[PATCH] libstdc++: Fix and simplify freestanding configuration [PR103866]

Jonathan Wakely jwakely@redhat.com
Mon Jan 10 12:25:28 GMT 2022


On Fri, 7 Jan 2022 at 13:46, Jonathan Wakely via Libstdc++ <
libstdc++@gcc.gnu.org> wrote:

> Tested powerpc64le-linux and by building a mips-none-elf cross with
> --disable-hosted-libstdcxx --without-headers (which fails currently).
>
> Any objections?
>

Pushed to trunk.




>
> This fixes the --disable-hosted-libstdcxx build so that it works with
> --without-headers. Currently you need to also use --with-newlib, which
> is confusing for users who aren't actually using newlib.
>
> The AM_PROG_LIBTOOL checks are currently skipped for --with-newlib and
> --with-avrlibc builds, with this change they are also skipped when using
> --without-headers.  It would be nice if using --disable-hosted-libstdcxx
> automatically skipped those checks, but GLIBCXX_ENABLE_HOSTED comes too
> late to make the AM_PROG_LIBTOOL checks depend on $is_hosted.
>
> The checks for EOF, SEEK_CUR etc. cause the build to fail if there is no
> <stdio.h> available.  Unlike most headers, which get a HAVE_FOO_H macro,
> <stdio.h> is in autoconf's default includes, so every check tries to
> include it unconditionally. This change skips those checks for
> freestanding builds.
>
> Similarly, the checks for <stdint.h> types done by GCC_HEADER_STDINT try
> to include <stdio.h> and fail for --without-headers builds. This change
> skips the use of GCC_HEADER_STDINT for freestanding. We can probably
> stop using GCC_HEADER_STDINT entirely, since only one file uses the
> gstdint.h header that is generated, and that could easily be changed to
> use <stdint.h> instead. That can wait for stage 1.
>
> We also need to skip the GLIBCXX_CROSSCONFIG stage if --without-headers
> was used, since we don't have any of the functions it deals with.
>
> The end result of the changes above is that it should not be necessary
> for a --disable-hosted-libstdcxx --without-headers build to also use
> --with-newlib.
>
> Finally, compile libsupc++ with -ffreestanding when --without-headers is
> used, so that <stdint.h> will use <gcc-stdint.h> instead of expecting it
> to come from libc.
>
> libstdc++-v3/ChangeLog:
>
>         PR libstdc++/103866
>         * acinclude.m4 (GLIBCXX_COMPUTE_STDIO_INTEGER_CONSTANTS): Do
>         nothing for freestanding builds.
>         (GLIBCXX_ENABLE_HOSTED): Define FREESTANDING_FLAGS.
>         * configure.ac: Do not use AC_LIBTOOL_DLOPEN when configured
>         with --without-headers.  Do not use GCC_HEADER_STDINT for
>         freestanding builds.
>         * libsupc++/Makefile.am (HOSTED_CXXFLAGS): Use -ffreestanding
>         for freestanding builds.
>         * configure: Regenerate.
>         * Makefile.in: Regenerate.
>         * doc/Makefile.in: Regenerate.
>         * include/Makefile.in: Regenerate.
>         * libsupc++/Makefile.in: Regenerate.
>         * po/Makefile.in: Regenerate.
>         * python/Makefile.in: Regenerate.
>         * src/Makefile.in: Regenerate.
>         * src/c++11/Makefile.in: Regenerate.
>         * src/c++17/Makefile.in: Regenerate.
>         * src/c++20/Makefile.in: Regenerate.
>         * src/c++98/Makefile.in: Regenerate.
>         * src/filesystem/Makefile.in: Regenerate.
>         * testsuite/Makefile.in: Regenerate.
> ---
>  libstdc++-v3/Makefile.in                |  1 +
>  libstdc++-v3/acinclude.m4               |  8 ++++++
>  libstdc++-v3/configure                  | 35 ++++++++++++++++++-------
>  libstdc++-v3/configure.ac               | 10 +++++--
>  libstdc++-v3/doc/Makefile.in            |  1 +
>  libstdc++-v3/include/Makefile.in        |  1 +
>  libstdc++-v3/libsupc++/Makefile.am      |  2 +-
>  libstdc++-v3/libsupc++/Makefile.in      |  3 ++-
>  libstdc++-v3/po/Makefile.in             |  1 +
