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 [63.128.21.124]) by sourceware.org (Postfix) with ESMTP id A0653395383F for ; Tue, 27 Oct 2020 17:36:35 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org A0653395383F Received: from mail-qt1-f197.google.com (mail-qt1-f197.google.com [209.85.160.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-380-jdksLgtVM3yKBkh-7lVkoQ-1; Tue, 27 Oct 2020 13:36:33 -0400 X-MC-Unique: jdksLgtVM3yKBkh-7lVkoQ-1 Received: by mail-qt1-f197.google.com with SMTP id d1so1210585qtq.12 for ; Tue, 27 Oct 2020 10:36:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=NosBSB+OOP/4U7dJqV2Xq0daRE5jjhWli3QAhJXPZrQ=; b=HA+gytqcmeyjmn3idMqC3+izDY++AJbpiOEGA6KEs5kTqKH44+XLmDim1TJwOtaogA bXdZoJM4U6O+pxNv+2OvgHiBpea3T+cH5PYMNWz9ildT83eNR+hzhS2t992qXQY99Qqo mwz0socRNV+Ik0TX5MIz1TJx5y4kqKXdfxoEInOnScOM6QiZKunwZqIh9A3Wd9rpnVed cptlRAswqT2SgcGvm3tAkpqWiDvY7MDbcqlUOa75sYWq0u8hA34iRNWLHBFi2zLkf30S r4LI4s3IWNeutxcQAbe2uADL8+OrAa+OiICwxLVEO1XA+RqsQBz0se2ZS1hjfRPYj8al bt1w== X-Gm-Message-State: AOAM530otrD/FA+zqUR9Wscrtc9BfXgR4WiNHi5d7JS2QFtiJNL+SkLt sGytxoxjCbEk/UC5s9s1Ma3a7PwV51jmNDOpV4futIvkXvsVgYUBbglImzTfF/hYrmWKcf3TPB6 mf0SElGhBlYJ7f8ibDw== X-Received: by 2002:a05:620a:2144:: with SMTP id m4mr3224674qkm.269.1603820192406; Tue, 27 Oct 2020 10:36:32 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxviKHTEVLDXR+4Prq2isEQ8OpLJIYI9fO2juWfIabZH1Gsum+lU7Jkoeqjit6PM78vDwqraA== X-Received: by 2002:a05:620a:2144:: with SMTP id m4mr3224634qkm.269.1603820191967; Tue, 27 Oct 2020 10:36:31 -0700 (PDT) Received: from [192.168.1.148] (209-6-216-142.s141.c3-0.smr-cbr1.sbo-smr.ma.cable.rcncustomer.com. [209.6.216.142]) by smtp.gmail.com with ESMTPSA id d188sm1176310qkb.10.2020.10.27.10.36.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 27 Oct 2020 10:36:31 -0700 (PDT) Subject: Re: [PATCH] c++: Prevent warnings for value-dependent exprs [PR96742] To: Marek Polacek , GCC Patches References: <20201024225231.2369564-1-polacek@redhat.com> From: Jason Merrill Message-ID: Date: Tue, 27 Oct 2020 13:36:30 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20201024225231.2369564-1-polacek@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-17.6 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_NONE, RCVD_IN_MSPIKE_H5, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) 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: Tue, 27 Oct 2020 17:36:37 -0000 On 10/24/20 6:52 PM, Marek Polacek wrote: > Here, in r11-155, I changed the call to uses_template_parms to > type_dependent_expression_p_push to avoid a crash in C++98 in > value_dependent_expression_p on a non-constant expression. But that > prompted a host of complaints that we now warn for value-dependent > expressions in templates. Those warnings are technically valid, but > people still don't want them because they're awkward to avoid. So let's > partially revert my earlier fix and make sure that we don't ICE in > value_dependent_expression_p by checking potential_constant_expression > first. > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/10? > > gcc/cp/ChangeLog: > > PR c++/96675 > PR c++/96742 > * pt.c (tsubst_copy_and_build): Call uses_template_parms instead of > type_dependent_expression_p_push. Only call uses_template_parms > for expressions that are potential_constant_expression. > > gcc/testsuite/ChangeLog: > > PR c++/96675 > PR c++/96742 > * g++.dg/warn/Wdiv-by-zero-3.C: Turn dg-warning into dg-bogus. > * g++.dg/warn/Wtautological-compare3.C: New test. > * g++.dg/warn/Wtype-limits5.C: New test. > * g++.old-deja/g++.pt/crash10.C: Remove dg-warning. > --- > gcc/cp/pt.c | 6 ++++-- > gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C | 6 ++++-- > gcc/testsuite/g++.dg/warn/Wtautological-compare3.C | 11 +++++++++++ > gcc/testsuite/g++.dg/warn/Wtype-limits5.C | 11 +++++++++++ > gcc/testsuite/g++.old-deja/g++.pt/crash10.C | 1 - > 5 files changed, 30 insertions(+), 5 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/warn/Wtautological-compare3.C > create mode 100644 gcc/testsuite/g++.dg/warn/Wtype-limits5.C > > diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c > index dc664ec3798..8aa0bc2c0d8 100644 > --- a/gcc/cp/pt.c > +++ b/gcc/cp/pt.c > @@ -19618,8 +19618,10 @@ tsubst_copy_and_build (tree t, > { > /* If T was type-dependent, suppress warnings that depend on the range > of the types involved. */ > - bool was_dep = type_dependent_expression_p_push (t); > - > + ++processing_template_decl; > + const bool was_dep = (!potential_constant_expression (t) > + || uses_template_parms (t)); We don't want to suppress warnings for a non-constant expression that uses no template parms. So maybe potential_c_e ? value_d : type_d ? Or perhaps instantiation_dependent_expression_p. > + --processing_template_decl; > tree op0 = RECUR (TREE_OPERAND (t, 0)); > tree op1 = RECUR (TREE_OPERAND (t, 1)); > > diff --git a/gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C b/gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C > index 424eb0c3d49..01f691f2878 100644 > --- a/gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C > +++ b/gcc/testsuite/g++.dg/warn/Wdiv-by-zero-3.C > @@ -5,8 +5,10 @@ foo (T t, int i) > { > int m1 = 10 / t; > int m2 = 10 / i; > - int m3 = 10 / (sizeof(T) - sizeof(int)); // { dg-warning "division by" } > - int m4 = 10 / N; // { dg-warning "division by" } > + // People don't want to see warnings for type- or value-dependent > + // expressions. > + int m3 = 10 / (sizeof(T) - sizeof(int)); // { dg-bogus "division by" } > + int m4 = 10 / N; // { dg-bogus "division by" } > return m1 + m2 + m3 + m4; > } > > diff --git a/gcc/testsuite/g++.dg/warn/Wtautological-compare3.C b/gcc/testsuite/g++.dg/warn/Wtautological-compare3.C > new file mode 100644 > index 00000000000..89bf1b619a6 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/warn/Wtautological-compare3.C > @@ -0,0 +1,11 @@ > +// PR c++/96675 > +// { dg-do compile { target c++11 } } > +// { dg-additional-options "-Wtautological-compare" } > + > +template > +constexpr bool f(char d) { > + return 'a' <= c && c <= 'z' ? (d | 0x20) == c : > + 'A' <= c && c <= 'Z' ? (d & ~0x20) == c : > + d == c; > +} > +static_assert(f<'p'>('P'), ""); > diff --git a/gcc/testsuite/g++.dg/warn/Wtype-limits5.C b/gcc/testsuite/g++.dg/warn/Wtype-limits5.C > new file mode 100644 > index 00000000000..5e79123b622 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/warn/Wtype-limits5.C > @@ -0,0 +1,11 @@ > +// PR c++/96742 > +// { dg-additional-options "-Wtype-limits" } > + > +template > +bool f(unsigned x) { > + return unsigned(x < N); > +} > + > +int main() { > + f<0>(1); > +} > diff --git a/gcc/testsuite/g++.old-deja/g++.pt/crash10.C b/gcc/testsuite/g++.old-deja/g++.pt/crash10.C > index 012e3d0c11b..a84b19004ee 100644 > --- a/gcc/testsuite/g++.old-deja/g++.pt/crash10.C > +++ b/gcc/testsuite/g++.old-deja/g++.pt/crash10.C > @@ -6,7 +6,6 @@ public: > enum { val = (N == 0) ? M : GCD::val }; > // { dg-error "constant expression" "valid" { target *-*-* } .-1 } > // { dg-message "template argument" "valid" { target *-*-* } .-2 } > -// { dg-warning "division by" "" { target *-*-* } .-3 } > }; > > int main() { > > base-commit: 1aeb7d7d67d167297ca2f4a97ef20f68e7546b4c >