On Wed, 6 Dec 2023, Jakub Jelinek wrote:
> Hi!
>
> When libgcc is being built in --disable-tls configuration or on
> a target without native TLS support, one gets annoying warnings:
> ../../../../libgcc/emutls.c:61:7: warning: conflicting types for built-in
> function ?__emutls_get_address?; expected ?void *(void *)?
> [-Wbuiltin-declaration-mismatch]
> 61 | void *__emutls_get_address (struct __emutls_object *);
> | ^~~~~~~~~~~~~~~~~~~~
> ../../../../libgcc/emutls.c:63:6: warning: conflicting types for built-in
> function ?__emutls_register_common?; expected ?void(void *, unsigned int,
> unsigned int, void *)? [-Wbuiltin-declaration-mismatch]
> 63 | void __emutls_register_common (struct __emutls_object *, word, word,
> void *);
> | ^~~~~~~~~~~~~~~~~~~~~~~~
> ../../../../libgcc/emutls.c:140:1: warning: conflicting types for built-in
> function ?__emutls_get_address?; expected ?void *(void *)?
> [-Wbuiltin-declaration-mismatch]
> 140 | __emutls_get_address (struct __emutls_object *obj)
> | ^~~~~~~~~~~~~~~~~~~~
> ../../../../libgcc/emutls.c:204:1: warning: conflicting types for built-in
> function ?__emutls_register_common?; expected ?void(void *, unsigned int,
> unsigned int, void *)? [-Wbuiltin-declaration-mismatch]
> 204 | __emutls_register_common (struct __emutls_object *obj,
> | ^~~~~~~~~~~~~~~~~~~~~~~~
> The thing is that in that case __emutls_get_address and
> __emutls_register_common are builtins, and are declared with void *
> arguments rather than struct __emutls_object *.
> Now, struct __emutls_object is a type private to libgcc/emutls.c and the
> middle-end creates on demand when calling the builtins a similar structure
> (with small differences, like not having the union in there).
>
> We have a precedent for this e.g. for fprintf or strftime builtins where
> the builtins are created with magic fileptr_type_node or
> const_tm_ptr_type_node
> types and then match it with user definition of pointers to some structure,
> but I think for this case users should never define these functions
> themselves nor call them and having special types for them in the compiler
> would mean extra compile time spent during compiler initialization and more
> GC data, so I think it is better to keep the compiler as is.
>
> On the library side, there is an option to just follow what the
> compiler is doing and do
> EMUTLS_ATTR void
> -__emutls_register_common (struct __emutls_object *obj,
> +__emutls_register_common (void *xobj,
> word size, word align, void *templ)
> {
> + struct __emutls_object *obj = (struct __emutls_object *) xobj;
> but that will make e.g. libabigail complain about ABI change in libgcc.
>
> So, the patch just turns the warning off.
>
> Tested on x86_64-linux with --disable-tls, ok for trunk?
Works for me.
Richard.
> 2023-12-06 Thomas Schwinge <tho...@codesourcery.com>
> Jakub Jelinek <ja...@redhat.com>
>
> PR libgcc/109289
> * emutls.c: Add GCC diagnostic ignored "-Wbuiltin-declaration-mismatch"
> pragma.
>
> --- libgcc/emutls.c.jj 2023-01-16 11:52:16.780723793 +0100
> +++ libgcc/emutls.c 2023-12-06 10:49:46.438060090 +0100
> @@ -57,6 +57,14 @@ struct __emutls_array
> # define EMUTLS_ATTR
> #endif
>
> +/* __emutls_get_address and __emutls_register_common are registered as
> + builtins, but the compiler struct __emutls_object doesn't have
> + a union in there and is only created when actually needed for
> + the calls to the builtins, so the builtins are created with void *
> + arguments rather than struct __emutls_object *. Avoid
> + -Wbuiltin-declaration-mismatch warnings. */
> +#pragma GCC diagnostic ignored "-Wbuiltin-declaration-mismatch"
> +
> EMUTLS_ATTR
> void *__emutls_get_address (struct __emutls_object *);
> EMUTLS_ATTR
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
