXX_LANG_PUSH
>
> -  ac_save_CXXFLAGS="$CXXFLAGS"
>    CXXFLAGS="$CXXFLAGS -fno-exceptions \
>         -I${toplevel_srcdir}/libgcc -I${toplevel_builddir}/libgcc"
>
> @@ -4488,8 +4446,7 @@ AC_DEFUN([GLIBCXX_CHECK_GTHREADS], [
>    fi
>    AC_MSG_RESULT([$ac_have_posix_semaphore])
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>
> @@ -4555,9 +4512,7 @@ dnl Check whether get_nprocs is available in
> <sys/sysinfo.h>, and define _GLIBCX
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_GET_NPROCS], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    AC_CACHE_CHECK([for get_nprocs],
> @@ -4572,8 +4527,7 @@ AC_DEFUN([GLIBCXX_CHECK_GET_NPROCS], [
>      AC_DEFINE(_GLIBCXX_USE_GET_NPROCS, 1, [Define if get_nprocs is
> available in <sys/sysinfo.h>.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -4581,9 +4535,7 @@ dnl Check whether sysconf(_SC_NPROCESSORS_ONLN) is
> available in <unistd.h>, and
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_SC_NPROCESSORS_ONLN], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    AC_CACHE_CHECK([for _SC_NPROCESSORS_ONLN],
> @@ -4598,8 +4550,7 @@ AC_DEFUN([GLIBCXX_CHECK_SC_NPROCESSORS_ONLN], [
>      AC_DEFINE(_GLIBCXX_USE_SC_NPROCESSORS_ONLN, 1, [Define if
> _SC_NPROCESSORS_ONLN  is available in <unistd.h>.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -4607,9 +4558,7 @@ dnl Check whether sysconf(_SC_NPROC_ONLN) is
> available in <unistd.h>, and define
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_SC_NPROC_ONLN], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    AC_CACHE_CHECK([for _SC_NPROC_ONLN],
> @@ -4624,8 +4573,7 @@ AC_DEFUN([GLIBCXX_CHECK_SC_NPROC_ONLN], [
>      AC_DEFINE(_GLIBCXX_USE_SC_NPROC_ONLN, 1, [Define if _SC_NPROC_ONLN
> is available in <unistd.h>.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -4633,9 +4581,7 @@ dnl Check whether pthread_num_processors_np is
> available in <pthread.h>, and def
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_PTHREADS_NUM_PROCESSORS_NP], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    AC_CACHE_CHECK([for pthreads_num_processors_np],
> @@ -4650,8 +4596,7 @@ AC_DEFUN([GLIBCXX_CHECK_PTHREADS_NUM_PROCESSORS_NP],
> [
>      AC_DEFINE(_GLIBCXX_USE_PTHREADS_NUM_PROCESSORS_NP, 1, [Define if
> pthreads_num_processors_np is available in <pthread.h>.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -4660,11 +4605,8 @@ dnl and define _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_PTHREAD_COND_CLOCKWAIT], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
> -  ac_save_LIBS="$LIBS"
>    LIBS="$LIBS -lpthread"
>
>    AC_CACHE_CHECK([for pthread_cond_clockwait],
> @@ -4679,9 +4621,7 @@ AC_DEFUN([GLIBCXX_CHECK_PTHREAD_COND_CLOCKWAIT], [
>      AC_DEFINE(_GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT, 1, [Define if
> pthread_cond_clockwait is available in <pthread.h>.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  LIBS="$ac_save_LIBS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -4690,11 +4630,8 @@ dnl and define _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
> -  ac_save_LIBS="$LIBS"
>    LIBS="$LIBS -lpthread"
>
>    AC_CACHE_CHECK([for pthread_mutex_clocklock],
> @@ -4709,9 +4646,7 @@ AC_DEFUN([GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK], [
>      AC_DEFINE(_GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK, (_GLIBCXX_TSAN==0),
> [Define if pthread_mutex_clocklock is available in <pthread.h>.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  LIBS="$ac_save_LIBS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -4720,11 +4655,8 @@ dnl and define _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_PTHREAD_RWLOCK_CLOCKLOCK], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
> -  ac_save_LIBS="$LIBS"
>    LIBS="$LIBS -lpthread"
>
>    AC_CACHE_CHECK([for pthread_rwlock_clockrdlock,
> pthread_wlock_clockwrlock],
> @@ -4741,9 +4673,7 @@ AC_DEFUN([GLIBCXX_CHECK_PTHREAD_RWLOCK_CLOCKLOCK], [
>      AC_DEFINE(_GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK, 1, [Define if
> pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock are available in
> <pthread.h>.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  LIBS="$ac_save_LIBS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -4751,9 +4681,7 @@ dnl Check whether sysctl is available in
> <pthread.h>, and define _GLIBCXX_USE_SY
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_SYSCTL_HW_NCPU], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    AC_CACHE_CHECK([for hw.ncpu sysctl],
> @@ -4776,8 +4704,7 @@ AC_DEFUN([GLIBCXX_CHECK_SYSCTL_HW_NCPU], [
>      AC_DEFINE(_GLIBCXX_USE_SYSCTL_HW_NCPU, 1, [Define if sysctl(), CTL_HW
> and HW_NCPU are available in <sys/sysctl.h>.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -4817,9 +4744,7 @@ dnl and define _GLIBCXX_USE_TMPNAM.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_TMPNAM], [dnl
>  dnl
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>  dnl
>    AC_CACHE_CHECK([for tmpnam], glibcxx_cv_TMPNAM, [dnl
> @@ -4833,8 +4758,7 @@ dnl
>      AC_DEFINE(_GLIBCXX_USE_TMPNAM, 1, [Define if obsolescent tmpnam is
> available in <stdio.h>.])
