On Sat, 11 Dec 2021, 10:56 Olivier Hainque via Libstdc++, <
libstd...@gcc.gnu.org> wrote:
> (Thanks for your feedback Jonathan)
>
> > On 10 Dec 2021, at 19:24, Jonathan Wakely <jwak...@redhat.com> wrote:
> >
> > I'm curious why _GLIBCXX_USE_C99_CTYPE_TR1 is not defined if VxWorks
> > has isblank, the configure check is:
>
> Oh, hmm, very good point. The reason was that the definition
> of isblank is conditioned on _C99/_HAS_C9X as well, so the need
> for which we had introduced the definition in os_defines.h
> would better be generalized.
>
> * config/vxworks.h (VXWORKS_OS_CPP_BUILTINS): Define
> _C99 for C++.
>
> --- a/gcc/config/vxworks.h
> +++ b/gcc/config/vxworks.h
> @@ -328,6 +328,10 @@ extern void vxworks_asm_out_destructor (rtx symbol,
> int priority);
> if (!flag_isoc99 && !c_dialect_cxx()) \
> builtin_define ("_ALLOW_KEYWORD_MACROS"); \
> } \
> + /* C++ support relies on C99 features. Make sure they are \
> + exposed by the system headers. */ \
> + if (c_dialect_cxx()) \
> + builtin_define("_C99"); \
> } \
> while (0)
>
>
> Works with the two libstdc++ changes reverted, and gives
> "configure" a better view of what's there.
>
> Makes sense?
Yes. I can't approve patches outside libstdc++, but that looks definitely
correct for C++11 and later, because C++11 incorporates the whole C99
library by reference. So if that macro is needed to get the C99 library
(because the vxworks libc doesn't check the__cplusplus macro and enable C99
features that way), then I agree _C99 should be defined for C++11. Defining
it for C++11 is sufficient to solve the isblank problem, because
std::isblank is only declared for C++11 and later. (std::tr1::isblank is
declared for C++98 if the C library supports it, but nobody really cares
about TR1 nowadays, and probably hardly anybody cares about C++98).
Defining _C99 is not strictly correct for C++98 mode, because C++98
incorporates the C89 library by reference. But as you noted in the earlier
patch, libstdc++ likes to have full C99 facilities available even for C++98
mode (so it can use them for std::tr1 features, among other things). So I
think defining it even for C++98 is fine too.
