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[69.125.73.58]) by smtp.gmail.com with ESMTPSA id y5sm9814917qkb.123.2020.03.22.14.14.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Mar 2020 14:14:40 -0700 (PDT) To: gcc-patches@gcc.gnu.org Subject: [PATCH] c++: Avoid a suspicious -Wnoexcept warning [PR93805] Date: Sun, 22 Mar 2020 17:14:38 -0400 Message-Id: <20200322211438.3303999-1-ppalka@redhat.com> X-Mailer: git-send-email 2.26.0.rc1.11.g30e9940356 MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-34.4 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, 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-Patchwork-Original-From: Patrick Palka via Gcc-patches From: "Li, Pan2 via Gcc-patches" Reply-To: Patrick Palka Errors-To: gcc-patches-bounces@gcc.gnu.org Sender: "Gcc-patches" In this PR we're emitting -Wnoexcept warnings about potentially-throwing NSDMIs when computing the noexcept specification of a class's defaulted default constructor. Alhough these warnings are in some sense valid, this patch takes the route of suppressing them, because: 1. the warning message is confusing in its current form; 2. warning for 'struct C { B b = B(); };' but not for 'struct C { B b; };' is inconsistent; and 3. emitting a warning here arguably doesn't fall under the umbrella of -Wnoexcept, whose documentation says it warns only when a noexcept-expression evaluates to false, but there are noexcept-expressions here. Tested on x86_64-pc-linux-gnu, does this look OK to commit? gcc/cp/ChangeLog: PR c++/93805 * method.c (walk_field_subobs): Pass tf_none as the complain argument to expr_noexcept_p. gcc/testsuite/ChangeLog: PR c++/93805 * g++.dg/warn/Wnoexcept2.C: New test. --- gcc/cp/method.c | 2 +- gcc/testsuite/g++.dg/warn/Wnoexcept2.C | 15 +++++++++++++++ 2 files changed, 16 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/warn/Wnoexcept2.C diff --git a/gcc/cp/method.c b/gcc/cp/method.c index c131fd41536..41b9ff86bdd 100644 --- a/gcc/cp/method.c +++ b/gcc/cp/method.c @@ -1988,7 +1988,7 @@ walk_field_subobs (tree fields, special_function_kind sfk, tree fnname, if (nsdmi == error_mark_node) *spec_p = error_mark_node; else if (*spec_p != error_mark_node - && !expr_noexcept_p (nsdmi, complain)) + && !expr_noexcept_p (nsdmi, tf_none)) *spec_p = noexcept_false_spec; } /* Don't do the normal processing. */ diff --git a/gcc/testsuite/g++.dg/warn/Wnoexcept2.C b/gcc/testsuite/g++.dg/warn/Wnoexcept2.C new file mode 100644 index 00000000000..60541be3575 --- /dev/null +++ b/gcc/testsuite/g++.dg/warn/Wnoexcept2.C @@ -0,0 +1,15 @@ +// PR c++/93805 +// { dg-do compile { target c++11 } } +// { dg-additional-options "-Wnoexcept" } + +struct B +{ + B() {} +}; + +struct C +{ + B b = B(); +}; + +C c; // { dg-bogus "noexcept-expression" }