>    fi
>  dnl
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -4845,8 +4769,7 @@ AC_DEFUN([GLIBCXX_CHECK_SDT_H], [
>    # Note that this test has to be run with the C language.
>    # Otherwise, sdt.h will try to include some headers from
>    # libstdc++ itself.
> -  AC_LANG_SAVE
> -  AC_LANG_C
> +  AC_LANG_PUSH(C)
>    AC_CACHE_CHECK([for suitable sys/sdt.h],
>      glibcxx_cv_sys_sdt_h, [
>      # Because we have to run the test in C, we use grep rather
> @@ -4859,7 +4782,7 @@ AC_DEFUN([GLIBCXX_CHECK_SDT_H], [
>        int f() { STAP_PROBE(hi, bob); }
>      ], [glibcxx_cv_sys_sdt_h=yes], [glibcxx_cv_sys_sdt_h=no])
>    ])
> -  AC_LANG_RESTORE
> +  AC_LANG_POP(C)
>    if test $glibcxx_cv_sys_sdt_h = yes; then
>      AC_DEFINE(HAVE_SYS_SDT_H, 1,
>                [Define to 1 if you have a suitable <sys/sdt.h> header
> file])
> @@ -4982,9 +4905,7 @@ dnl  HAVE_SYMLINK
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_FILESYSTEM_DEPS], [dnl
>  dnl
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>  dnl
>    AC_CACHE_CHECK([for struct dirent.d_type], glibcxx_cv_dirent_d_type,
> [dnl
> @@ -5320,8 +5241,7 @@ dnl
>      AC_DEFINE(HAVE_UNLINKAT, 1, [Define if unlinkat is available in
> <fcntl.h>.])
>    fi
>  dnl
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -5398,8 +5318,7 @@ dnl Check whether getentropy is present in
> <unistd.h>.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_GETENTROPY], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +  GLIBCXX_LANG_PUSH
>    AC_CACHE_CHECK([for getentropy], glibcxx_cv_getentropy, [
>        GCC_TRY_COMPILE_OR_LINK(
>         [#include <unistd.h>],
> @@ -5411,7 +5330,7 @@ AC_DEFUN([GLIBCXX_CHECK_GETENTROPY], [
>    if test $glibcxx_cv_getentropy = yes; then
>      AC_DEFINE(HAVE_GETENTROPY, 1, [Define if getentropy is available in
> <unistd.h>.])
>    fi
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -5419,8 +5338,7 @@ dnl Check whether arc4random is present in
> <stdlib.h>.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_ARC4RANDOM], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +  GLIBCXX_LANG_PUSH
>    AC_CACHE_CHECK([for arc4random], glibcxx_cv_arc4random, [
>        GCC_TRY_COMPILE_OR_LINK(
>         [#include <stdlib.h>],
> @@ -5431,7 +5349,7 @@ AC_DEFUN([GLIBCXX_CHECK_ARC4RANDOM], [
>    if test $glibcxx_cv_arc4random = yes; then
>      AC_DEFINE(HAVE_ARC4RANDOM, 1, [Define if arc4random is available in
> <stdlib.h>.])
>    fi
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -5756,9 +5674,7 @@ dnl  _GLIBCXX_USE_STRUCT_TM_TM_ZONE if struct tm has
> a tm_zone member.
>  dnl
>  AC_DEFUN([GLIBCXX_STRUCT_TM_TM_ZONE], [
>
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> +  GLIBCXX_LANG_PUSH
>    CXXFLAGS="$CXXFLAGS -std=c++20"
>
>    AC_CACHE_CHECK([for tm_zone member of struct tm], glibcxx_cv_tm_zone, [
> @@ -5776,8 +5692,7 @@ AC_DEFUN([GLIBCXX_STRUCT_TM_TM_ZONE], [
>               [Define if struct tm has a tm_zone member.])
