* [PATCH] Use __attribute__((noreturn)) for function pointer @ 2019-06-14 16:42 Matthew Maurer 2019-06-14 16:47 ` Rich Felker 0 siblings, 1 reply; 4+ messages in thread From: Matthew Maurer @ 2019-06-14 16:42 UTC (permalink / raw) To: musl [-- Attachment #1.1: Type: text/plain, Size: 262 bytes --] _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. [-- Attachment #1.2: Type: text/html, Size: 306 bytes --] [-- Attachment #2: 0001-Use-__attribute__-noreturn-for-function-pointer.patch --] [-- Type: text/x-patch, Size: 1369 bytes --] From adeca3acc1e4c1b727e8524542c201b436ba8a5b Mon Sep 17 00:00:00 2001 From: Matthew Maurer <mmaurer@google.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 ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Use __attribute__((noreturn)) for function pointer 2019-06-14 16:42 [PATCH] Use __attribute__((noreturn)) for function pointer Matthew Maurer @ 2019-06-14 16:47 ` Rich Felker 2019-06-14 16:50 ` Matthew Maurer 0 siblings, 1 reply; 4+ messages in thread From: Rich Felker @ 2019-06-14 16:47 UTC (permalink / raw) To: musl 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@google.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 ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Use __attribute__((noreturn)) for function pointer 2019-06-14 16:47 ` Rich Felker @ 2019-06-14 16:50 ` Matthew Maurer 2019-06-25 22:58 ` Rich Felker 0 siblings, 1 reply; 4+ messages in thread From: Matthew Maurer @ 2019-06-14 16:50 UTC (permalink / raw) To: musl [-- Attachment #1.1: Type: text/plain, Size: 2223 bytes --] Done. On Fri, Jun 14, 2019 at 9:47 AM Rich Felker <dalias@libc.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@google.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 > [-- Attachment #1.2: Type: text/html, Size: 2869 bytes --] [-- Attachment #2: 0001-Do-not-use-_Noreturn-for-a-function-pointer.patch --] [-- Type: text/x-patch, Size: 866 bytes --] From f31e064e7b2175e5a20552b6b2a627f5411d9b9f Mon Sep 17 00:00:00 2001 From: Matthew Maurer <mmaurer@google.com> Date: Thu, 13 Jun 2019 12:33:38 -0700 Subject: [PATCH] Do not use _Noreturn for a function pointer _Noreturn is a C11 construct, and may only be used at the site of a function definition. --- 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..165bbedb 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 void (*stage3_func)(size_t *); hidden void *__dlsym(void *restrict, const char *restrict, void *restrict); -- 2.22.0.410.gd8fdbe21b5-goog ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Use __attribute__((noreturn)) for function pointer 2019-06-14 16:50 ` Matthew Maurer @ 2019-06-25 22:58 ` Rich Felker 0 siblings, 0 replies; 4+ messages in thread From: Rich Felker @ 2019-06-25 22:58 UTC (permalink / raw) To: musl On Fri, Jun 14, 2019 at 09:50:45AM -0700, Matthew Maurer wrote: > Done. > > On Fri, Jun 14, 2019 at 9:47 AM Rich Felker <dalias@libc.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@google.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. > From f31e064e7b2175e5a20552b6b2a627f5411d9b9f Mon Sep 17 00:00:00 2001 > From: Matthew Maurer <mmaurer@google.com> > Date: Thu, 13 Jun 2019 12:33:38 -0700 > Subject: [PATCH] Do not use _Noreturn for a function pointer > > _Noreturn is a C11 construct, and may only be used at the site of a > function definition. > --- > 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..165bbedb 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 void (*stage3_func)(size_t *); > > hidden void *__dlsym(void *restrict, const char *restrict, void *restrict); > > -- > 2.22.0.410.gd8fdbe21b5-goog > I've had this in my local tree for a while, but hadn't built it (didn't think I had to), and noticed that removing the _Noreturn from the type but not from __dls2b and __dls3 caused warnings (errors with my local -Werror) for "_Noreturn function returns". So I'm amending this to also remove the _Noreturn from the definitions of these functions, since it serves no purpose anyway. Now I think the only remaining uses of _Noreturn are on public interfaces that are really supposed to be _Noreturn. Rich ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-06-25 22:58 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2019-06-14 16:42 [PATCH] Use __attribute__((noreturn)) for function pointer Matthew Maurer 2019-06-14 16:47 ` Rich Felker 2019-06-14 16:50 ` Matthew Maurer 2019-06-25 22:58 ` Rich Felker
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