Re: [PATCH] Fix compile error due to [[noreturn]] with clang

[Guinevere Larsen <guinevere@redhat.com>]

On 10/20/24 3:00 PM, andrew@andrewoates.com wrote:
> From: Andrew Oates <andrew@andrewoates.com>
>
> Since commit d9deb60b2e9e94b532f43a7d3ddddf5ddf6dbdd3, I get the
> following compiler error when building binutils (cross-compiling) on
> macos:
>
>   CXX    remote-sim.o
> ../../gdb/remote-sim.c:334:28: error: assigning to 'void (*)(host_callback *, const char *, ...) __attribute__((noreturn))' (aka 'void (*)(host_callback_struct *, const char *, ...) __attribute__((noreturn))') from incompatible type 'void (host_callback
> *, const char *, ...)' (aka 'void (host_callback_struct *, const char *, ...)')
>        gdb_callback.error = gdb_os_error;
>                             ^~~~~~~~~~~~
> 1 error generated.
>
> This appears to be due to the mismatch between ATTRIBUTE_NORETURN and
> [[noreturn]] on gdb_os_error.  Removing ATTTRIBUTE_NORETURN on the
> declaration of host_callback::error resolves the issue.

Have you tried using ATTRIBUTE_NORETURN for gdb_os_error instead? If the 
problem is the mismatch, I would prefer that we made them match over 
removing information for the compiler.

Also, from my little knowledge in this area, this sounds like a clang 
bug. I encourage you to report it to upstream clang, or I can do it 
myself if you'd prefer.

-- 
Cheers,
Guinevere Larsen
She/Her/Hers

>
> Tested by compiling on macos both with the system clang, as well as with
> GCC 14.  With clang, remote-sim.c does not compile (per above) without
> this patch.  With GCC, it compiles with and without the patch (it
> doesn't link, but AFAICT that is unrelated).
> ---
>   include/sim/callback.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/sim/callback.h b/include/sim/callback.h
> index f69f783abac..045ac3411af 100644
> --- a/include/sim/callback.h
> +++ b/include/sim/callback.h
> @@ -129,7 +129,7 @@ struct host_callback_struct
>        In the case of gdb "exiting" means doing a longjmp back to the main
>        command loop.  */
>     void (*error) (host_callback *, const char *, ...)
> -    ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF_2;
> +    ATTRIBUTE_PRINTF_2;
>   
>     int last_errno;		/* host format */
>