>    fi
>
> -  CXXFLAGS="$ac_save_CXXFLAGS"
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -5788,8 +5703,7 @@ dnl  _GLIBCXX_CAN_ALIGNAS_DESTRUCTIVE_SIZE if
> objects with static storage
>  dnl    duration can be aligned to
> std::hardware_destructive_interference_size.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_ALIGNAS_CACHELINE], [
> -  AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +  GLIBCXX_LANG_PUSH
>
>    AC_MSG_CHECKING([whether static objects can be aligned to the cacheline
> size])
>    AC_TRY_COMPILE(, [struct alignas(__GCC_DESTRUCTIVE_SIZE) Aligned { };
> @@ -5802,7 +5716,7 @@ AC_DEFUN([GLIBCXX_CHECK_ALIGNAS_CACHELINE], [
>    fi
>    AC_MSG_RESULT($ac_alignas_cacheline)
>
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -5814,8 +5728,8 @@ dnl  _GLIBCXX_USE_INIT_PRIORITY_ATTRIBUTE if GCC
> supports the init_priority
>  dnl    attribute for the target.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_INIT_PRIORITY], [
> -AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +
> +  GLIBCXX_LANG_PUSH
>
>    AC_MSG_CHECKING([whether init_priority attribute is supported])
>    AC_TRY_COMPILE(, [
> @@ -5829,7 +5743,7 @@ AC_LANG_SAVE
>    fi
>    AC_MSG_RESULT($ac_init_priority)
>
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -5839,8 +5753,8 @@ dnl Defines:
>  dnl   _GLIBCXX_USE__GET_OSFHANDLE if _get_osfhandle is in <io.h> for
> Windows.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_FILEBUF_NATIVE_HANDLES], [
> -AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +
> +  GLIBCXX_LANG_PUSH
>
>    AC_MSG_CHECKING([whether _get_osfhandle is defined in <io.h>])
>    AC_TRY_COMPILE([
> @@ -5861,7 +5775,7 @@ AC_LANG_SAVE
>    fi
>    AC_MSG_RESULT($ac_get_osfhandle)
>
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  dnl
> @@ -5871,8 +5785,8 @@ dnl Defines:
>  dnl   _GLIBCXX_USE_NL_LANGINFO_L if nl_langinfo_l is in <langinfo.h>.
>  dnl
>  AC_DEFUN([GLIBCXX_CHECK_TEXT_ENCODING], [
> -AC_LANG_SAVE
> -  AC_LANG_CPLUSPLUS
> +
> +  GLIBCXX_LANG_PUSH
>
>    AC_MSG_CHECKING([whether nl_langinfo_l is defined in <langinfo.h>])
>    AC_TRY_COMPILE([
> @@ -5892,7 +5806,7 @@ AC_LANG_SAVE
>        [Define if nl_langinfo_l should be used for std::text_encoding.])
>    fi
>
> -  AC_LANG_RESTORE
> +  GLIBCXX_LANG_POP
>  ])
>
>  # Macros from the top-level gcc directory.
> diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
> index 819a1d82876..ea0d5e1bf8e 100755
> --- a/libstdc++-v3/configure
> +++ b/libstdc++-v3/configure
> @@ -15907,15 +15907,17 @@ $as_echo_n "checking for compiler with PCH
> support... " >&6; }
>  if ${glibcxx_cv_prog_CXX_pch+:} false; then :
>    $as_echo_n "(cached) " >&6
>  else
> -  ac_save_CXXFLAGS="$CXXFLAGS"
> -       CXXFLAGS="$CXXFLAGS -Werror -Winvalid-pch -Wno-deprecated"
>
> -       ac_ext=cpp
> +  ac_ext=cpp
>  ac_cpp='$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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
> +       CXXFLAGS="$CXXFLAGS -Werror -Winvalid-pch -Wno-deprecated"
>         echo '#include <math.h>' > conftest.h
>         if $CXX $CXXFLAGS $CPPFLAGS -x c++-header conftest.h \
>                           -o conftest.h.gch 1>&5 2>&1 &&
> @@ -15928,14 +15930,17 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>          glibcxx_cv_prog_CXX_pch=no
>         fi
>         rm -f conftest*
> -       CXXFLAGS=$ac_save_CXXFLAGS
> -       ac_ext=c
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
> +  ac_ext=c
>  ac_cpp='$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
>
>
> +
>  fi
>  { $as_echo "$as_me:${as_lineno-$LINENO}: result:
> $glibcxx_cv_prog_CXX_pch" >&5
>  $as_echo "$glibcxx_cv_prog_CXX_pch" >&6; }
> @@ -15987,7 +15992,11 @@ 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="$CXXFLAGS"
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
> +  # Compile unoptimized.
