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Date: Fri, 14 Jun 2019 09:50:45 -0700
From: Matthew Maurer <mmaurer@...gle.com>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] Use __attribute__((noreturn)) for function pointer
Done.
On Fri, Jun 14, 2019 at 9:47 AM Rich Felker <dalias@...c.org> wrote:
> On Fri, Jun 14, 2019 at 09:42:09AM -0700, Matthew Maurer wrote:
> > _Noreturn doesn't actually exist in C99 - that's a C11ism. Even in C11,
> it
> > cannot be used on a function pointer type.
> > __attribute__((noreturn)) is a GNU C extension (which we're allowed to
> use,
> > unlike C11), and is allowed to be placed on function pointer types.
>
> > From adeca3acc1e4c1b727e8524542c201b436ba8a5b Mon Sep 17 00:00:00 2001
> > From: Matthew Maurer <mmaurer@...gle.com>
> > Date: Thu, 13 Jun 2019 12:33:38 -0700
> > Subject: [PATCH] Use __attribute__((noreturn)) for function pointer
> >
> > _Noreturn is a C11 construct, and may only be used at the site of a
> > function definition.
> > __attribute__((noreturn)) is a GNU C extension which may be used on
> > function pointers.
> > GCC with any standard permits _Noreturn in the position it's used
> > (likely because it implements it in terms of attribute noreturn), but
> > Clang will reject it for any standard past C11, and warn pre-C11.
> >
> > Musl is written in C99 with GNU C extensions, so
> > __attribute__((noreturn)) is both more correct in that sense and allows
> > us to compile with Clang set to higher language standards.
> > ---
> > src/internal/dynlink.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/src/internal/dynlink.h b/src/internal/dynlink.h
> > index cbe0a6fe..d2bf6b41 100644
> > --- a/src/internal/dynlink.h
> > +++ b/src/internal/dynlink.h
> > @@ -95,7 +95,7 @@ struct fdpic_dummy_loadmap {
> > #define DYN_CNT 32
> >
> > typedef void (*stage2_func)(unsigned char *, size_t *);
> > -typedef _Noreturn void (*stage3_func)(size_t *);
> > +typedef __attribute__((noreturn)) void (*stage3_func)(size_t *);
> >
> > hidden void *__dlsym(void *restrict, const char *restrict, void
> *restrict);
> >
> > --
> > 2.22.0.410.gd8fdbe21b5-goog
> >
>
> Just remove it. There's no sense having nonstandard C here for
> something that's completely inconsequential. It wasn't important, and
> probably the only reason I wrote it was wrongly thinking the function
> pointer type had to match the _Noreturn of the function definition.
>
> Rich
>
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View attachment "0001-Do-not-use-_Noreturn-for-a-function-pointer.patch" of type "text/x-patch" (866 bytes)
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