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 [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id C6C0F3858C74 for ; Thu, 12 Jan 2023 21:10:14 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org C6C0F3858C74 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673557814; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=0FPWuiZHUmAgScZsexn9rScn0wRQgaCfdXrkClPls5g=; b=a/3XwKOGUxisPK8gg4QyGD6ALLjJQ11gb7th939PpuU8oG4ijYYYKpCXTxKbW4IEdCinT3 K8SaLhWeeWaOLUCx9FuP5cJZw9EG/PjYP1uHSCRPQK/lBSbgJp2QPEHSrp50bG1SqBBXa+ dOH9N+RKnUa2rmIZvpTJj49oTJj2pIg= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-210-f1OL_ISTMtG18tZIsulcyQ-1; Thu, 12 Jan 2023 16:10:11 -0500 X-MC-Unique: f1OL_ISTMtG18tZIsulcyQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 3D1493811F3D; Thu, 12 Jan 2023 21:10:11 +0000 (UTC) Received: from localhost (unknown [10.33.36.192]) by smtp.corp.redhat.com (Postfix) with ESMTP id 007DD2166B26; Thu, 12 Jan 2023 21:10:10 +0000 (UTC) From: Jonathan Wakely To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Cc: Eric Botcazou , Jonathan Yong <10walls@gmail.com> Subject: [PATCH] libstdc++: Fix unintended layout change to std::basic_filebuf [PR108331] Date: Thu, 12 Jan 2023 21:10:10 +0000 Message-Id: <20230112211010.932966-1-jwakely@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-12.2 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_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Tested x86_64-linux. Bootstrapped x86_64-w64-mingw32 with both --enable-threads=posix and --enable-threads=win32. I need a libgcc or mingw maintainer to approve the gthr-win32.h part. OK for trunk? -- >8 -- GCC 13 has a new implementation of gthr-win32.h which supports C++11 mutexes, threads etc. but this causes an unintended ABI break. The __gthread_mutex_t type is always used in std::basic_filebuf even in C++98, so independent of whether C++11 sync primitives work or not. Because that type changed for the win32 thread model, we have a layout change in std::basic_filebuf. The member is completely unused, it just gets passed to the std::__basic_file constructor and ignored. So we don't need that mutex to actually work, we just need its layout to not change. Introduce a new __gthr_win32_legacy_mutex_t struct in gthr-win32.h with the old layout, and conditionally use that in std::basic_filebuf. PR libstdc++/108331 libgcc/ChangeLog: * config/i386/gthr-win32.h (__gthr_win32_legacy_mutex_t): New struct matching the previous __gthread_mutex_t struct. (__GTHREAD_LEGACY_MUTEX_T): Define. libstdc++-v3/ChangeLog: * config/io/c_io_stdio.h (__c_lock): Define as a typedef for __GTHREAD_LEGACY_MUTEX_T if defined. --- libgcc/config/i386/gthr-win32.h | 8 ++++++++ libstdc++-v3/config/io/c_io_stdio.h | 7 +++++++ 2 files changed, 15 insertions(+) diff --git a/libgcc/config/i386/gthr-win32.h b/libgcc/config/i386/gthr-win32.h index 146357fa436..050c7a21fcc 100644 --- a/libgcc/config/i386/gthr-win32.h +++ b/libgcc/config/i386/gthr-win32.h @@ -381,6 +381,14 @@ typedef struct timespec __gthread_time_t; #define __GTHREAD_COND_INIT_FUNCTION __gthread_cond_init_function #define __GTHREAD_TIME_INIT {0, 0} +// Libstdc++ std::basic_filebuf needs the old definition of __gthread_mutex_t +// for layout purposes, but doesn't actually use it. +typedef struct { + long __unused1; + void *__unused2; +} __gthr_win32_legacy_mutex_t; +#define __GTHREAD_LEGACY_MUTEX_T __gthr_win32_legacy_mutex_t + #if defined (_WIN32) && !defined(__CYGWIN__) #define MINGW32_SUPPORTS_MT_EH 1 /* Mingw runtime >= v0.3 provides a magic variable that is set to nonzero diff --git a/libstdc++-v3/config/io/c_io_stdio.h b/libstdc++-v3/config/io/c_io_stdio.h index 1a5e05a844a..e9e6e3ef4d8 100644 --- a/libstdc++-v3/config/io/c_io_stdio.h +++ b/libstdc++-v3/config/io/c_io_stdio.h @@ -39,7 +39,14 @@ namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION +#ifdef __GTHREAD_LEGACY_MUTEX_T + // The layout of __gthread_mutex_t changed in GCC 13, but libstdc++ doesn't + // actually use the basic_filebuf::_M_lock member, so define it consistently + // with the old __gthread_mutex_t to avoid an unnecessary layout change: + typedef __GTHREAD_LEGACY_MUTEX_T __c_lock; +#else typedef __gthread_mutex_t __c_lock; +#endif // for basic_file.h typedef FILE __c_file; -- 2.39.0