[Mesa-dev] [PATCH] configure: simplify visibility compiler flag detection

[Matt Turner]

On Sun, Mar 1, 2015 at 6:09 AM, Marc Dietrich <marvin24 at gmx.de> wrote:
> This patch simplifies the visibility compiler flag detection in configure and
> makes it more generic to also support compilers other than gcc.

This simplification relies on the assumption that compilers support
-fvisibility=... if and only if they support
attribute(visibility("...")).

I guess that might be the case, but the logic doesn't seem very sound.

Is the 'if test "x$GCC" = xyes; then' test actually rejecting clang?
It doesn't seem so, since above there's a 'if test "x$GCC" = xyes -a
"x$acv_mesa_CLANG" = xno; then'

So, I guess it looks to me like we already support visibility
detection for !gcc.

>
> Cc: Emil Velikov <emil.l.velikov at gmail.com>
> Signed-off-by: Marc Dietrich <marvin24 at gmx.de>
>
> ---
>  configure.ac | 32 +++++++-------------------------
>  1 file changed, 7 insertions(+), 25 deletions(-)
>
> diff --git a/configure.ac b/configure.ac
> index 5fbb7bc..7565c0c 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -189,6 +189,7 @@ AX_GCC_FUNC_ATTRIBUTE([flatten])
>  AX_GCC_FUNC_ATTRIBUTE([format])
>  AX_GCC_FUNC_ATTRIBUTE([malloc])
>  AX_GCC_FUNC_ATTRIBUTE([packed])
> +AX_GCC_FUNC_ATTRIBUTE([visibility])
>
>  AM_CONDITIONAL([GEN_ASM_OFFSETS], test "x$GEN_ASM_OFFSETS" = xyes)
>
> @@ -223,6 +224,12 @@ cygwin*)
>      ;;
>  esac
>
> +# Enable -fvisibility=hidden if using a compiler that supports it
> +if test "x${ax_cv_have_func_attribute_visibility}" = xyes; then
> +       VISIBILITY_CFLAGS="-fvisibility=hidden"
> +       VISIBILITY_CXXFLAGS="-fvisibility=hidden"

Indent these the same amount as elsewhere.

> +fi
> +
>  dnl Add flags for gcc and g++
>  if test "x$GCC" = xyes; then
>      CFLAGS="$CFLAGS -Wall"
> @@ -245,18 +252,6 @@ if test "x$GCC" = xyes; then
>                    AC_MSG_RESULT([yes]),
>                    [CFLAGS="$save_CFLAGS -Wmissing-prototypes";
>                     AC_MSG_RESULT([no])]);
> -
> -    # Enable -fvisibility=hidden if using a gcc that supports it
> -    save_CFLAGS="$CFLAGS"
> -    AC_MSG_CHECKING([whether $CC supports -fvisibility=hidden])
> -    VISIBILITY_CFLAGS="-fvisibility=hidden"
> -    CFLAGS="$CFLAGS $VISIBILITY_CFLAGS"
> -    AC_LINK_IFELSE([AC_LANG_PROGRAM()], AC_MSG_RESULT([yes]),
> -                  [VISIBILITY_CFLAGS=""; AC_MSG_RESULT([no])]);
> -
> -    # Restore CFLAGS; VISIBILITY_CFLAGS are added to it where needed.
> -    CFLAGS=$save_CFLAGS
> -
>      # Work around aliasing bugs - developers should comment this out
>      CFLAGS="$CFLAGS -fno-strict-aliasing"
>
> @@ -267,19 +262,6 @@ fi
>  if test "x$GXX" = xyes; then
>      CXXFLAGS="$CXXFLAGS -Wall"
>
> -    # Enable -fvisibility=hidden if using a gcc that supports it
> -    save_CXXFLAGS="$CXXFLAGS"
> -    AC_MSG_CHECKING([whether $CXX supports -fvisibility=hidden])
> -    VISIBILITY_CXXFLAGS="-fvisibility=hidden"
> -    CXXFLAGS="$CXXFLAGS $VISIBILITY_CXXFLAGS"
> -    AC_LANG_PUSH([C++])
> -    AC_LINK_IFELSE([AC_LANG_PROGRAM()], AC_MSG_RESULT([yes]),
> -                  [VISIBILITY_CXXFLAGS="" ; AC_MSG_RESULT([no])]);
> -    AC_LANG_POP([C++])
> -
> -    # Restore CXXFLAGS; VISIBILITY_CXXFLAGS are added to it where needed.
> -    CXXFLAGS=$save_CXXFLAGS
> -
>      # Work around aliasing bugs - developers should comment this out
>      CXXFLAGS="$CXXFLAGS -fno-strict-aliasing"
>
> --
> 2.3.0
>
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/mesa-dev