From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 10175 invoked by alias); 30 Aug 2018 02:31:27 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 9794 invoked by uid 89); 30 Aug 2018 02:31:09 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-2.9 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy= X-HELO: gateway30.websitewelcome.com Received: from gateway30.websitewelcome.com (HELO gateway30.websitewelcome.com) (192.185.149.4) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 30 Aug 2018 02:31:07 +0000 Received: from cm10.websitewelcome.com (cm10.websitewelcome.com [100.42.49.4]) by gateway30.websitewelcome.com (Postfix) with ESMTP id 868A7CB47 for ; Wed, 29 Aug 2018 21:31:06 -0500 (CDT) Received: from box5379.bluehost.com ([162.241.216.53]) by cmsmtp with SMTP id vCjQfi6YWBcCXvCjbfCBxL; Wed, 29 Aug 2018 21:31:06 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=tromey.com; s=default; h=Content-Type:MIME-Version:Message-ID:In-Reply-To:Date: References:Subject:Cc:To:From:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=8UcRNywb5Fm7fykxYQxh76LzJfCkuR3W/YQGtIENuGQ=; b=NlKu3U5Z2AwIJ275k8tOLiW4SJ yRmQYhvRCL52yIcXrd9YPbT5RrJdJ8YpUtjGIl3UH3R/UwevUFLiFjaap/WbEAIfn9srrlB+YTUaE EaTSp19Sbg7yhTL4gw4CbgTsu; Received: from 75-166-85-72.hlrn.qwest.net ([75.166.85.72]:49690 helo=bapiya) by box5379.bluehost.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1fvCjQ-000PCz-Br; Wed, 29 Aug 2018 21:30:48 -0500 From: Tom Tromey To: Palmer Dabbelt Cc: andrew.burgess@embecosm.com, gdb-patches@sourceware.org Subject: Re: [PATCH] gdb: Ensure compiler doesn't optimise variable out in test References: <20180829180259.2718-1-andrew.burgess@embecosm.com> Date: Thu, 30 Aug 2018 02:31:00 -0000 In-Reply-To: (Palmer Dabbelt's message of "Wed, 29 Aug 2018 17:21:58 -0700 (PDT)") Message-ID: <87in3svb54.fsf@tromey.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-SW-Source: 2018-08/txt/msg00799.txt.bz2 >>>>> "Palmer" == Palmer Dabbelt writes: Palmer> Isn't the compiler still free to kill "a" here because it can see into Palmer> use_a() and therefor inline it? I'd expected it to choose to inline Palmer> use_a(), as doing nothing is always cheaper than calling a function. It is but in practice gdb compiles without optimization in most cases and compilers generally don't bother in that situation. Though if there's a readily available, more principled fix, that would be fine too. Tom