> +  CXXFLAGS='-O0'
>
>    # Do link tests if possible, instead asm tests, limited to some
> platforms
>    # see discussion in PR target/40134, PR libstdc++/40133 and the thread
> @@ -16182,7 +16191,7 @@ $as_echo "$glibcxx_cv_atomic_long_long" >&6; }
>    # Fake what AC_TRY_COMPILE does.
>
>      cat > conftest.$ac_ext << EOF
> -#line 16185 "configure"
> +#line 16194 "configure"
>  int main()
>  {
>    typedef bool atomic_type;
> @@ -16217,7 +16226,7 @@ $as_echo "$glibcxx_cv_atomic_bool" >&6; }
>      rm -f conftest*
>
>      cat > conftest.$ac_ext << EOF
> -#line 16220 "configure"
> +#line 16229 "configure"
>  int main()
>  {
>    typedef short atomic_type;
> @@ -16252,7 +16261,7 @@ $as_echo "$glibcxx_cv_atomic_short" >&6; }
>      rm -f conftest*
>
>      cat > conftest.$ac_ext << EOF
> -#line 16255 "configure"
> +#line 16264 "configure"
>  int main()
>  {
>    // NB: _Atomic_word not necessarily int.
> @@ -16288,7 +16297,7 @@ $as_echo "$glibcxx_cv_atomic_int" >&6; }
>      rm -f conftest*
>
>      cat > conftest.$ac_ext << EOF
> -#line 16291 "configure"
> +#line 16300 "configure"
>  int main()
>  {
>    typedef long long atomic_type;
> @@ -16324,7 +16333,9 @@ $as_echo "$glibcxx_cv_atomic_long_long" >&6; }
>
>    fi
>
> -  CXXFLAGS="$old_CXXFLAGS"
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -16332,6 +16343,7 @@ ac_link='$CC -o conftest$ac_exeext $CFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ext $
>  ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
> +
>    # Set atomicity_dir to builtins if all but the long long test above
> passes,
>    # or if the builtins were already chosen (e.g. by configure.host).
>    if { test "$glibcxx_cv_atomic_bool" = yes \
> @@ -16383,13 +16395,15 @@ $as_echo_n "checking for lock policy for
> shared_ptr reference counts... " >&6; }
>
>    if test x"$libstdcxx_atomic_lock_policy" = x"auto"; then
>
> -    ac_ext=cpp
> +  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
>
> -    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>                  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
>  /* end confdefs.h.  */
> @@ -16418,13 +16432,16 @@ else
>    libstdcxx_atomic_lock_policy=mutex
>  fi
>  rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
> -    ac_ext=c
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
> +  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
>
> -    CXXFLAGS="$ac_save_CXXFLAGS"
> +
>    fi
>
>    if test x"$libstdcxx_atomic_lock_policy" = x"atomic"; then
> @@ -16445,7 +16462,7 @@ $as_echo "mutex" >&6; }
>    # unnecessary for this test.
>
>      cat > conftest.$ac_ext << EOF
> -#line 16448 "configure"
> +#line 16465 "configure"
>  int main()
>  {
>    _Decimal32 d1;
> @@ -16482,12 +16499,15 @@ 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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>    # Fake what AC_TRY_COMPILE does, without linking as this is
>    # unnecessary for this test.
>
>    cat > conftest.$ac_ext << EOF
> -#line 16490 "configure"
> +#line 16510 "configure"
>  template<typename T1, typename T2>
>    struct same
>    { typedef T2 type; };
> @@ -16518,6 +16538,9 @@ $as_echo "$enable_float128" >&6; }
>
>      rm -f conftest*
>
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -16525,6 +16548,7 @@ ac_link='$CC -o conftest$ac_exeext $CFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ext $
>  ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
> +
>  if test "$enable_float128" = yes; then
>    port_specific_symbol_files="$port_specific_symbol_files
> \$(top_srcdir)/config/abi/pre/float128.ver"
>  fi
> @@ -16541,8 +16565,9 @@ ac_compile='$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
>
> -  ac_test_CXXFLAGS="${CXXFLAGS+set}"
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>    # Check for -ffunction-sections -fdata-sections
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for g++ that supports
> -ffunction-sections -fdata-sections" >&5
> @@ -16565,18 +16590,15 @@ else
>    ac_fdsections=no
>  fi
>  rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
> -  if test "$ac_test_CXXFLAGS" = set; then
> -    CXXFLAGS="$ac_save_CXXFLAGS"
> -  else
> -    # this is the suspicious part
> -    CXXFLAGS=''
> -  fi
>    if test x"$ac_fdsections" = x"yes"; then
>      SECTION_FLAGS='-ffunction-sections -fdata-sections'
>    fi
>    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_fdsections" >&5
>  $as_echo "$ac_fdsections" >&6; }
>
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -16586,6 +16608,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # Enable all the variable C++ runtime options that don't require linking.
