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 E3C213858D28 for ; Tue, 18 Jan 2022 16:05:42 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org E3C213858D28 Received: from mail-qt1-f199.google.com (mail-qt1-f199.google.com [209.85.160.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-5-CCWj97PtPHu_thNcfqpZAw-1; Tue, 18 Jan 2022 11:05:41 -0500 X-MC-Unique: CCWj97PtPHu_thNcfqpZAw-1 Received: by mail-qt1-f199.google.com with SMTP id c10-20020ac84e0a000000b002c9c1be5a00so7589085qtw.3 for ; Tue, 18 Jan 2022 08:05:39 -0800 (PST) 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=5tNgDAnbRUn0tfQJ8ka23+uUkB2SNKtBefskPc5LLvU=; b=H9iOpdsieI/qhylvNV6mWjxNqp8TXqS5RL4wxKkEoGjPwKJeHYkMihr5qdW2HZ5UM8 gOM8rHSv9DG585cqJSLAPj9DQpd12J1EgS9GEYYgG3Dj6LW1QlF6doA3XQZtnN2HdTyd jlGtVkO5pkZgV8JiSXylopvtYxl29JWbrI9GeJ9g95cb21awzBikJZ/pC7z4BN5F+TXM IfGQqQJ9PltN9r/myDKWu1v+XcRjQvjfO9lBDySHFk35+gd9p/K/phEenlSZJM9AWh0F HkWVExb8GMIeP+gxxsg4nzqYzSRSqy+CKaftsDg1w7JpasoPm7uskySxP5B7lzlDRFPd Sktw== X-Gm-Message-State: AOAM530RW/6D46a7kqLu/YFtCKcUStdz2lfYOznKrHz+B9rNYknzPz0J 1wuSHO28vazwext5LxPW3SCZI1mpfqr6rmc5KODyuscDsigzwYtrYbKFf/DBZtvlCTaBoCz7Cy2 Sk2XUqUiFdfdtRvA7Yg== X-Received: by 2002:a05:620a:1a18:: with SMTP id bk24mr6929716qkb.2.1642521935838; Tue, 18 Jan 2022 08:05:35 -0800 (PST) X-Google-Smtp-Source: ABdhPJxQVK/KlFExnp2nUwoGD2z9HIktQV8HisQEsl4g+tyBppAUK+YjHyyz6FeYTaBfMrPCq2fcLw== X-Received: by 2002:a05:620a:1a18:: with SMTP id bk24mr6929681qkb.2.1642521935523; Tue, 18 Jan 2022 08:05:35 -0800 (PST) Received: from redhat.com ([2601:184:4780:4310::7156]) by smtp.gmail.com with ESMTPSA id d1sm3654311qty.79.2022.01.18.08.05.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Jan 2022 08:05:34 -0800 (PST) Date: Tue, 18 Jan 2022 11:05:33 -0500 From: Marek Polacek To: Jason Merrill Cc: Nathan Sidwell , GCC Patches Subject: Re: [PATCH] c++: ICE with noexcept and canonical types [PR101715] Message-ID: References: <20220115002249.366484-1-polacek@redhat.com> <1ef32dc7-8b16-9fa4-7c7c-649632be6768@redhat.com> MIME-Version: 1.0 In-Reply-To: <1ef32dc7-8b16-9fa4-7c7c-649632be6768@redhat.com> User-Agent: Mutt/2.1.5 (2021-12-30) 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=-12.8 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_H3, RCVD_IN_MSPIKE_WL, 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: Tue, 18 Jan 2022 16:05:44 -0000 On Mon, Jan 17, 2022 at 01:48:48PM -0500, Jason Merrill wrote: > On 1/14/22 19:22, Marek Polacek wrote: > > This is a "canonical types differ for identical types" ICE, which started > > with r11-4682. It's a bit tricky to explain. Consider: > > > > template struct S { > > S bar() noexcept(T::value); // #1 > > S foo() noexcept(T::value); // #2 > > }; > > > > template S S::foo() noexcept(T::value) {} // #3 > > > > We ICE because #3 and #2 have the same type, but their canonical types > > differ: TYPE_CANONICAL (#3) == #2 but TYPE_CANONICAL (#2) == #1. > > > > The member functions #1 and #2 have the same type. However, since their > > noexcept-specifier is deferred, when parsing them, we create a variant for > > both of them, because DEFERRED_PARSE cannot be compared. In other words, > > build_cp_fntype_variant's > > > > tree v = TYPE_MAIN_VARIANT (type); > > for (; v; v = TYPE_NEXT_VARIANT (v)) > > if (cp_check_qualified_type (v, type, type_quals, rqual, raises, late)) > > return v; > > > > will *not* find an existing variant when creating a method_type for #2, so we > > have to create a new one. > > > > But then we perform delayed parsing and call fixup_deferred_exception_variants > > for #1 and #2. f_d_e_v will replace TYPE_RAISES_EXCEPTIONS with the newly > > parsed noexcept-specifier. It also sets TYPE_CANONICAL (#2) to #1. Both > > noexcepts turned out to be the same, so now we have two equivalent variants in > > the list! I.e., > > > > +-----------------+ +-----------------+ +-----------------+ > > | main | | #2 | | #1 | > > | S S::(S*) |----->| S S::(S*) |----->| S S::(S*) |----->NULL > > | - | | noex(T::value) | | noex(T::value) | > > +-----------------+ +-----------------+ +-----------------+ > > > > Then we get to #3. As for #1 and #2, grokdeclarator calls build_memfn_type, > > which ends up calling build_cp_fntype_variant, which will use the loop > > above to look for an existing variant. The first one that matches > > cp_check_qualified_type will be used, so we use #2 rather than #1, and the > > TYPE_CANONICAL mismatch follows. Hopefully that makes sense. > > Why doesn't the TYPE_CANONICAL (v) == v check prevent this? In other words, I think you're asking: why did fixup_deferred_exception_variants set TYPE_CANONICAL (#2) to #1 (which then differs from TYPE_CANONICAL (#3), which is #2)? The method_type for #1 (I'll mark is as #1 here) is built with it being its own canonical type. The first call to fixup_deferred_exception_variants does not change it: in there, VARIANT is #1, the loop with 'TYPE_CANONICAL (v) == v' cannot find an existing variant that would match, so when we do v = build_cp_fntype_variant (TYPE_CANONICAL (variant), rqual, cr, false); we get #1 so TYPE_CANONICAL (variant) = v; is just TYPE_CANONICAL (#1) = #1; so no change. The second call to fixup_deferred_exception_variants: here we're working with VARIANT #2. Now we again scan the list of variants {main, #2, #1} where we find a match for #2: #1. #1's TYPE_CANONICAL is #1 as per above, so we set TYPE_CANONICAL (#2) = #1; which I think is correct. I think TYPE_CANONICAL (#3) should also be #1, not #2, which my patch attempts to do. Hope this explanation makes some sense, please ask away if it doesn't! > > As for the fix, I didn't think I could rewrite the method_type #2 with #1 > > because the type may have escaped via decltype. So my approach is to > > elide #2 from the list, so when looking for a matching variant, we always > > find #1 (#2 remains live though, which admittedly sounds sort of dodgy). > > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/11? > > > > PR c++/101715 > > > > gcc/cp/ChangeLog: > > > > * tree.c (fixup_deferred_exception_variants): Remove duplicate > > variants after parsing the exception specifications. > > > > gcc/testsuite/ChangeLog: > > > > * g++.dg/cpp0x/noexcept72.C: New test. > > * g++.dg/cpp0x/noexcept73.C: New test. > > --- > > gcc/cp/tree.c | 16 +++++++++++++++- > > gcc/testsuite/g++.dg/cpp0x/noexcept72.C | 21 +++++++++++++++++++++ > > gcc/testsuite/g++.dg/cpp0x/noexcept73.C | 13 +++++++++++++ > > 3 files changed, 49 insertions(+), 1 deletion(-) > > create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept72.C > > create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept73.C > > > > diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c > > index 7f7de86b4e8..2efad49e7c1 100644 > > --- a/gcc/cp/tree.c > > +++ b/gcc/cp/tree.c > > @@ -2804,8 +2804,9 @@ fixup_deferred_exception_variants (tree type, tree raises) > > /* Though sucky, this walk will process the canonical variants > > first. */ > > + tree prev = NULL_TREE; > > for (tree variant = TYPE_MAIN_VARIANT (type); > > - variant; variant = TYPE_NEXT_VARIANT (variant)) > > + variant; prev = variant, variant = TYPE_NEXT_VARIANT (variant)) > > if (TYPE_RAISES_EXCEPTIONS (variant) == original) > > { > > gcc_checking_assert (variant != TYPE_MAIN_VARIANT (type)); > > @@ -2827,6 +2828,19 @@ fixup_deferred_exception_variants (tree type, tree raises) > > v = build_cp_fntype_variant (TYPE_CANONICAL (variant), > > rqual, cr, false); > > TYPE_CANONICAL (variant) = v; > > + > > + /* If VARIANT became a duplicate (cp_check_qualified_type-wise) > > + of an existing variant in the variant list of TYPE after we > > + have parsed its exception specification, elide it. Otherwise, > > + build_cp_fntype_variant would use it, leading to "canonical > > + types differ for identical types." */ > > + for (v = TYPE_MAIN_VARIANT (type); v; v = TYPE_NEXT_VARIANT (v)) > > + if (v != variant > > + /* The main variant will not have TYPE_RAISES_EXCEPTIONS > > + so PREV should never be null. */ > > + && cp_check_qualified_type (v, variant, var_quals, > > + rqual, cr, false)) > > + TYPE_NEXT_VARIANT (prev) = TYPE_NEXT_VARIANT (variant); > > } > > else > > TYPE_RAISES_EXCEPTIONS (variant) = raises; > > diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept72.C b/gcc/testsuite/g++.dg/cpp0x/noexcept72.C > > new file mode 100644 > > index 00000000000..f1455b3b46b > > --- /dev/null > > +++ b/gcc/testsuite/g++.dg/cpp0x/noexcept72.C > > @@ -0,0 +1,21 @@ > > +// PR c++/101715 > > +// { dg-do compile { target c++11 } } > > + > > +template struct S { > > + S bar() noexcept(T::value); // #1 > > + S foo() noexcept(T::value); // #2 > > +}; > > + > > +template S S::foo() noexcept(T::value) {} // #3 > > + > > +template struct S2 { > > + S2 bar1() noexcept(T::value); > > + S2 bar2() noexcept(T::value); > > + S2 bar3() noexcept(T::value); > > + S2 bar4() noexcept(T::value); > > + S2 bar5() noexcept(T::value); > > + S2 baz() noexcept(T::value2); > > + S2 foo() noexcept(T::value); > > +}; > > + > > +template S2 S2::foo() noexcept(T::value) {} > > diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept73.C b/gcc/testsuite/g++.dg/cpp0x/noexcept73.C > > new file mode 100644 > > index 00000000000..24524f3592a > > --- /dev/null > > +++ b/gcc/testsuite/g++.dg/cpp0x/noexcept73.C > > @@ -0,0 +1,13 @@ > > +// PR c++/101715 > > +// { dg-do compile { target c++11 } } > > + > > +template struct S { }; > > + > > +template > > +struct A > > +{ > > + A& foo(A&&) noexcept((S::value)); > > + A& assign(A&&) noexcept((S::value)); > > +}; > > +template > > +A& A::foo(A&&) noexcept((S::value)) {} > > > > base-commit: 952b7dbb418198f86d7829aaf9d7f9fc7714a8b3 > Marek