[patch] Test setrlimit with c++ in libstdc++/configure

[Jonathan Wakely]

On 16/12/19 14:51 +0100, Jérôme Lambourg wrote:
>Hello,
>
>In libstdc++, the test for the presence of setrlimit on the target is currently
>performed in C as opposed to the other similar tests there. This leads on only a
>warning being issued during configure as opposed to the expected error, and thus
>improper definition of _GLIBCXX_RES_LIMITS.
>
>This happens in particular on VxWorks where the standard header files are
>available and the "struct rlimit" type definition is there. During configure,
>only the setrlimit function prototype is missing so the compilation in C only
>yield warnings and the test passes.
>
>This patch fixes that by switching to C++ before testing setrlimit. It was
>implemented first on gcc-8 for our internal needs, then ported to gcc-9 and now
>mainline for contribution.
>
>This change shouldn't impact targets where setrlimit is actually defined. I
>tested the change on Linux to check that the result of the configure stage is
>not changed by this patch.
>
>Best regards,
>Jerome
>
>
>2019-12-16  Corentin Gay  <gay@adacore.com>
>           Jerome Lambourg  <lambourg@adacore.com>
>
>libstdc++
>	* acinclude.m4 (GLIBCXX_CHECK_SETRLIMIT): Test with AC_LANG_CPLUSPLUS.
>	* configure: Regenerate.
>

OK for trunk, thanks.

>diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
>index 016b0c583d0..0c58d722988 100644
>--- a/libstdc++-v3/acinclude.m4
>+++ b/libstdc++-v3/acinclude.m4
>@@ -316,6 +316,8 @@ AC_DEFUN([GLIBCXX_CHECK_SETRLIMIT_ancilliary], [
> ])
>
> AC_DEFUN([GLIBCXX_CHECK_SETRLIMIT], [
>+  AC_LANG_SAVE
>+  AC_LANG_CPLUSPLUS
>   setrlimit_have_headers=yes
>   AC_CHECK_HEADERS(unistd.h sys/time.h sys/resource.h,
>                   [],
>@@ -352,6 +354,7 @@ AC_DEFUN([GLIBCXX_CHECK_SETRLIMIT], [
>   else
>     ac_res_limits=no
>   fi
>+  AC_LANG_RESTORE
>   AC_MSG_RESULT($ac_res_limits)
> ])
>
>