[PATCH][BZ #21326] Ensure C99 and C11 interfaces are available for C++

[Florian Weimer]

On 09/22/2017 08:16 PM, Jonathan Wakely wrote:
> +#ifdef __cplusplus
> +/* This is to enable compatibility for ISO C++17.  */
> +#if __cplusplus >= 201703L
> +# define __USE_ISOC11	1
> +#endif
>   /* This is to enable compatibility for ISO C++11.

The inner #if/#endif should be indented (similar to the inner #define).

> -
> -   So far g++ does not provide a macro.  Check the temporary macro for
> -   now, too.  */
> -#if ((defined __cplusplus && __cplusplus >= 201103L)			      \
> -     || defined __GXX_EXPERIMENTAL_CXX0X__)
> +   Check the temporary macro for now, too.  */
> +#if __cplusplus >= 201103L || defined __GXX_EXPERIMENTAL_CXX0X__
>   # define __USE_ISOCXX11	1
> +# define __USE_ISOC99	1
> +#endif
>   #endif

I think there is a preexisting issue here which will trigger macro 
redefinition warnings with -Wsystem-headers.  But perhaps I'm mistaken.

Apart from that, the substance of the patch looks okay to me.

Thanks,
Florian