From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id A26323858283 for ; Thu, 11 Aug 2022 22:31:06 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org A26323858283 Received: from mail-oi1-f200.google.com (mail-oi1-f200.google.com [209.85.167.200]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-39-uApAUKIhMu-k-GqBXacuEg-1; Thu, 11 Aug 2022 18:31:05 -0400 X-MC-Unique: uApAUKIhMu-k-GqBXacuEg-1 Received: by mail-oi1-f200.google.com with SMTP id l22-20020a544516000000b0033a87b30320so7905346oil.3 for ; Thu, 11 Aug 2022 15:31:05 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc; bh=DTPWVX/CySqyIExYaKgfX7Sh37KbUGpNHI2l31DLspU=; b=A4tVzEfujE61lgskiRjdmea4cKdCE2shUbit38S2GYgiACcCiJMvGrqIbyoqhwRGt+ IhSJaadZhMq1fcjwZ8xyTTeqeE4WTkXKIxlUBrMSfPxushnwIqVMHvkDSuL+j8rMADIw 42Mz4HHMja4gPrvOatjmbB2xmKx7zrvvNRwM7M0LqNaLxYWRJxnhGSI5JbuXzjKvIroZ 6Li63FsUN6D8I99vtbN1K/h1IAZIwxXY7cjf8IQCkdahswUuZBvAwdxauGPBwnYqKzYX 3rLMoVlVjgBCYYZx2N7+idEW8ZoJw9wiRU9DVs69Xrjl/8bt40euiXk3OiNhh4UhkrvR nK5A== X-Gm-Message-State: ACgBeo3xwf70x9FLr0SaGxXjTMKM/25/RpzUXdi+8NKiXUVWJ/LiM2ea Zb+jTKrjmiTM2LvP1AFLtnlZ2vmLgf9gEIDvbdUd14JeOX8kuAFri/umV2WEE2mb88mEweQoMMA o0C3MV6Rxaxc5hDEuHA== X-Received: by 2002:a05:6870:f69b:b0:10d:a0d3:4175 with SMTP id el27-20020a056870f69b00b0010da0d34175mr4397499oab.53.1660257064486; Thu, 11 Aug 2022 15:31:04 -0700 (PDT) X-Google-Smtp-Source: AA6agR57AceIs2ArsoSfyUlxYDpElhLIx3c6rd+hCSB6LIELcn8IM0xf5n1zXO3vZNtngaB2JmCFRQ== X-Received: by 2002:a05:6870:f69b:b0:10d:a0d3:4175 with SMTP id el27-20020a056870f69b00b0010da0d34175mr4397481oab.53.1660257064124; Thu, 11 Aug 2022 15:31:04 -0700 (PDT) Received: from [192.168.33.40] ([72.2.237.35]) by smtp.gmail.com with ESMTPSA id eh5-20020a056870f58500b0010e63d0afbbsm67907oab.55.2022.08.11.15.30.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Aug 2022 15:31:03 -0700 (PDT) Message-ID: <5e1e216c-d354-db59-fa72-c52ca79deae5@redhat.com> Date: Thu, 11 Aug 2022 14:30:23 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH v2] c-family: Honor -Wno-init-self for cv-qual vars [PR102633] To: Marek Polacek Cc: GCC Patches , Joseph Myers , Richard Biener References: <20220726190340.432777-1-polacek@redhat.com> <51485fa8-a1c0-c019-c2bb-f4599fe34ca4@redhat.com> <01d3db21-2cf9-fa81-e1d1-973c479e22a3@redhat.com> From: Jason Merrill In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-13.4 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, NICE_REPLY_A, RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE 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: Thu, 11 Aug 2022 22:31:08 -0000 On 8/8/22 12:06, Marek Polacek wrote: > On Sat, Aug 06, 2022 at 03:29:05PM -0700, Jason Merrill wrote: >> On 7/26/22 14:31, Marek Polacek wrote: >>> On Tue, Jul 26, 2022 at 04:24:18PM -0400, Jason Merrill wrote: >>>> On 7/26/22 15:03, 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? >>>>> >>>>> 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. >>>> >>>> I wonder if we want to handle this i = i case earlier, like in finish_decl. >>> >>> I could, something like >>> >>> @@ -5381,7 +5381,14 @@ finish_decl (tree decl, location_t init_loc, tree init, >>> init = NULL_TREE; >>> >>> if (init) >>> - store_init_value (init_loc, decl, init, origtype); >>> + { >>> + /* In the self-init case, undo the artificial NOP_EXPR we may have >>> + added in convert_lvalue_to_rvalue so that c_gimplify_expr/DECL_EXPR >>> + can perform suppress_warning. */ >>> + if (TREE_CODE (init) == NOP_EXPR && TREE_OPERAND (init, 0) == decl) >>> + init = TREE_OPERAND (init, 0); >>> + store_init_value (init_loc, decl, init, origtype); >>> + } >>> >>> but then I'd have to do the same thing in cp_finish_decl because >>> decay_conversion also adds a NOP_EXPR for cv-qualified non-class prvalues. >>> Is that what we want? To me that seems less clean than having c_gimplify_expr >>> see through NOP_EXPRs. >> >> I was thinking of checking the form of the initializer before >> decay_conversion or anything else messes with it, and calling >> suppress_warning at that point instead of in c_gimplify_expr. > > Aaah, okay. Here's a patch that does it. In the C FE it has to > happen really early. Now both front ends behave the same wrt volatiles! > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? LGTM. > -- >8 -- > 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 by moving the suppress_warning call from > c_gimplify_expr to the front ends, at points where we haven't created > the NOP_EXPR yet. > > PR middle-end/102633 > > gcc/c-family/ChangeLog: > > * c-gimplify.cc (c_gimplify_expr) : Don't call > suppress_warning here. > > gcc/c/ChangeLog: > > * c-parser.cc (c_parser_initializer): Add new tree