From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by sourceware.org (Postfix) with ESMTPS id 8CE943857C61 for ; Fri, 24 Jul 2020 12:42:59 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 8CE943857C61 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=tdevries@suse.de X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id BE25DAF73 for ; Fri, 24 Jul 2020 12:43:06 +0000 (UTC) Date: Fri, 24 Jul 2020 14:42:57 +0200 From: Tom de Vries To: gdb-patches@sourceware.org Subject: [PATCH][gdb/build] Fix Wmaybe-uninitialized in gdb_optional.h Message-ID: <20200724124255.GA14763@delia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-Spam-Status: No, score=-11.1 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, KAM_SHORT, RCVD_IN_MSPIKE_H3, 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: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 24 Jul 2020 12:43:01 -0000 Hi, When building with CFLAGS/CXXFLAGS="-O2 -g -Wall", we run into: ... In file included from src/gdb/exceptions.h:23, from src/gdb/utils.h:24, from src/gdb/defs.h:630, from src/gdb/record-btrace.c:22: src/gdb/ui-out.h: In function 'void btrace_insn_history(ui_out*, \ const btrace_thread_info*, const btrace_insn_iterator*, \ const btrace_insn_iterator*, gdb_disassembly_flags)': src/gdb/ui-out.h:352:18: warning: \ 'asm_list.ui_out_emit_type::m_uiout' may be used \ uninitialized in this function [-Wmaybe-uninitialized] 352 | m_uiout->end (Type); | ~~~~~~~~~~~~~^~~~~~ src/gdb/record-btrace.c:795:35: note: \ 'asm_list.ui_out_emit_type::m_uiout' was declared here 795 | gdb::optional asm_list; | ^~~~~~~~ ... This is reported as PR gcc/80635 - "[8/9/10/11 regression] std::optional and bogus -Wmaybe-uninitialized warning". Silence the warning by using the workaround suggested here ( https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80635#c53 ): ... union { struct { } m_dummy; T m_item; + volatile char dont_use; // Silences -Wmaybe-uninitialized warning. }; ... Build on x86_64-linux. Any comments? Thanks, - Tom [gdb/build] Fix Wmaybe-uninitialized in gdb_optional.h gdbsupport/ChangeLog: 2020-07-24 Tom de Vries PR build/26281 * gdb_optional.h (class optional): Add volatile member to union contaning m_dummy and m_item. --- gdbsupport/gdb_optional.h | 1 + 1 file changed, 1 insertion(+) diff --git a/gdbsupport/gdb_optional.h b/gdbsupport/gdb_optional.h index 02a87f6ee4..221b4f75b7 100644 --- a/gdbsupport/gdb_optional.h +++ b/gdbsupport/gdb_optional.h @@ -208,6 +208,7 @@ class optional { struct { } m_dummy; T m_item; + volatile char dont_use; // Silences -Wmaybe-uninitialized warning. }; /* True if the object was ever emplaced. */