From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.ziglang.org (mail.ziglang.org [108.61.23.47]) by sourceware.org (Postfix) with ESMTPS id 1F0113858D28 for ; Sat, 29 Jan 2022 04:04:05 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 1F0113858D28 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=ziglang.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=ziglang.org Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ziglang.org; s=mail; t=1643429042; bh=cP0vhnlsFTVazltzwEUnCapsJS764wYtRGV+rQsMOl0=; h=Date:To:Cc:References:From:Subject:In-Reply-To; b=hb1thDVnSJ/lxKQyce7fmCBoNAsNIGYk5ukxnztJE+d7qx9eghGSHtvOBFqfz/XDq yAXFkVCej+kjQJOqD83TlYDcAIp8MvX1QkA+BqUsibyFu+XiKzobkRDPONmS21x/ZC 8N4BwTSj97tm4i2uhO2D4I+b+Cq8Zyjvuy9lHuf8= Date: Fri, 28 Jan 2022 21:04:01 -0700 MIME-Version: 1.0 Content-Language: en-US To: "H.J. Lu" Cc: GNU C Library References: <20220129023727.1496360-1-andrew@ziglang.org> From: Andrew Kelley Subject: Re: [PATCH] features: version-gate _DYNAMIC_STACK_SIZE_SOURCE In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-12.5 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE 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: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 29 Jan 2022 04:04:07 -0000 On 1/28/22 20:00, H.J. Lu wrote: > On Fri, Jan 28, 2022 at 6:38 PM Andrew Kelley wrote: >> >> Without this patch, software compiled against glibc 2.34 headers but >> then executed on a system with an older glibc version will attempt to >> invoke `sysconf(_SC_SIGSTKSZ)` when MINSIGSTKSZ or SIGSTKSZ are used. On >> glibcs older than 2.34, this will return -1 (with an errno of EINVAL), >> effectively causing MINSIGSTKSZ and SIGSTKSZ to have the value of -1. >> >> This patch version-gates the _DYNAMIC_STACK_SIZE_SOURCE preprocessor >> definition so that this problem cannot occur. >> >> Downstream patch: >> https://github.com/ziglang/zig/commit/39083c31a550ed80f369f60d35791e98904b8096 >> --- >> include/features.h | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/include/features.h b/include/features.h >> index ab2b2caac4..77a8f8cc32 100644 >> --- a/include/features.h >> +++ b/include/features.h >> @@ -220,8 +220,10 @@ >> # define _DEFAULT_SOURCE 1 >> # undef _ATFILE_SOURCE >> # define _ATFILE_SOURCE 1 >> -# undef _DYNAMIC_STACK_SIZE_SOURCE >> -# define _DYNAMIC_STACK_SIZE_SOURCE 1 >> +# if __GNUC_PREREQ (2,34) >> +# undef _DYNAMIC_STACK_SIZE_SOURCE >> +# define _DYNAMIC_STACK_SIZE_SOURCE 1 > > You are changing a glibc 2.35 header file. Isn't __GNUC_PREREQ (2,34) > always true? Am I missing something? You are correct. Downstream we also have a patch that removes the __GLIBC_MINOR__ preprocessor definition. Instead, we pass it on the command line. https://github.com/ziglang/zig/commit/4d48948b526337947ef59a83f7dbc81b70aa5723 The Zig project aims to support targeting many versions of glibc; not only the latest one. Our strategy is multi-faceted. For the shared objects, there is this project: https://github.com/ziglang/glibc-abi-tool/ And then we have the headers. For the most part, the latest glibc headers are still correct for targeting systems with older glibc versions. Some of the other usages of __GNUC_PREREQ look to be supporting this use case to me. An occasional patch such as this one is needed to make it work correctly, however. I can understand there would be hesitation to support such a use case. I hope that glibc maintainers would consider it however, because ultimately it is helping glibc users cross-compile, targeting their production systems from their development machines. Thanks for your time. > >> +# endif >> #endif >> >> /* If nothing (other than _GNU_SOURCE and _DEFAULT_SOURCE) is defined, >> -- >> 2.33.1 >> > >