parameter. Use it. > Call suppress_warning. > (c_parser_declaration_or_fndef): Pass d down to c_parser_initializer. > (c_parser_omp_declare_reduction): Pass omp_priv down to > c_parser_initializer. > > gcc/cp/ChangeLog: > > * decl.cc (cp_finish_decl): Call suppress_warning. > > 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 | 12 --------- > gcc/c/c-parser.cc | 19 ++++++++++++--- > gcc/cp/decl.cc | 8 ++++++ > gcc/testsuite/c-c++-common/Winit-self1.c | 31 ++++++++++++++++++++++++ > gcc/testsuite/c-c++-common/Winit-self2.c | 31 ++++++++++++++++++++++++ > 5 files changed, 85 insertions(+), 16 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..039a4b93230 100644 > --- a/gcc/c-family/c-gimplify.cc > +++ b/gcc/c-family/c-gimplify.cc > @@ -708,18 +708,6 @@ c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED, > break; > } > > - case DECL_EXPR: > - /* 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; > - > case PREINCREMENT_EXPR: > case PREDECREMENT_EXPR: > case POSTINCREMENT_EXPR: > diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc > index 92049d1a101..6ed17ed9c48 100644 > --- a/gcc/c/c-parser.cc > +++ b/gcc/c/c-parser.cc > @@ -1521,7 +1521,7 @@ static struct c_arg_info *c_parser_parms_list_declarator (c_parser *, tree, > static struct c_parm *c_parser_parameter_declaration (c_parser *, tree, bool); > static tree c_parser_simple_asm_expr (c_parser *); > static tree c_parser_gnu_attributes (c_parser *); > -static struct c_expr c_parser_initializer (c_parser *); > +static struct c_expr c_parser_initializer (c_parser *, tree); > static struct c_expr c_parser_braced_init (c_parser *, tree, bool, > struct obstack *); > static void c_parser_initelt (c_parser *, struct obstack *); > @@ -2286,7 +2286,7 @@ c_parser_declaration_or_fndef (c_parser *parser, bool fndef_ok, > int flag_sanitize_save = flag_sanitize; > if (TREE_CODE (d) == PARM_DECL) > flag_sanitize = 0; > - init = c_parser_initializer (parser); > + init = c_parser_initializer (parser, d); > flag_sanitize = flag_sanitize_save; > finish_init (); > } > @@ -5211,11 +5211,13 @@ c_parser_type_name (c_parser *parser, bool alignas_ok) > Any expression without commas is accepted in the syntax for the > constant-expressions, with non-constant expressions rejected later. > > + DECL is the declaration we're parsing this initializer for. > + > This function is only used for top-level initializers; for nested > ones, see c_parser_initval. */ > > static struct c_expr > -c_parser_initializer (c_parser *parser) > +c_parser_initializer (c_parser *parser, tree decl) > { > if (c_parser_next_token_is (parser, CPP_OPEN_BRACE)) > return c_parser_braced_init (parser, NULL_TREE, false, NULL); > @@ -5224,6 +5226,15 @@ c_parser_initializer (c_parser *parser) > struct c_expr ret; > location_t loc = c_parser_peek_token (parser)->location; > ret = c_parser_expr_no_commas (parser, NULL); > + /* 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) > + && !DECL_EXTERNAL (decl) > + && !TREE_STATIC (decl) > + && ret.value == decl > + && !warn_init_self) > + suppress_warning (decl, OPT_Winit_self); > if (TREE_CODE (ret.value) != STRING_CST > && TREE_CODE (ret.value) != COMPOUND_LITERAL_EXPR) > ret = convert_lvalue_to_rvalue (loc, ret, true, true); > @@ -22576,7 +22587,7 @@ c_parser_omp_declare_reduction (c_parser *parser, enum pragma_context context) > location_t loc = c_parser_peek_token (parser)->location; > rich_location richloc (line_table, loc); > start_init (omp_priv, NULL_TREE, 0, &richloc); > - struct c_expr init = c_parser_initializer (parser); > + struct c_expr init = c_parser_initializer (parser, omp_priv); > finish_init (); > finish_decl (omp_priv, loc, init.value, > init.original_type, NULL_TREE); > diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc > index 70ad681467e..ff56fddba54 100644 > --- a/gcc/cp/decl.cc > +++ b/gcc/cp/decl.cc > @@ -8253,6 +8253,14 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p, > && !TYPE_REF_P (type)) > TREE_CONSTANT (decl) = 1; > } > + /* 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 (!DECL_EXTERNAL (decl) > + && !TREE_STATIC (decl) > + && decl == tree_strip_any_location_wrapper (init) > + && !warn_init_self) > + suppress_warning (decl, OPT_Winit_self); > } > > if (flag_openmp > 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..740b83b5e9f > --- /dev/null > +++ b/gcc/testsuite/c-c++-common/Winit-self1.c > @@ -0,0 +1,31 @@ > +/* 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 () > +{ > + volatile int k = k; > + return k; > +} > + > +int > +fn4 () > +{ > + const volatile int l = l; > + 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: 21c7aab09805d0c8c7695c8a69c8715d673a739a