From patchwork Thu Sep 16 22:05:55 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jonathan Wakely X-Patchwork-Id: 45096 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id C2079385741B for ; Thu, 16 Sep 2021 22:07:49 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C2079385741B DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1631830069; bh=FbgZ97+Zz8CFSpEurdhy+QR+MPFEx1DjEJSo7URl4Ug=; h=Date:To:Subject:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:From; b=tXmTJqewTf3/Re5WsPUh9bMj5oVS4UCx1nqDOHnEz+e90LEkAdV4gpx/UNC3vDsxy ne2U/mzxOdWVgkpIjMH5FKa4X46f/yNrByjDMlyoi2KT2OefrfjWO3k8f4OPZc2iBG /xNg0F81O2dUJP4VYi0FpoLKbajzcfMY9CSfB1tk= X-Original-To: gcc-patches@gcc.gnu.org Delivered-To: gcc-patches@gcc.gnu.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTP id 09CA73857000 for ; Thu, 16 Sep 2021 22:06:00 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 09CA73857000 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-458-o1qtaI1AOFqVBd7V9eOaXA-1; Thu, 16 Sep 2021 18:05:57 -0400 X-MC-Unique: o1qtaI1AOFqVBd7V9eOaXA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EC6451006AA2; Thu, 16 Sep 2021 22:05:56 +0000 (UTC) Received: from localhost (unknown [10.33.36.240]) by smtp.corp.redhat.com (Postfix) with ESMTP id 75AF312D4A; Thu, 16 Sep 2021 22:05:56 +0000 (UTC) Date: Thu, 16 Sep 2021 23:05:55 +0100 To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: [committed] libstdc++: Add noexcept to std::to_string overloads that don't allocate Message-ID: MIME-Version: 1.0 X-Clacks-Overhead: GNU Terry Pratchett X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-Spam-Status: No, score=-14.0 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_H2, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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: Jonathan Wakely via Gcc-patches From: Jonathan Wakely Reply-To: Jonathan Wakely Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Sender: "Gcc-patches" When the values is guaranteed to fit in the SSO buffer we know the string won't allocate, so the function can be noexcept. For 32-bit integers, we know they need no more than 9 bytes (or 10 with a minus sign) and the SSO buffer is 15 bytes. Signed-off-by: Jonathan Wakely libstdc++-v3/ChangeLog: * include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI] (to_string): Add noexcept if the type width is 32 bits or less. Tested x86_64-linux. Committed to trunk. commit 9d813ddd978aff75001d53fe55ff15e9167bb4d0 Author: Jonathan Wakely Date: Wed Sep 15 21:40:20 2021 libstdc++: Add noexcept to std::to_string overloads that don't allocate When the values is guaranteed to fit in the SSO buffer we know the string won't allocate, so the function can be noexcept. For 32-bit integers, we know they need no more than 9 bytes (or 10 with a minus sign) and the SSO buffer is 15 bytes. Signed-off-by: Jonathan Wakely libstdc++-v3/ChangeLog: * include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI] (to_string): Add noexcept if the type width is 32 bits or less. diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h index b61fe05efcf..24c454d863a 100644 --- a/libstdc++-v3/include/bits/basic_string.h +++ b/libstdc++-v3/include/bits/basic_string.h @@ -3718,6 +3718,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 inline string to_string(int __val) +#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_INT__) <= 32 + noexcept // any 32-bit value fits in the SSO buffer +#endif { const bool __neg = __val < 0; const unsigned __uval = __neg ? (unsigned)~__val + 1u : __val; @@ -3729,6 +3732,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 inline string to_string(unsigned __val) +#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_INT__) <= 32 + noexcept // any 32-bit value fits in the SSO buffer +#endif { string __str(__detail::__to_chars_len(__val), '\0'); __detail::__to_chars_10_impl(&__str[0], __str.size(), __val); @@ -3737,6 +3743,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 inline string to_string(long __val) +#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_LONG__) <= 32 + noexcept // any 32-bit value fits in the SSO buffer +#endif { const bool __neg = __val < 0; const unsigned long __uval = __neg ? (unsigned long)~__val + 1ul : __val; @@ -3748,6 +3757,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11 inline string to_string(unsigned long __val) +#if _GLIBCXX_USE_CXX11_ABI && (__CHAR_BIT__ * __SIZEOF_LONG__) <= 32 + noexcept // any 32-bit value fits in the SSO buffer +#endif { string __str(__detail::__to_chars_len(__val), '\0'); __detail::__to_chars_10_impl(&__str[0], __str.size(), __val);