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for underlying I/O to
> use" >&5
> @@ -17284,12 +17307,15 @@ done
>    if test x"$enable_wchar_t" = x"yes"; then
>
>
> -    ac_ext=cpp
> +  ac_ext=cpp
>  ac_cpp='$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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>      if test x"$ac_has_wchar_h" = xyes &&
>         test x"$ac_has_wctype_h" = xyes; then
> @@ -17375,12 +17401,16 @@ rm -f core conftest.err conftest.$ac_objext
> conftest.$ac_ext
>        enable_wchar_t=no
>      fi
>
> -    ac_ext=c
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
> +  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
>
> +
>    fi
>
>    if test x"$enable_wchar_t" = x"yes"; then
> @@ -17412,19 +17442,20 @@ fi
>
>    if test x"$enable_c99" = x"yes"; then
>
> -    ac_ext=cpp
> +  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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>      # Use -std=c++98 (instead of -std=gnu++98) because leaving
> __STRICT_ANSI__
>      # undefined may cause fake C99 facilities, like pre-standard snprintf,
>      # to be spuriously enabled.
> -    ac_save_CXXFLAGS="$CXXFLAGS"
>      CXXFLAGS="$CXXFLAGS -std=c++98"
> -    ac_save_LIBS="$LIBS"
>      ac_save_gcc_no_link="$gcc_no_link"
>
>      if test x$gcc_no_link != xyes; then
> @@ -18079,9 +18110,10 @@ $as_echo "#define _GLIBCXX_USE_C99 1" >>confdefs.h
>      fi
>
>      gcc_no_link="$ac_save_gcc_no_link"
> -    LIBS="$ac_save_LIBS"
> -    CXXFLAGS="$ac_save_CXXFLAGS"
> -    ac_ext=c
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
> +  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 $LIBS >&5'
> @@ -18089,18 +18121,20 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> -    ac_ext=cpp
> +
> +  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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>      # Use -std=c++11 and test again for C99 library feature in C++11 mode.
>      # For the reasons given above we use -std=c++11 not -std=gnu++11.
> -    ac_save_CXXFLAGS="$CXXFLAGS"
>      CXXFLAGS="$CXXFLAGS -std=c++11"
> -    ac_save_LIBS="$LIBS"
>      ac_save_gcc_no_link="$gcc_no_link"
>
>      if test x$gcc_no_link != xyes; then
> @@ -19319,14 +19353,16 @@ $as_echo "#define _GLIBCXX_USE_C99_FENV 1"
> >>confdefs.h
>      fi
>
>      gcc_no_link="$ac_save_gcc_no_link"
> -    LIBS="$ac_save_LIBS"
> -    CXXFLAGS="$ac_save_CXXFLAGS"
> -    ac_ext=c
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
> +  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
>
> +
>    fi
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for fully enabled ISO
> C99 support" >&5
> @@ -19621,9 +19657,11 @@ 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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    # Use C++11 because a conforming <stdio.h> won't define gets for C++14,
>    # and we don't need a declaration for C++14 anyway.
> -  ac_save_CXXFLAGS="$CXXFLAGS"
>    CXXFLAGS="$CXXFLAGS -std=gnu++11"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for gets declaration"
> >&5
> @@ -19658,7 +19696,9 @@ $as_echo "#define HAVE_GETS 1" >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -19669,6 +19709,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    ac_ext=cpp
>  ac_cpp='$CXXCPP $CPPFLAGS'
>  ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -19676,6 +19717,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -std=c++11"
>
>    case "$host" in
> @@ -19857,7 +19900,9 @@ $as_echo "#define HAVE_OBSOLETE_ISNAN 1"
> >>confdefs.h
>        ;;
>    esac
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -19867,6 +19912,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    # Test uchar.h.
>    for ac_header in uchar.h
>  do :
> @@ -19891,6 +19937,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -std=c++11"
>
>    if test x"$ac_has_uchar_h" = x"yes"; then
> @@ -20014,7 +20062,9 @@ $as_echo "#define
> _GLIBCXX_USE_UCHAR_C8RTOMB_MBRTOC8_CXX20 1" >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -20023,6 +20073,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For LFS support.
>
>
> @@ -20033,6 +20084,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for LFS support" >&5
>  $as_echo_n "checking for LFS support... " >&6; }
> @@ -20174,7 +20227,9 @@ $as_echo "#define _GLIBCXX_USE_FSEEKO_FTELLO 1"
> >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -20183,6 +20238,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For showmanyc_helper().
>  for ac_header in sys/ioctl.h sys/filio.h
>  do :
> @@ -20207,6 +20263,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for poll" >&5
> @@ -20270,7 +20328,9 @@ $as_echo "#define HAVE_POLL 1" >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -20281,6 +20341,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    ac_ext=cpp
>  ac_cpp='$CXXCPP $CPPFLAGS'
>  ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -20288,6 +20349,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for S_ISREG or
> S_IFREG" >&5
> @@ -20411,7 +20474,9 @@ $as_echo "#define HAVE_S_IFREG 1" >>confdefs.h
>    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $res" >&5
>  $as_echo "$res" >&6; }
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -20420,6 +20485,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For xsputn_2().
