[committed] libstdc++: Only use __builtin_sprintf if supported [PR 96083]

[Jonathan Wakely]

On 16/12/20 09:23 -0700, Martin Sebor via Libstdc++ wrote:
>On 12/16/20 8:00 AM, Jonathan Wakely via Gcc-patches wrote:
>>Clang doesn't support __builtin_sprintf, so use std::sprintf instead.
>>
>>libstdc++-v3/ChangeLog:
>>
>>	PR libstdc++/96083
>>	* include/ext/throw_allocator.h: Use __has_builtin to check for
>>	__builtin_sprintf support, and use std::sprtinf if necessary.
>>
>>Tested powerpc64le-linux. Committed to trunk.
>>
>
>I expected to see the test itself guarded by #ifdef __has_builtin
>like in <utility>.  Or is this code only [meant to be] used with
>compilers that understand __has_builtin?  (I'm mostly just curious
>here about support for other compilers like ICC, not necessarily
>pointing out a problem with the patch.)

All recent versions of Intel and Clang support __has_builtin.
(For Intel __has_builtin(__builtin_sprintf) is true, for Clang it's
false. But they both support checking it.)

The #ifdef __has_builtin in <utility> was added more than three years
ago, before GCC supported __has_builtin. So that check was there to
make the code work with GCC, not other compilers.

Now that GCC supports it, I can simplify that.