[PATCH] libcpp: Use [[likely]] conditionally

[Marek Polacek]

On Tue, Nov 23, 2021 at 04:26:19PM +0100, Christophe LYON via Gcc-patches wrote:
> Hi!
> 
> On 23/11/2021 01:26, Jeff Law via Gcc-patches wrote:
> > 
> > 
> > On 11/22/2021 10:22 AM, Marek Polacek via Gcc-patches wrote:
> > > Let's hide [[likely]] behind a macro, to suppress warnings if the
> > > compiler doesn't support it.
> > > 
> > > Co-authored-by: Jonathan Wakely <jwakely@redhat.com>
> > > 
> > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > > 
> > >     PR preprocessor/103355
> > > 
> > > libcpp/ChangeLog:
> > > 
> > >     * lex.c: Use ATTR_LIKELY instead of [[likely]].
> > >     * system.h (ATTR_LIKELY): Define.
> > OK
> > jeff
> 
> 
> This patch breaks the build when the host compiler is gcc-4.8.5, because
> __has_cpp_attribute is not defined.
 
Ah, of course.

> Is this small patch OK with a proper ChangeLog?

Yes, please.

> diff --git a/libcpp/system.h b/libcpp/system.h
> index f6fc583ab80..b78ab813d2f 100644
> --- a/libcpp/system.h
> +++ b/libcpp/system.h
> @@ -430,6 +430,8 @@ extern void fancy_abort (const char *, int, const char
> *) ATTRIBUTE_NORETURN;
>  # else
>  #  define ATTR_LIKELY
>  # endif
> +#else
> +# define ATTR_LIKELY
>  #endif
> 
>  /* Poison identifiers we do not want to use.  */
> 
> 
> Thanks,
> 
> 
> Christophe
> 
> 
> 

Marek