Re: Incompatibilities with clang.

[Paul Eggert]

Matt Sicker wrote:
> #ifndef __has_feature
> #define __has_feature(x) 0
> #endif
> #if __has_feature(c_static_assert)
> ...
> #endif

Well, obviously that won't work with anything *but* clang,
but before we fix that, the web page in question talks about
both __has_feature(c_static_assert) and __has_extension(c_static_assert).
What's the difference, and why should we care?  Also, can we use just
one of those two and not worry about __has_feature(cxx_static_assert)
and __has_extension(cxx_static_assert), even when compiling in C++
mode?  That's the sort of thing that I was talking about
when I wrote that the documentation was unclear.

This isn't all that high-priority, since gnulib currently *is*
compatible with clang (despite the Subject: line); it's just
that compile-time checking is better with GCC than with Clang
in some cases.