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 [216.205.24.124]) by sourceware.org (Postfix) with ESMTP id 7FB713858C2C for ; Thu, 30 Sep 2021 21:56:53 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 7FB713858C2C Received: from mail-qt1-f198.google.com (mail-qt1-f198.google.com [209.85.160.198]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-571-X_rgqyY5Nmu-WCWm9pZ5QQ-1; Thu, 30 Sep 2021 17:56:51 -0400 X-MC-Unique: X_rgqyY5Nmu-WCWm9pZ5QQ-1 Received: by mail-qt1-f198.google.com with SMTP id k1-20020ac80201000000b002a7200b449eso1456131qtg.18 for ; Thu, 30 Sep 2021 14:56:51 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=wbSjzN65sKsKGXhmf3sOiS3yXVdkry7qIvyEeVYe5U8=; b=cQTOKE3uyJvy62DNoXSlj/QV1dWBMWSz5Jh7DCgh97JOrld9zZvUKkFCKCRFaR+glt Sz2RXflXuj9lvdRI64PH+0lt0u12VlO/ZL6oocss8CgRY+bCW3949CG6YqiZSd9MdeqX 2fKKs1i3zjR8zpn/yclnXGcEdKR9++nozvHRvycXGMj2x3+N7zFp8SXfdEkUDeBQE42r IukNvHYfKxAu4+CxhvUEDeiYS8oylekPpoZ7LXz/x6Hu+kKrz5KGn9ej1xIi6Egs2qDZ BqantOrkWM/rJGx02TGkvsOuHD9PszOuaRu0fk8iPbSd2qbjYOb89CHNtbFmYWeO9dxI iYTA== X-Gm-Message-State: AOAM532XCFSBs6dpkoXBr7buMT2TzdbUonCWrdUgxaomiTthDB0SPlHo dfk+pvRq9DWzwyqe/LnmeXMVoTK9cLxlZltAM/ezaTyGKGOMUvPAik4fJwgStXVoAEU3s8fuBrR RCjgFEW22msS4JnbhKw== X-Received: by 2002:ac8:6113:: with SMTP id a19mr1744197qtm.307.1633039011292; Thu, 30 Sep 2021 14:56:51 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwRoKvKfLi8y7Yg1mVjMqgks1fUwSoy2GjlqLkgG10sgeUQVnsY8rzb/qOwi0NN9wqP02ieRg== X-Received: by 2002:ac8:6113:: with SMTP id a19mr1744125qtm.307.1633039010128; Thu, 30 Sep 2021 14:56:50 -0700 (PDT) Received: from redhat.com ([2601:184:4780:4310::9b82]) by smtp.gmail.com with ESMTPSA id u21sm2021008qkk.82.2021.09.30.14.56.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Sep 2021 14:56:49 -0700 (PDT) Date: Thu, 30 Sep 2021 17:56:48 -0400 From: Marek Polacek To: Jason Merrill Cc: GCC Patches Subject: Re: [PATCH] c++: Implement C++20 -Wdeprecated-array-compare [PR97573] Message-ID: References: <20210930145031.23104-1-polacek@redhat.com> <7962e5b5-9e10-60f8-9a4e-26e86040a542@redhat.com> MIME-Version: 1.0 In-Reply-To: <7962e5b5-9e10-60f8-9a4e-26e86040a542@redhat.com> User-Agent: Mutt/2.0.7 (2021-05-04) 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=-13.2 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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, 30 Sep 2021 21:56:55 -0000 On Thu, Sep 30, 2021 at 03:34:24PM -0400, Jason Merrill wrote: > On 9/30/21 10:50, Marek Polacek wrote: > > This patch addresses one of my leftovers from GCC 11. C++20 introduced > > [depr.array.comp]: > > "Equality and relational comparisons between two operands of array type are > > deprecated." > > so this patch adds -Wdeprecated-array-compare (enabled by default in C++20). > > Why not enable it by default in all modes? It was always pretty dubious > code. Sure, it could be done, but it kind of complicates things: we'd probably need a different option and a different message because it seems incorrect to say "deprecated" in e.g. C++17 when this was only deprecated in C++20. I'd rather not add another option; if it stays -Wdeprecated-array-compare but -Wno-deprecated doesn't turn it off that also seems weird. I could rename it to -Warray-compare, enable by -Wall, and only append "is deprecated" to the warning message in C++20. Does that seem better? > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > > > PR c++/97573 > > > > gcc/c-family/ChangeLog: > > > > * c-opts.c (c_common_post_options): In C++20, turn on > > -Wdeprecated-array-compare. > > * c.opt (Wdeprecated-array-compare): New option. > > > > gcc/cp/ChangeLog: > > > > * typeck.c (do_warn_deprecated_array_compare): New. > > (cp_build_binary_op): Call it for equality and relational comparisons. > > > > gcc/ChangeLog: > > > > * doc/invoke.texi: Document -Wdeprecated-array-compare. > > > > gcc/testsuite/ChangeLog: > > > > * g++.dg/tree-ssa/pr15791-1.C: Add dg-warning. > > * g++.dg/cpp2a/array-comp1.C: New test. > > * g++.dg/cpp2a/array-comp2.C: New test. > > * g++.dg/cpp2a/array-comp3.C: New test. > > --- > > gcc/c-family/c-opts.c | 5 ++++ > > gcc/c-family/c.opt | 4 +++ > > gcc/cp/typeck.c | 28 +++++++++++++++++++ > > gcc/doc/invoke.texi | 19 ++++++++++++- > > gcc/testsuite/g++.dg/cpp2a/array-comp1.C | 34 +++++++++++++++++++++++ > > gcc/testsuite/g++.dg/cpp2a/array-comp2.C | 31 +++++++++++++++++++++ > > gcc/testsuite/g++.dg/cpp2a/array-comp3.C | 29 +++++++++++++++++++ > > gcc/testsuite/g++.dg/tree-ssa/pr15791-1.C | 2 +- > > 8 files changed, 150 insertions(+), 2 deletions(-) > > create mode 100644 gcc/testsuite/g++.dg/cpp2a/array-comp1.C > > create mode 100644 gcc/testsuite/g++.dg/cpp2a/array-comp2.C > > create mode 100644 gcc/testsuite/g++.dg/cpp2a/array-comp3.C > > > > diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c > > index 3eaab5e1530..00b52cc5e12 100644 > > --- a/gcc/c-family/c-opts.c > > +++ b/gcc/c-family/c-opts.c > > @@ -962,6 +962,11 @@ c_common_post_options (const char **pfilename) > > warn_deprecated_enum_float_conv, > > cxx_dialect >= cxx20 && warn_deprecated); > > + /* -Wdeprecated-array-compare is enabled by default in C++20. */ > > + SET_OPTION_IF_UNSET (&global_options, &global_options_set, > > + warn_deprecated_array_compare, > > + cxx_dialect >= cxx20 && warn_deprecated); > > + > > /* Declone C++ 'structors if -Os. */ > > if (flag_declone_ctor_dtor == -1) > > flag_declone_ctor_dtor = optimize_size; > > diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt > > index 9c151d19870..a4f0ea68594 100644 > > --- a/gcc/c-family/c.opt > > +++ b/gcc/c-family/c.opt > > @@ -540,6 +540,10 @@ Wdeprecated > > C C++ ObjC ObjC++ CPP(cpp_warn_deprecated) CppReason(CPP_W_DEPRECATED) > > ; Documented in common.opt > > +Wdeprecated-array-compare > > +C++ ObjC++ Var(warn_deprecated_array_compare) Warning > > +Warn about deprecated comparisons between two operands of array type. > > + > > Wdeprecated-copy > > C++ ObjC++ Var(warn_deprecated_copy) Warning LangEnabledBy(C++ ObjC++, Wextra) > > Mark implicitly-declared copy operations as deprecated if the class has a > > diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c > > index a2398dbe660..1e3a41104d6 100644 > > --- a/gcc/cp/typeck.c > > +++ b/gcc/cp/typeck.c > > @@ -40,6 +40,7 @@ along with GCC; see the file COPYING3. If not see > > #include "attribs.h" > > #include "asan.h" > > #include "gimplify.h" > > +#include "tree-pretty-print.h" > > static tree cp_build_addr_expr_strict (tree, tsubst_flags_t); > > static tree cp_build_function_call (tree, tree, tsubst_flags_t); > > @@ -4725,6 +4726,21 @@ do_warn_enum_conversions (location_t loc, enum tree_code code, tree type0, > > } > > } > > +/* Warn about C++20 [depr.array.comp] array comparisons: "Equality > > + and relational comparisons between two operands of array type are > > + deprecated." */ > > + > > +static inline void > > +do_warn_deprecated_array_compare (location_t location, tree_code code, > > + tree op0, tree op1) > > +{ > > + if (warning_at (location, OPT_Wdeprecated_array_compare, > > + "comparison between two arrays is deprecated")) > > + inform (location, "use unary %<+%> which decays operands to pointers " > > + "or %<&%D[0] %s &%D[0]%> to compare the addresses", > > + op0, op_symbol_code (code), op1); > > +} > > + > > /* Build a binary-operation expression without default conversions. > > CODE is the kind of expression to build. > > LOCATION is the location_t of the operator in the source code. > > @@ -5289,6 +5305,11 @@ cp_build_binary_op (const op_location_t &location, > > warning_at (location, OPT_Waddress, > > "comparison with string literal results in " > > "unspecified behavior"); > > + else if (TREE_CODE (TREE_TYPE (orig_op0)) == ARRAY_TYPE > > + && TREE_CODE (TREE_TYPE (orig_op1)) == ARRAY_TYPE) > > + do_warn_deprecated_array_compare (location, code, > > + stripped_orig_op0, > > + stripped_orig_op1); > > } > > build_type = boolean_type_node; > > @@ -5559,6 +5580,13 @@ cp_build_binary_op (const op_location_t &location, > > "comparison with string literal results " > > "in unspecified behavior"); > > } > > + else if (TREE_CODE (TREE_TYPE (orig_op0)) == ARRAY_TYPE > > + && TREE_CODE (TREE_TYPE (orig_op1)) == ARRAY_TYPE > > + && code != SPACESHIP_EXPR > > What happens if you try to compare them with <=>? That's always an error so printing a warning is redundant. Marek