c, c++: Allow ignoring -Winit-self through pragmas [PR105593]

As mentioned in the PR, various x86 intrinsics need to return
an uninitialized vector.  Currently they use self initialization
to avoid -Wuninitialized warnings, which works fine in C, but
doesn't work in C++ where -Winit-self is enabled in -Wall.
We don't have an attribute to mark a variable as knowingly
uninitialized (the uninitialized attribute exists but means
something else, only in the -ftrivial-auto-var-init context),
and trying to suppress either -Wuninitialized or -Winit-self
inside of the _mm_undefined_ps etc. intrinsic definitions
doesn't work, one needs to currently disable through pragmas
-Wuninitialized warning at the point where _mm_undefined_ps etc.
result is actually used, but that goes against the intent of
those intrinsics.

The -Winit-self warning option actually doesn't do any warning,
all we do is record a suppression for -Winit-self if !warn_init_self
on the decl definition and later look that up in uninit pass.

The following patch changes those !warn_init_self tests which
are true only based on the command line option setting, not based
on GCC diagnostic pragma overrides to
!warning_enabled_at (DECL_SOURCE_LOCATION (decl), OPT_Winit_self)
such that it takes them into account.

2023-01-16  Jakub Jelinek  <jakub@redhat.com>

	PR c++/105593
gcc/c/
	* c-parser.cc (c_parser_initializer): Check warning_enabled_at
	at the DECL_SOURCE_LOCATION (decl) for OPT_Winit_self instead
	of warn_init_self.
gcc/cp/
	* decl.cc (cp_finish_decl): Check warning_enabled_at
	at the DECL_SOURCE_LOCATION (decl) for OPT_Winit_self instead
	of warn_init_self.
gcc/testsuite/
	* c-c++-common/Winit-self3.c: New test.
	* c-c++-common/Winit-self4.c: New test.
	* c-c++-common/Winit-self5.c: New test.

1 files changed, 1 insertions, 1 deletions

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 66e7d9f..6b1c4a2 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -8407,7 +8407,7 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
       if (!DECL_EXTERNAL (decl)
 	  && !TREE_STATIC (decl)
 	  && decl == tree_strip_any_location_wrapper (init)
-	  && !warn_init_self)
+	  && !warning_enabled_at (DECL_SOURCE_LOCATION (decl), OPT_Winit_self))
 	suppress_warning (decl, OPT_Winit_self);
     }