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 2107838515C1 for ; Tue, 28 Mar 2023 20:15:04 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 2107838515C1 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=1680034503; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=DRyGQUFnr41Xt9zmq8fVAJ3d2/mJ9U6HV1Qxy7gy6lA=; b=EZ0D2TQ7xfXzDuaO3azQDVs1iDNhFMSU8TFw8HzQm53RHtAYU0H0GkNp3piVsnjH9gYlxR QszYQV8hxp6DjtSIChdf6jX2UlQ6IT7kJOvYcwfcAOF2TthhO3ayVle1Smpj39IC6b+SJb giNDqBp4zk0Av6W16XcNHvPOeg065TA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-658-USyRtZ5YON-hoC5XWDyx2g-1; Tue, 28 Mar 2023 16:15:02 -0400 X-MC-Unique: USyRtZ5YON-hoC5XWDyx2g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id F0FDA801210; Tue, 28 Mar 2023 20:15:01 +0000 (UTC) Received: from localhost (unknown [10.33.36.149]) by smtp.corp.redhat.com (Postfix) with ESMTP id B65B51402C08; Tue, 28 Mar 2023 20:15:01 +0000 (UTC) From: Jonathan Wakely To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: [committed] libstdc++: More fixes for null pointers used with std::char_traits Date: Tue, 28 Mar 2023 21:15:01 +0100 Message-Id: <20230328201501.1202700-1-jwakely@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-11.8 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_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham 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 powerpc64le-linux. Pushed to trunk. -- >8 -- The std::char_traits member functions require that [p,p+n) is a valid range, which is true for p==nullptr iff n==0. But we must not call memcpy, memset etc, in that case, as they require non-null pointers even when n==0. This std::char_traits and std::char_traits explicit specializations are already correct, but the primary template has some bugs. libstdc++-v3/ChangeLog: * include/bits/char_traits.h (char_traits::copy): Return without using memcpy if n==0. (char_traits::assign): Likewise for memset. --- libstdc++-v3/include/bits/char_traits.h | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/libstdc++-v3/include/bits/char_traits.h b/libstdc++-v3/include/bits/char_traits.h index cfc7d0f0e14..68ed827f982 100644 --- a/libstdc++-v3/include/bits/char_traits.h +++ b/libstdc++-v3/include/bits/char_traits.h @@ -263,6 +263,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION char_traits<_CharT>:: copy(char_type* __s1, const char_type* __s2, std::size_t __n) { + if (__n == 0) + return __s1; #if __cplusplus >= 202002L if (std::__is_constant_evaluated()) { @@ -271,7 +273,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION return __s1; } #endif - __builtin_memcpy(__s1, __s2, __n * sizeof(char_type)); return __s1; } @@ -293,9 +294,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION if _GLIBCXX17_CONSTEXPR (sizeof(_CharT) == 1 && __is_trivial(_CharT)) { - unsigned char __c; - __builtin_memcpy(&__c, __builtin_addressof(__a), 1); - __builtin_memset(__s, __c, __n); + if (__n) + { + unsigned char __c; + __builtin_memcpy(&__c, __builtin_addressof(__a), 1); + __builtin_memset(__s, __c, __n); + } } else { -- 2.39.2