From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by sourceware.org (Postfix) with ESMTPS id 36CD53857413 for ; Wed, 27 Jul 2022 06:41:13 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 36CD53857413 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 3B80437B28; Wed, 27 Jul 2022 06:41:10 +0000 (UTC) Received: from wotan.suse.de (wotan.suse.de [10.160.0.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 151712C141; Wed, 27 Jul 2022 06:41:10 +0000 (UTC) Date: Wed, 27 Jul 2022 06:41:09 +0000 (UTC) From: Richard Biener To: Marek Polacek cc: GCC Patches , Jason Merrill , Joseph Myers Subject: Re: [PATCH] c-family: Honor -Wno-init-self for cv-qual vars [PR102633] In-Reply-To: <20220726190340.432777-1-polacek@redhat.com> Message-ID: References: <20220726190340.432777-1-polacek@redhat.com> User-Agent: Alpine 2.22 (LSU 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Spam-Status: No, score=-11.0 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, SPF_HELO_NONE, SPF_PASS, 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 X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 27 Jul 2022 06:41:15 -0000 On Tue, 26 Jul 2022, Marek Polacek wrote: > Since r11-5188-g32934a4f45a721, we drop qualifiers during l-to-r > conversion by creating a NOP_EXPR. For e.g. > > const int i = i; > > that means that the DECL_INITIAL is '(int) i' and not 'i' anymore. > Consequently, we don't suppress_warning here: > > 711 case DECL_EXPR: > 715 if (VAR_P (DECL_EXPR_DECL (*expr_p)) > 716 && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p)) > 717 && !TREE_STATIC (DECL_EXPR_DECL (*expr_p)) > 718 && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == DECL_EXPR_DECL (*expr_p)) > 719 && !warn_init_self) > 720 suppress_warning (DECL_EXPR_DECL (*expr_p), OPT_Winit_self); > > because of the check on line 718 -- (int) i is not i. So -Wno-init-self > doesn't disable the warning as it's supposed to. > > The following patch fixes it...except it doesn't, for volatile variables > in C++. The problem is that for > > volatile int k = k; > > we see that the initializer has TREE_SIDE_EFFECTS, so we perform dynamic > initialization. So there's no DECL_INITIAL and the suppress_warning > call above is never done. I suppose we could amend get_no_uninit_warning > to return true for volatile-qualified expressions. I mean, can we ever > say for a fact that a volatile variable is uninitialized? As I said in the bug the bug is probably that we emit uninitialized diagnostics for volatiles at all? OTOH 'volatile' is recommended for vars live around setjmp/longjmp and there diagnostics would be welcome. It's probably the difference between "compiler-hands-off" and "hardware-controlled" :/ > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > PR middle-end/102633 > > gcc/c-family/ChangeLog: > > * c-gimplify.cc (c_gimplify_expr): Strip NOPs of DECL_INITIAL. > > gcc/testsuite/ChangeLog: > > * c-c++-common/Winit-self1.c: New test. > * c-c++-common/Winit-self2.c: New test. > --- > gcc/c-family/c-gimplify.cc | 18 +++++++------ > gcc/testsuite/c-c++-common/Winit-self1.c | 32 ++++++++++++++++++++++++ > gcc/testsuite/c-c++-common/Winit-self2.c | 31 +++++++++++++++++++++++ > 3 files changed, 74 insertions(+), 7 deletions(-) > create mode 100644 gcc/testsuite/c-c++-common/Winit-self1.c > create mode 100644 gcc/testsuite/c-c++-common/Winit-self2.c > > diff --git a/gcc/c-family/c-gimplify.cc b/gcc/c-family/c-gimplify.cc > index a6f26c9b0d3..2e011830846 100644 > --- a/gcc/c-family/c-gimplify.cc > +++ b/gcc/c-family/c-gimplify.cc > @@ -712,13 +712,17 @@ c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED, > /* This is handled mostly by gimplify.cc, but we have to deal with > not warning about int x = x; as it is a GCC extension to turn off > this warning but only if warn_init_self is zero. */ > - if (VAR_P (DECL_EXPR_DECL (*expr_p)) > - && !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p)) > - && !TREE_STATIC (DECL_EXPR_DECL (*expr_p)) > - && (DECL_INITIAL (DECL_EXPR_DECL (*expr_p)) == DECL_EXPR_DECL (*expr_p)) > - && !warn_init_self) > - suppress_warning (DECL_EXPR_DECL (*expr_p), OPT_Winit_self); > - break; > + { > + tree &decl = DECL_EXPR_DECL (*expr_p); > + if (VAR_P (decl) > + && !DECL_EXTERNAL (decl) > + && !TREE_STATIC (decl) > + && (DECL_INITIAL (decl) > + && tree_strip_nop_conversions (DECL_INITIAL (decl)) == decl) > + && !warn_init_self) > + suppress_warning (decl, OPT_Winit_self); > + break; > + } > > case PREINCREMENT_EXPR: > case PREDECREMENT_EXPR: > diff --git a/gcc/testsuite/c-c++-common/Winit-self1.c b/gcc/testsuite/c-c++-common/Winit-self1.c > new file mode 100644 > index 00000000000..2a1a755fc71 > --- /dev/null > +++ b/gcc/testsuite/c-c++-common/Winit-self1.c > @@ -0,0 +1,32 @@ > +/* PR middle-end/102633 */ > +/* { dg-do compile } */ > +/* { dg-options "-Wuninitialized -Wno-init-self" } */ > + > +int > +fn1 (void) > +{ > + int i = i; > + return i; > +} > + > +int > +fn2 () > +{ > + const int j = j; > + return j; > +} > + > +int > +fn3 () > +{ > + /* ??? Do we want this warning in C++? Probably not with -Wno-init-self. */ > + volatile int k = k; /* { dg-warning "used uninitialized" "" { target c++ } } */ > + return k; > +} > + > +int > +fn4 () > +{ > + const volatile int l = l; /* { dg-warning "used uninitialized" "" { target c++ } } */ > + return l; > +} > diff --git a/gcc/testsuite/c-c++-common/Winit-self2.c b/gcc/testsuite/c-c++-common/Winit-self2.c > new file mode 100644 > index 00000000000..13aa9efdf26 > --- /dev/null > +++ b/gcc/testsuite/c-c++-common/Winit-self2.c > @@ -0,0 +1,31 @@ > +/* PR middle-end/102633 */ > +/* { dg-do compile } */ > +/* { dg-options "-Wuninitialized -Winit-self" } */ > + > +int > +fn1 (void) > +{ > + int i = i; /* { dg-warning "used uninitialized" } */ > + return i; > +} > + > +int > +fn2 () > +{ > + const int j = j; /* { dg-warning "used uninitialized" } */ > + return j; > +} > + > +int > +fn3 () > +{ > + volatile int k = k; /* { dg-warning "used uninitialized" } */ > + return k; > +} > + > +int > +fn4 () > +{ > + const volatile int l = l; /* { dg-warning "used uninitialized" } */ > + return l; > +} > > base-commit: 600956c81c784f4a0cc9d10f6e03e01847afd961 > -- Richard Biener SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman; HRB 36809 (AG Nuernberg)