>  for ac_header in sys/uio.h
>  do :
> @@ -20443,6 +20509,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for writev" >&5
> @@ -20504,7 +20572,9 @@ $as_echo "#define HAVE_WRITEV 1" >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -20513,6 +20583,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # Check for fenv.h and complex.h before GLIBCXX_CHECK_C99_TR1
>  # so that the check is done with the C compiler (not C++).
>  # Checking with C++ can break a canadian cross build if either
> @@ -20541,10 +20612,12 @@ ac_compile='$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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>    # Use -std=c++98 because -std=gnu++98 leaves __STRICT_ANSI__
>    # undefined and fake C99 facilities may be spuriously enabled.
> -  ac_save_CXXFLAGS="$CXXFLAGS"
>    CXXFLAGS="$CXXFLAGS -std=c++98"
>
>    # Check for the existence of <complex.h> complex math functions used
> @@ -21078,7 +21151,9 @@ fi
>  done
>
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -21087,6 +21162,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For the EOF, SEEK_CUR, and SEEK_END integer constants.
>
>
> @@ -21173,6 +21249,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    ac_has_gettimeofday=no;
> @@ -21245,7 +21323,9 @@ $as_echo "#define _GLIBCXX_USE_GETTIMEOFDAY 1"
> >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -21254,6 +21334,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For clock_gettime, nanosleep and sched_yield support.
>
>
> @@ -21279,9 +21360,10 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> -  CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    ac_save_LIBS="$LIBS"
>
> +  CXXFLAGS="$CXXFLAGS -fno-exceptions"
> +
>    ac_has_clock_monotonic=no
>    ac_has_clock_realtime=no
>    ac_has_nanosleep=no
> @@ -21898,6 +21980,7 @@ $as_echo "#define _GLIBCXX_NO_SLEEP 1" >>confdefs.h
>
>
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
>    LIBS="$ac_save_LIBS"
>    ac_ext=c
> @@ -21908,6 +21991,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # Check for tmpnam which is obsolescent in POSIX.1-2008
>
>    ac_ext=cpp
> @@ -21917,6 +22001,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for tmpnam" >&5
>  $as_echo_n "checking for tmpnam... " >&6; }
> @@ -21973,7 +22059,9 @@ $as_echo "$glibcxx_cv_TMPNAM" >&6; }
>  $as_echo "#define _GLIBCXX_USE_TMPNAM 1" >>confdefs.h
>
>    fi
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -21982,6 +22070,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For pthread_cond_clockwait
>
>
> @@ -21993,8 +22082,9 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> -  CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    ac_save_LIBS="$LIBS"
> +
> +  CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    LIBS="$LIBS -lpthread"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for
> pthread_cond_clockwait" >&5
> @@ -22054,6 +22144,7 @@ $as_echo "#define
> _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT 1" >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
>    LIBS="$ac_save_LIBS"
>    ac_ext=c
> @@ -22064,6 +22155,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For pthread_mutex_clocklock
>
>
> @@ -22075,8 +22167,9 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> -  CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    ac_save_LIBS="$LIBS"
> +
> +  CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    LIBS="$LIBS -lpthread"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for
> pthread_mutex_clocklock" >&5
> @@ -22136,6 +22229,7 @@ $as_echo "#define
> _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK (_GLIBCXX_TSAN==0)" >>con
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
>    LIBS="$ac_save_LIBS"
>    ac_ext=c
> @@ -22146,6 +22240,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For pthread_rwlock_clockrdlock and pthread_rwlock_clockwrlock
>
>
> @@ -22157,8 +22252,9 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> -  CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    ac_save_LIBS="$LIBS"
> +
> +  CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    LIBS="$LIBS -lpthread"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for
> pthread_rwlock_clockrdlock, pthread_wlock_clockwrlock" >&5
> @@ -22222,6 +22318,7 @@ $as_echo "#define
> _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK 1" >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
>    LIBS="$ac_save_LIBS"
>    ac_ext=c
> @@ -22233,6 +22330,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    ac_fn_c_check_header_mongrel "$LINENO" "locale.h"
> "ac_cv_header_locale_h" "$ac_includes_default"
>  if test "x$ac_cv_header_locale_h" = xyes; then :
>
> @@ -22295,6 +22393,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for get_nprocs" >&5
> @@ -22354,7 +22454,9 @@ $as_echo "#define _GLIBCXX_USE_GET_NPROCS 1"
> >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -22362,6 +22464,7 @@ ac_link='$CC -o conftest$ac_exeext $CFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ext $
>  ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
> +
>  for ac_header in unistd.h
>  do :
>    ac_fn_c_check_header_mongrel "$LINENO" "unistd.h"
> "ac_cv_header_unistd_h" "$ac_includes_default"
