[Mesa-dev] [PATCH v3 1/2] configure+mesa/st: unify check for -std=c++11 support and enable accordingly

[Emil Velikov]

Hi Gert,

On 19 September 2017 at 12:35, Gert Wollny <gw.fossdev at gmail.com> wrote:
> Unify the CXX feature tests for C++11 support that is required for SWR,
> clover, and mesa/st/tests.
>
Surely we'll have capable compiler in 90+% of the time, still asking
for C++11 for single test is an overkill.
Then again, let's get this sorted.

> Instead of using a custom made test (SWR) or testing for the gcc version
> (clover), use ax_cxx_compile_stdcxx.m4, modified to return the CXX flags
> used to enable c++11, to test for C++11 support and apply the obtained
> flag to the according modules.
>
> If c++11 support is missing fail configuration when clover or swr is
> requested, and disable compiling and running the mesa/st tests.
>
> This patch adds consistency for future compilers, since the flag -std=c++11
> will not be forced if C++11 features are enabled by default, like e.g. with
> g++ >= 6 that defaults to c++14.
>
> Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=102665
s/Fixes/Bugzilla/

> ---
>  .travis.yml                                   |   1 +
Unrelated/undocumented change?

>  configure.ac                                  |  13 +-
>  m4/ax_cxx_compile_stdcxx.m4                   | 987 ++++++++++++++++++++++++++
Please don't add custom m4 unless absolutely needed.

> --- a/configure.ac
> +++ b/configure.ac
> @@ -301,8 +301,12 @@ AX_CHECK_COMPILE_FLAG([-Wall],                                 [CXXFLAGS="$CXXFL
>  AX_CHECK_COMPILE_FLAG([-fno-math-errno],                       [CXXFLAGS="$CXXFLAGS -fno-math-errno"])
>  AX_CHECK_COMPILE_FLAG([-fno-trapping-math],                    [CXXFLAGS="$CXXFLAGS -fno-trapping-math"])
>  AX_CHECK_COMPILE_FLAG([-fvisibility=hidden],                   [VISIBILITY_CXXFLAGS="-fvisibility=hidden"])
> +AX_CXX_COMPILE_STDCXX(11, noext, optional)
> +
>  AC_LANG_POP([C++])
>
> +AM_CONDITIONAL(HAVE_STD_CXX11, test "x$HAVE_CXX11" = "x1")
> +
>  # Flags to help ensure that certain portions of the code -- and only those
>  # portions -- can be built with MSVC:
>  # - src/util, src/gallium/auxiliary, rc/gallium/drivers/llvmpipe, and
> @@ -2234,9 +2238,7 @@ if test "x$enable_opencl" = xyes; then
>          AC_MSG_ERROR([cannot enable OpenCL without Gallium])
>      fi
>
> -    if test $GCC_VERSION_MAJOR -lt 4 -o $GCC_VERSION_MAJOR -eq 4 -a $GCC_VERSION_MINOR -lt 7; then
> -        AC_MSG_ERROR([gcc >= 4.7 is required to build clover])
> -    fi
> +    AX_CXX_COMPILE_STDCXX(11, noext, mandatory)
>
Why check again - you already know the result.

>      if test "x$have_libclc" = xno; then
>          AC_MSG_ERROR([pkg-config cannot find libclc.pc which is required to build clover.
> @@ -2518,10 +2520,7 @@ if test -n "$with_gallium_drivers"; then
>          xswr)
>              llvm_require_version $LLVM_REQUIRED_SWR "swr"
>
> -            swr_require_cxx_feature_flags "C++11" "__cplusplus >= 201103L" \
> -                ",-std=c++11" \
> -                SWR_CXX11_CXXFLAGS
> -            AC_SUBST([SWR_CXX11_CXXFLAGS])
> +           AX_CXX_COMPILE_STDCXX(11, noext, mandatory)
>
Ditto.

You'd want to update the other SWR_CXX11_CXXFLAGS reference further down.

> --- a/src/gallium/drivers/swr/Makefile.am
> +++ b/src/gallium/drivers/swr/Makefile.am
> @@ -22,7 +22,7 @@
>  include Makefile.sources
>  include $(top_srcdir)/src/gallium/Automake.inc
>
> -AM_CXXFLAGS = $(GALLIUM_DRIVER_CFLAGS) $(SWR_CXX11_CXXFLAGS)
> +AM_CXXFLAGS = $(GALLIUM_DRIVER_CFLAGS) $(CXX11_FLAGS)
>
>  noinst_LTLIBRARIES = libmesaswr.la
>
> @@ -39,7 +39,7 @@ COMMON_CXXFLAGS = \
>         -fno-strict-aliasing \
>         $(GALLIUM_DRIVER_CFLAGS) \
>         $(LLVM_CXXFLAGS) \
> -       $(SWR_CXX11_CXXFLAGS) \
> +       $(CXX11_FLAGS) \
>         -I$(builddir)/rasterizer/codegen \
>         -I$(builddir)/rasterizer/core \
>         -I$(builddir)/rasterizer/jitter \
> diff --git a/src/gallium/state_trackers/clover/Makefile.am b/src/gallium/state_trackers/clover/Makefile.am
> index 321393536d..35b43b380c 100644
> --- a/src/gallium/state_trackers/clover/Makefile.am
> +++ b/src/gallium/state_trackers/clover/Makefile.am
> @@ -31,14 +31,14 @@ endif
>  noinst_LTLIBRARIES = libclover.la libcltgsi.la libclllvm.la
>
>  libcltgsi_la_CXXFLAGS = \
> -       -std=c++11 \
> +       ${CXX11_FLAGS} \
Please stay consistent through the file 's/{/(';'s/}/)'

Thanks
Emil