>  libstdc++-v3/python/Makefile.in         |  1 +
>  libstdc++-v3/src/Makefile.in            |  1 +
>  libstdc++-v3/src/c++11/Makefile.in      |  1 +
>  libstdc++-v3/src/c++17/Makefile.in      |  1 +
>  libstdc++-v3/src/c++20/Makefile.in      |  1 +
>  libstdc++-v3/src/c++98/Makefile.in      |  1 +
>  libstdc++-v3/src/filesystem/Makefile.in |  1 +
>  libstdc++-v3/testsuite/Makefile.in      |  1 +
>  17 files changed, 56 insertions(+), 14 deletions(-)
>
> diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
> index 635168d7e25..b770d5bcdc4 100644
> --- a/libstdc++-v3/acinclude.m4
> +++ b/libstdc++-v3/acinclude.m4
> @@ -2081,6 +2081,7 @@ dnl Compute the EOF, SEEK_CUR, and SEEK_END integer
> constants.
>  dnl
>  AC_DEFUN([GLIBCXX_COMPUTE_STDIO_INTEGER_CONSTANTS], [
>
> +if test "$is_hosted" = yes; then
>    AC_CACHE_CHECK([for the value of EOF], glibcxx_cv_stdio_eof, [
>    AC_COMPUTE_INT([glibcxx_cv_stdio_eof], [[EOF]],
>                  [#include <stdio.h>],
> @@ -2104,6 +2105,7 @@ AC_DEFUN([GLIBCXX_COMPUTE_STDIO_INTEGER_CONSTANTS], [
>    ])
>    AC_DEFINE_UNQUOTED(_GLIBCXX_STDIO_SEEK_END, $glibcxx_cv_stdio_seek_end,
>                      [Define to the value of the SEEK_END integer
> constant.])
> +fi
>  ])
>
>  dnl
> @@ -2923,12 +2925,16 @@ AC_DEFUN([GLIBCXX_ENABLE_HOSTED], [
>             enable_hosted_libstdcxx=yes
>             ;;
>       esac])
> +  freestanding_flags=
>    if test "$enable_hosted_libstdcxx" = no; then
>      AC_MSG_NOTICE([Only freestanding libraries will be built])
>      is_hosted=no
>      hosted_define=0
>      enable_abi_check=no
>      enable_libstdcxx_pch=no
> +    if test "x$with_headers" = xno; then
> +      freestanding_flags="-ffreestanding"
> +    fi
>    else
>      is_hosted=yes
>      hosted_define=1
> @@ -2936,6 +2942,8 @@ AC_DEFUN([GLIBCXX_ENABLE_HOSTED], [
>    GLIBCXX_CONDITIONAL(GLIBCXX_HOSTED, test $is_hosted = yes)
>    AC_DEFINE_UNQUOTED(_GLIBCXX_HOSTED, $hosted_define,
>      [Define to 1 if a full hosted library is built, or 0 if
> freestanding.])
> +  FREESTANDING_FLAGS="$freestanding_flags"
> +  AC_SUBST(FREESTANDING_FLAGS)
>  ])
>
>
> diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
> index 5b3c92f4bd7..827d770f444 100644
> --- a/libstdc++-v3/configure.ac
> +++ b/libstdc++-v3/configure.ac
> @@ -90,7 +90,9 @@ AC_SYS_LARGEFILE
>  GLIBCXX_CONFIGURE
>
>  # Libtool setup.
> -if test "x${with_newlib}" != "xyes" && test "x${with_avrlibc}" != "xyes";
> then
> +if test "x${with_newlib}" != "xyes" &&
> +    test "x${with_avrlibc}" != "xyes" &&
> +    test "x$with_headers" != "xno"; then
>    AC_LIBTOOL_DLOPEN
>  fi
>  AM_PROG_LIBTOOL
> @@ -351,7 +353,7 @@ else
>
>      AC_DEFINE(HAVE_ICONV)
>      AC_DEFINE(HAVE_MEMALIGN)
> -  else
> +  elif test "x$with_headers" != "xno"; then
>      GLIBCXX_CROSSCONFIG
>    fi
>
> @@ -390,7 +392,11 @@ GCC_CHECK_UNWIND_GETIPINFO
>
>  GCC_LINUX_FUTEX([AC_DEFINE(HAVE_LINUX_FUTEX, 1, [Define if futex syscall
> is available.])])
>
> +if test "$is_hosted" = yes; then
> +# TODO: remove this and change src/c++11/compatibility-atomic-c++0x.cc to
> +# use <stdint.h> instead of <gstdint.h>.
>  GCC_HEADER_STDINT(include/gstdint.h)
> +fi
>
>  GLIBCXX_ENABLE_SYMVERS([yes])
>  AC_SUBST(libtool_VERSION)
> diff --git a/libstdc++-v3/libsupc++/Makefile.am
> b/libstdc++-v3/libsupc++/Makefile.am
> index 2a69a1cf677..65b5c1a87fd 100644
> --- a/libstdc++-v3/libsupc++/Makefile.am
> +++ b/libstdc++-v3/libsupc++/Makefile.am
> @@ -139,7 +139,7 @@ atomicity.cc: ${atomicity_file}
>  # as the occasion call for it.
>  AM_CXXFLAGS = \
>         $(glibcxx_lt_pic_flag) $(glibcxx_compiler_shared_flag) \
> -       $(XTEMPLATE_FLAGS) \
> +       $(XTEMPLATE_FLAGS) $(FREESTANDING_FLAGS) \
>         $(WARN_CXXFLAGS) $(OPTIMIZE_CXXFLAGS)  $(CONFIG_CXXFLAGS)
>
>  AM_MAKEFLAGS = \
>
>


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