> @@ -22384,6 +22487,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for
> _SC_NPROCESSORS_ONLN" >&5
> @@ -22443,7 +22548,9 @@ $as_echo "#define _GLIBCXX_USE_SC_NPROCESSORS_ONLN
> 1" >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -22454,6 +22561,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    ac_ext=cpp
>  ac_cpp='$CXXCPP $CPPFLAGS'
>  ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -22461,6 +22569,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for _SC_NPROC_ONLN"
> >&5
> @@ -22520,7 +22630,9 @@ $as_echo "#define _GLIBCXX_USE_SC_NPROC_ONLN 1"
> >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -22531,6 +22643,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    ac_ext=cpp
>  ac_cpp='$CXXCPP $CPPFLAGS'
>  ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -22538,6 +22651,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for
> pthreads_num_processors_np" >&5
> @@ -22597,7 +22712,9 @@ $as_echo "#define
> _GLIBCXX_USE_PTHREADS_NUM_PROCESSORS_NP 1" >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -22608,6 +22725,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    ac_ext=cpp
>  ac_cpp='$CXXCPP $CPPFLAGS'
>  ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -22615,6 +22733,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for hw.ncpu sysctl"
> >&5
> @@ -22690,7 +22810,9 @@ $as_echo "#define _GLIBCXX_USE_SYSCTL_HW_NCPU 1"
> >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -22699,10 +22821,10 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    # Note that this test has to be run with the C language.
>    # Otherwise, sdt.h will try to include some headers from
>    # libstdc++ itself.
> -
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -28718,8 +28840,9 @@ 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
>
> -  ac_test_CXXFLAGS="${CXXFLAGS+set}"
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>    # Check for -ffunction-sections -fdata-sections
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for g++ that supports
> -ffunction-sections -fdata-sections" >&5
> @@ -28742,18 +28865,15 @@ else
>    ac_fdsections=no
>  fi
>  rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
> -  if test "$ac_test_CXXFLAGS" = set; then
> -    CXXFLAGS="$ac_save_CXXFLAGS"
> -  else
> -    # this is the suspicious part
> -    CXXFLAGS=''
> -  fi
>    if test x"$ac_fdsections" = x"yes"; then
>      SECTION_FLAGS='-ffunction-sections -fdata-sections'
>    fi
>    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_fdsections" >&5
>  $as_echo "$ac_fdsections" >&6; }
>
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -28763,6 +28883,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    # If we're not using GNU ld, then there's no point in even trying these
>    # tests.  Check for that first.  We should have already tested for gld
>    # by now (in libtool), but require it now just to be safe...
> @@ -38868,8 +38989,9 @@ ac_compile='$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
>
> -  ac_test_CXXFLAGS="${CXXFLAGS+set}"
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>    # Check for -ffunction-sections -fdata-sections
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for g++ that supports
> -ffunction-sections -fdata-sections" >&5
> @@ -38892,18 +39014,15 @@ else
>    ac_fdsections=no
>  fi
>  rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
> -  if test "$ac_test_CXXFLAGS" = set; then
> -    CXXFLAGS="$ac_save_CXXFLAGS"
> -  else
> -    # this is the suspicious part
> -    CXXFLAGS=''
> -  fi
>    if test x"$ac_fdsections" = x"yes"; then
>      SECTION_FLAGS='-ffunction-sections -fdata-sections'
>    fi
>    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_fdsections" >&5
>  $as_echo "$ac_fdsections" >&6; }
>
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -38913,6 +39032,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    # If we're not using GNU ld, then there's no point in even trying these
>    # tests.  Check for that first.  We should have already tested for gld
>    # by now (in libtool), but require it now just to be safe...
> @@ -51613,6 +51733,9 @@ ac_compile='$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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for getentropy" >&5
>  $as_echo_n "checking for getentropy... " >&6; }
>  if ${glibcxx_cv_getentropy+:} false; then :
> @@ -51672,6 +51795,9 @@ $as_echo "$glibcxx_cv_getentropy" >&6; }
>  $as_echo "#define HAVE_GETENTROPY 1" >>confdefs.h
>
>    fi
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -51682,12 +51808,16 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    ac_ext=cpp
>  ac_cpp='$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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for arc4random" >&5
>  $as_echo_n "checking for arc4random... " >&6; }
>  if ${glibcxx_cv_arc4random+:} false; then :
> @@ -51745,6 +51875,9 @@ $as_echo "$glibcxx_cv_arc4random" >&6; }
>  $as_echo "#define HAVE_ARC4RANDOM 1" >>confdefs.h
>
>    fi
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -51753,6 +51886,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # This depends on GLIBCXX_ENABLE_SYMVERS and GLIBCXX_IS_NATIVE.
