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[209.6.216.142]) by smtp.gmail.com with ESMTPSA id a63sm4871488qkf.132.2021.05.07.09.10.21 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 May 2021 09:10:21 -0700 (PDT) To: gcc-patches@gcc.gnu.org Subject: [pushed] c++: reject class lvalues in 'rvalue' Date: Fri, 7 May 2021 12:10:19 -0400 Message-Id: <20210507161019.4126183-1-jason@redhat.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-15.7 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_H4, 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-Patchwork-Original-From: Jason Merrill via Gcc-patches From: Jason Merrill Reply-To: Jason Merrill Errors-To: gcc-patches-bounces@gcc.gnu.org Sender: "Gcc-patches" Wrapping a class lvalue in NON_LVALUE_EXPR is not sufficient to make it a usable prvalue; callers must use force_rvalue instead. Tested x86_64-pc-linux-gnu, applying to trunk. gcc/cp/ChangeLog: * tree.c (rvalue): Assert expr is not a class lvalue. --- gcc/cp/tree.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) base-commit: fc178519771db508c03611cff4a1466cf67fce1d diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c index 4ccd7a314f5..7f148b4b158 100644 --- a/gcc/cp/tree.c +++ b/gcc/cp/tree.c @@ -940,7 +940,12 @@ rvalue (tree expr) /* We need to do this for rvalue refs as well to get the right answer from decltype; see c++/36628. */ if (!processing_template_decl && glvalue_p (expr)) - expr = build1 (NON_LVALUE_EXPR, type, expr); + { + /* But don't use this function for class lvalues; use move (to treat an + lvalue as an xvalue) or force_rvalue (to make a prvalue copy). */ + gcc_checking_assert (!CLASS_TYPE_P (type)); + expr = build1 (NON_LVALUE_EXPR, type, expr); + } else if (type != TREE_TYPE (expr)) expr = build_nop (type, expr);