https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90992
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #4)
> This suppresses the second warning if the first is suppressed:
>
> --- a/gcc/cp/except.c
> +++ b/gcc/cp/except.c
> @@ -1158,11 +1158,11 @@ maybe_noexcept_warning (tree fn)
> {
> if (TREE_NOTHROW (fn))
> {
> - warning (OPT_Wnoexcept, "noexcept-expression evaluates to %<false%> "
> - "because of a call to %qD", fn);
> - warning_at (DECL_SOURCE_LOCATION (fn), OPT_Wnoexcept,
> - "but %qD does not throw; perhaps "
> - "it should be declared %<noexcept%>", fn);
> + if (warning (OPT_Wnoexcept, "noexcept-expression evaluates to
> %<false%> "
> + "because of a call to %qD", fn))
> + warning_at (DECL_SOURCE_LOCATION (fn), OPT_Wnoexcept,
> + "but %qD does not throw; perhaps "
> + "it should be declared %<noexcept%>", fn);
> }
> }
>
>
>
> And this makes the first warning depend on whether the second one is in a
> system header:
>
> --- a/gcc/cp/except.c
> +++ b/gcc/cp/except.c
> @@ -1158,11 +1158,20 @@ maybe_noexcept_warning (tree fn)
> {
> if (TREE_NOTHROW (fn))
> {
> + location_t loc = DECL_SOURCE_LOCATION (fn);
> +
> + const bool warn_in_system_headers = global_dc->dc_warn_system_headers;
> + if (in_system_header_at (input_location) && !in_system_header_at (loc)
> + && !warn_in_system_headers)
> + global_dc->dc_warn_system_headers = 1;
> warning (OPT_Wnoexcept, "noexcept-expression evaluates to %<false%> "
> "because of a call to %qD", fn);
> - warning_at (DECL_SOURCE_LOCATION (fn), OPT_Wnoexcept,
> + warning_at (loc, OPT_Wnoexcept,
> "but %qD does not throw; perhaps "
> "it should be declared %<noexcept%>", fn);
> + if (in_system_header_at (input_location) && !in_system_header_at (loc)
> + && !warn_in_system_headers)
> + global_dc->dc_warn_system_headers = 0;
> }
> }
>
>
> I don't know which of these is preferable, because I'm not sure if the point
> of the warning is to suggest changing Automatic, or the code in the system
> header.
I'd say the second looks insufficient, system headers vs. non-system headers is
just one of the reasons why a warning might be disabled, it can be #pragma GCC
diagnostic ignored too. Purely from diagnostic POV, I'd say it should be
auto_diagnostic_group d;
if (warning (OPT_Wnoexcept, "...", fn))
inform (loc, "...", fn);
Have you posted the patch?
The warning has been added by Jason in r160842.
