RFC: Add _GLIBCXX_NOEXCEPT_C macro for conditional noexcept

[Daniel Krügler]

2015-06-26 12:33 GMT+02:00 Jonathan Wakely <jwakely@redhat.com>:
> I keep considering making this change:
>
> --- a/libstdc++-v3/include/bits/c++config
> +++ b/libstdc++-v3/include/bits/c++config
> @@ -117,10 +117,12 @@
> #  define _GLIBCXX_NOEXCEPT noexcept
> #  define _GLIBCXX_USE_NOEXCEPT noexcept
> #  define _GLIBCXX_THROW(_EXC)
> +#  define _GLIBCXX_NOEXCEPT_C(_CONSTANT) noexcept(_CONSTANT)
> # else
> #  define _GLIBCXX_NOEXCEPT
> #  define _GLIBCXX_USE_NOEXCEPT throw()
> #  define _GLIBCXX_THROW(_EXC) throw(_EXC)
> +#  define _GLIBCXX_NOEXCEPT_C(_CONSTANT)
> # endif
> #endif
>
>
> It would allow code like this:
>
>    basic_string()
>  #if __cplusplus >= 201103L
>    noexcept(is_nothrow_default_constructible<_Alloc>::value)
>  #endif
>
> to be replaced with this:
>
>    basic_string()
>    _GLIBCXX_NOEXCEPT_C(is_nothrow_default_constructible<_Alloc>::value)
>
> But I can't decide if that's really an improvement.
>
> Does anyone else have an opinion?

To me, your change suggestion looks like a real improvement.

- Daniel