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[2603:7000:9a00:2ec6::1db4]) by smtp.gmail.com with ESMTPSA id q5-20020a37f705000000b006fab416015csm12606651qkj.25.2023.01.13.05.48.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Jan 2023 05:48:22 -0800 (PST) Date: Fri, 13 Jan 2023 08:48:20 -0500 From: Marek Polacek To: Jason Merrill Cc: Jakub Jelinek , "Joseph S. Myers" , gcc-patches@gcc.gnu.org Subject: Re: [PATCH] c, c++: Allow ignoring -Winit-self through pragmas [PR105593] Message-ID: References: <6872691a-ee0a-d75b-2d03-684538fc8a1e@redhat.com> MIME-Version: 1.0 In-Reply-To: <6872691a-ee0a-d75b-2d03-684538fc8a1e@redhat.com> User-Agent: Mutt/2.2.9 (2022-11-12) X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-5.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Thu, Jan 12, 2023 at 09:49:56PM -0500, Jason Merrill wrote: > On 1/12/23 19:32, Jakub Jelinek wrote: > > Hi! > > > > 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. > > > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? > > OK on Monday if the C maintainers don't comment. The C changes LGTM, thanks. > > Will post incremental patch for the intrinsic headers. > > > > 2023-01-13 Jakub Jelinek > > > > 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. > > > > --- gcc/c/c-parser.cc.jj 2023-01-11 22:18:25.560492345 +0100 > > +++ gcc/c/c-parser.cc 2023-01-12 15:30:10.460233783 +0100 > > @@ -5701,7 +5701,7 @@ c_parser_initializer (c_parser *parser, > > && !DECL_EXTERNAL (decl) > > && !TREE_STATIC (decl) > > && ret.value == decl > > - && !warn_init_self) > > + && !warning_enabled_at (DECL_SOURCE_LOCATION (decl), OPT_Winit_self)) > > suppress_warning (decl, OPT_Winit_self); > > if (TREE_CODE (ret.value) != STRING_CST > > && (TREE_CODE (ret.value) != COMPOUND_LITERAL_EXPR > > --- gcc/cp/decl.cc.jj 2023-01-04 18:42:24.597997547 +0100 > > +++ gcc/cp/decl.cc 2023-01-12 15:26:01.257817526 +0100 > > @@ -8407,7 +8407,7 @@ cp_finish_decl (tree decl, tree init, bo > > 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); > > } > > --- gcc/testsuite/c-c++-common/Winit-self3.c.jj 2023-01-12 15:49:56.759172518 +0100 > > +++ gcc/testsuite/c-c++-common/Winit-self3.c 2023-01-12 15:50:51.512384963 +0100 > > @@ -0,0 +1,36 @@ > > +/* PR c++/105593 */ > > +/* { dg-do compile } */ > > +/* { dg-options "-W -Wall" } */ > > + > > +void bar (int); > > + > > +static inline int > > +baz (void) > > +{ > > +#pragma GCC diagnostic push > > +#pragma GCC diagnostic ignored "-Winit-self" > > + int u = u; /* { dg-bogus "'u' is used uninitialized" } */ > > +#pragma GCC diagnostic pop > > + return u; > > +} > > + > > +void > > +foo (void) > > +{ > > + int u = baz (); > > + bar (u); > > +} > > + > > +static inline int > > +qux (void) > > +{ > > + int u = u; /* { dg-warning "'u' is used uninitialized" "" { target c++ } } */ > > + return u; /* { dg-message "'u' was declared here" "" { target c++ } .-1 } */ > > +} > > + > > +void > > +corge (void) > > +{ > > + int u = qux (); > > + bar (u); > > +} > > --- gcc/testsuite/c-c++-common/Winit-self4.c.jj 2023-01-12 15:50:15.233906776 +0100 > > +++ gcc/testsuite/c-c++-common/Winit-self4.c 2023-01-12 15:50:42.445515372 +0100 > > @@ -0,0 +1,36 @@ > > +/* PR c++/105593 */ > > +/* { dg-do compile } */ > > +/* { dg-options "-W -Wall -Winit-self" } */ > > + > > +void bar (int); > > + > > +static inline int > > +baz (void) > > +{ > > +#pragma GCC diagnostic push > > +#pragma GCC diagnostic ignored "-Winit-self" > > + int u = u; /* { dg-bogus "'u' is used uninitialized" } */ > > +#pragma GCC diagnostic pop > > + return u; > > +} > > + > > +void > > +foo (void) > > +{ > > + int u = baz (); > > + bar (u); > > +} > > + > > +static inline int > > +qux (void) > > +{ > > + int u = u; /* { dg-warning "'u' is used uninitialized" } */ > > + return u; /* { dg-message "'u' was declared here" "" { target *-*-* } .-1 } */ > > +} > > + > > +void > > +corge (void) > > +{ > > + int u = qux (); > > + bar (u); > > +} > > --- gcc/testsuite/c-c++-common/Winit-self5.c.jj 2023-01-12 15:51:01.045247847 +0100 > > +++ gcc/testsuite/c-c++-common/Winit-self5.c 2023-01-12 15:51:12.929076923 +0100 > > @@ -0,0 +1,36 @@ > > +/* PR c++/105593 */ > > +/* { dg-do compile } */ > > +/* { dg-options "-W -Wall -Wno-init-self" } */ > > + > > +void bar (int); > > + > > +static inline int > > +baz (void) > > +{ > > +#pragma GCC diagnostic push > > +#pragma GCC diagnostic ignored "-Winit-self" > > + int u = u; /* { dg-bogus "'u' is used uninitialized" } */ > > +#pragma GCC diagnostic pop > > + return u; > > +} > > + > > +void > > +foo (void) > > +{ > > + int u = baz (); > > + bar (u); > > +} > > + > > +static inline int > > +qux (void) > > +{ > > + int u = u; /* { dg-bogus "'u' is used uninitialized" } */ > > + return u; > > +} > > + > > +void > > +corge (void) > > +{ > > + int u = qux (); > > + bar (u); > > +} > > > > Jakub > > > Marek