From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from rock.gnat.com (rock.gnat.com [205.232.38.15]) by sourceware.org (Postfix) with ESMTPS id 88BAD3858D37; Fri, 3 Mar 2023 20:57:23 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 88BAD3858D37 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=adacore.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=adacore.com Received: from localhost (localhost.localdomain [127.0.0.1]) by filtered-rock.gnat.com (Postfix) with ESMTP id 5051A116597; Fri, 3 Mar 2023 15:57:23 -0500 (EST) X-Virus-Scanned: Debian amavisd-new at gnat.com Received: from rock.gnat.com ([127.0.0.1]) by localhost (rock.gnat.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id itTWNyPJdwwY; Fri, 3 Mar 2023 15:57:23 -0500 (EST) Received: from free.home (tron.gnat.com [IPv6:2620:20:4000:0:46a8:42ff:fe0e:e294]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by rock.gnat.com (Postfix) with ESMTPS id D5137116590; Fri, 3 Mar 2023 15:57:22 -0500 (EST) Received: from livre (livre.home [172.31.160.2]) by free.home (8.15.2/8.15.2) with ESMTPS id 323KvDxt611619 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Fri, 3 Mar 2023 17:57:15 -0300 From: Alexandre Oliva To: Florian Weimer Cc: Alexandre Oliva via Gcc-patches , Jonathan Wakely , Jonathan Wakely , "libstdc++" , Bernd Edlinger Subject: Re: [libstdc++] Use __gthread_join in jthread/95989 Organization: Free thinker, does not speak for AdaCore References: <87ttz1r3qm.fsf@mid.deneb.enyo.de> Errors-To: aoliva@lxoliva.fsfla.org Date: Fri, 03 Mar 2023 17:57:13 -0300 In-Reply-To: (Alexandre Oliva's message of "Fri, 03 Mar 2023 17:36:31 -0300") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.84 X-Spam-Status: No, score=-6.0 required=5.0 tests=BAYES_00,KAM_DMARC_STATUS,KAM_NUMSUBJECT,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Mar 3, 2023, Alexandre Oliva wrote: > Hello, Florian, > On Mar 3, 2023, Florian Weimer wrote: >> * Alexandre Oliva via Gcc-patches: >>> + // Make sure it's not optimized out, not even with LTO. >>> + asm ("" : : "rm" (depend)); >> If the m constraint is used, this may never emit the symbol name and >> thus not create a reference after all. > But that is no longer the pthread symbol itself, it's the symbol of a > static member function with vague linkage that, because the compiler > believes the asm statement will reference it, will still be output, and > it's that function body that will refer to and thus pull in the symbols > we need. > Now, hmm, maybe with per-function sections, the compiler will emit it, > but with section gc, the linker may drop it, so we might lose the needed > function body. When performing LTO with an LTO-enabled libstdc++. Wait, no, you had me going but it's really fine. What would be in memory is a *pointer* to the function, so the function would still be referenced by whatever initialized the pointer, so it wouldn't get GCed. -- Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/ Free Software Activist GNU Toolchain Engineer Disinformation flourishes because many people care deeply about injustice but very few check the facts. Ask me about