Re: [wwwdocs] Porting-to-14: Mention new pragma GCC Target behavior

[Jakub Jelinek <jakub@redhat.com>]

On Thu, Apr 25, 2024 at 02:34:22PM +0200, Martin Jambor wrote:
> when looking at a package build issue with GCC 14, Michal Jireš noted a
> different behavior of pragma GCC Target.  This snippet tries to describe
> the gist of the problem.  I have left it in the C section even though it
> is not really C specific, but could not think of a good name for a new
> section for it.  Ideas (and any other suggestions for improvements)
> welcome, of course.

The change was more subtle.
We used to define/undefine the ISA macros in C in GCC 13 and older as well,
but only when using integrated preprocessor during compilation,
so it didn't work that way with -save-temps or separate -E and -S/-c
steps.
While in C++ it behaved as if the define/undefines aren't done at all
(they were done, but after preprocessing/lexing everything, so didn't
affect anything).
In GCC 14, it behaves in C++ the same as in C in older versions, and
additionally they are defined/undefined also when using separate
preprocessing, in both C and C++.

	Jakub