>
>    # Do checks for resource limit functions.
> @@ -51764,6 +51898,9 @@ ac_compile='$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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    setrlimit_have_headers=yes
>    for ac_header in unistd.h sys/time.h sys/resource.h
>  do :
> @@ -51984,6 +52121,9 @@ $as_echo "#define _GLIBCXX_RES_LIMITS 1"
> >>confdefs.h
>
>      fi
>    fi
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -51992,6 +52132,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>    if $GLIBCXX_IS_NATIVE ; then
>      # Look for setenv, so that extended locale tests can be performed.
>
> @@ -52101,8 +52242,10 @@ ac_compile='$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
>
> -
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions \
>         -I${toplevel_srcdir}/libgcc -I${toplevel_builddir}/libgcc"
>
> @@ -52299,7 +52442,9 @@ $as_echo "#define HAVE_POSIX_SEMAPHORE 1"
> >>confdefs.h
>    { $as_echo "$as_me:${as_lineno-$LINENO}: result:
> $ac_have_posix_semaphore" >&5
>  $as_echo "$ac_have_posix_semaphore" >&6; }
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -52308,6 +52453,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For Filesystem TS.
>  for ac_header in fcntl.h dirent.h sys/statvfs.h utime.h
>  do :
> @@ -52376,6 +52522,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -fno-exceptions"
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for struct
> dirent.d_type" >&5
>  $as_echo_n "checking for struct dirent.d_type... " >&6; }
> @@ -53760,7 +53908,9 @@ $as_echo "$glibcxx_cv_unlinkat" >&6; }
>  $as_echo "#define HAVE_UNLINKAT 1" >>confdefs.h
>
>    fi
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -53770,6 +53920,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>     # Check whether --enable-libstdcxx-backtrace was given.
>  if test "${enable_libstdcxx_backtrace+set}" = set; then :
>    enableval=$enable_libstdcxx_backtrace;
> @@ -54437,6 +54588,8 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS
> $CPPFLAGS $LDFLAGS conftest.$ac_ex
>  ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
>
>    ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>    CXXFLAGS="$CXXFLAGS -std=c++20"
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for tm_zone member of
> struct tm" >&5
> @@ -54476,7 +54629,9 @@ $as_echo "#define _GLIBCXX_USE_STRUCT_TM_TM_ZONE
> 1" >>confdefs.h
>
>    fi
>
> +
>    CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -54485,6 +54640,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For src/c++11/shared_ptr.cc alignment.
>
>
> @@ -54494,6 +54650,9 @@ ac_compile='$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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether static
> objects can be aligned to the cacheline size" >&5
>  $as_echo_n "checking whether static objects can be aligned to the
> cacheline size... " >&6; }
> @@ -54526,6 +54685,9 @@ _ACEOF
>    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_alignas_cacheline"
> >&5
>  $as_echo "$ac_alignas_cacheline" >&6; }
>
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -54534,15 +54696,20 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For using init_priority in ios_init.cc
>
>
> +
>    ac_ext=cpp
>  ac_cpp='$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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether init_priority
> attribute is supported" >&5
>  $as_echo_n "checking whether init_priority attribute is supported... "
> >&6; }
> @@ -54577,6 +54744,9 @@ _ACEOF
>    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_init_priority" >&5
>  $as_echo "$ac_init_priority" >&6; }
>
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -54585,15 +54755,20 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For __basic_file::native_handle()
>
>
> +
>    ac_ext=cpp
>  ac_cpp='$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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether
> _get_osfhandle is defined in <io.h>" >&5
>  $as_echo_n "checking whether _get_osfhandle is defined in <io.h>... "
> >&6; }
> @@ -54635,6 +54810,9 @@ _ACEOF
>    { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_get_osfhandle" >&5
>  $as_echo "$ac_get_osfhandle" >&6; }
>
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -54643,15 +54821,20 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # For std::text_encoding
>
>
> +
>    ac_ext=cpp
>  ac_cpp='$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
>
> +  ac_save_CXXFLAGS="$CXXFLAGS"
> +  ac_save_LIBS="$LIBS"
> +
>
>    { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether nl_langinfo_l
> is defined in <langinfo.h>" >&5
>  $as_echo_n "checking whether nl_langinfo_l is defined in <langinfo.h>...
> " >&6; }
> @@ -54692,6 +54875,9 @@ _ACEOF
>
>    fi
>
> +
> +  CXXFLAGS="$ac_save_CXXFLAGS"
> +  LIBS="$ac_save_LIBS"
>    ac_ext=c
>  ac_cpp='$CPP $CPPFLAGS'
>  ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
> @@ -54700,6 +54886,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>
>
>
> +
>  # Define documentation rules conditionally.
>
>  # See if makeinfo has been installed and is modern enough
> --
> 2.49.0
>
>
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