From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12774 invoked by alias); 25 May 2018 13:41:00 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 12734 invoked by uid 89); 25 May 2018 13:41:00 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.4 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy=autoconf, management X-HELO: mail-oi0-f68.google.com Received: from mail-oi0-f68.google.com (HELO mail-oi0-f68.google.com) (209.85.218.68) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Fri, 25 May 2018 13:40:58 +0000 Received: by mail-oi0-f68.google.com with SMTP id v2-v6so4600564oif.3 for ; Fri, 25 May 2018 06:40:58 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=1bS3LMQirkm5oxXE7AcoNfYYJ8afE1Gzlnfs3Z6ITxQ=; b=LKBtKt4XZ4gVuXPHejBm6Z/o9EEOrL5g1TVS9Fnf8KBLf+ypWYSY8f/72+b9FM1TNf S72M6WV0AHRIMoM3cGtHQm2FSBc5+6L0Ee11GHyyYestsESsdu7L4Uuz07+FPCxLEchq zxn+VYSrllI1vc/qVrBEBEnJ5d+rATL6+ptqhTOhgmj5gDvvpHcCW9Vq0HaXKMV8FhYY xv4S2VWEr39VDG1h5dVc2EWshcUPFG9TpwevNi9ySCKbOY6vnQY5qOircRUZDhzl8sbO TuWTRdz/NW0ykwRnpAG0noY3MY4OkmSpopI0vPAumo2aU4+NE14326iAqc9PP4Xe0t5W ae6w== X-Gm-Message-State: ALKqPweEu+9qRCb0oj9/M5TJz3bHrMDF4p4DdI3s7VHg88e0OKCoSzxC THU55hm6am0tk7GeVPLJvQyuPTHvw9TL4g//64LFOQ== X-Google-Smtp-Source: ADUXVKLsUcJdergxm5moFw8QesdkUu2MFicodvhWeRHr1X8RukAASkmErYqpONhAsiouS7P1nNl02He4rtgzfaS4O0U= X-Received: by 2002:aca:a906:: with SMTP id s6-v6mr1404763oie.101.1527255656809; Fri, 25 May 2018 06:40:56 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a9d:2cb8:0:0:0:0:0 with HTTP; Fri, 25 May 2018 06:40:55 -0700 (PDT) In-Reply-To: <12da5584-932c-c277-5d1a-51ed5fc57b97@redhat.com> References: <20180512140025.5957-1-slyfox@inbox.ru> <12da5584-932c-c277-5d1a-51ed5fc57b97@redhat.com> From: Eric Gallager Date: Fri, 25 May 2018 14:02:00 -0000 Message-ID: Subject: Re: [PATCH] gcc/configure.ac: add --disable-systemtap switch To: Jeff Law Cc: Sergei Trofimovich , Gcc Patch List , Sergei Trofimovich Content-Type: text/plain; charset="UTF-8" X-IsSubscribed: yes X-SW-Source: 2018-05/txt/msg01504.txt.bz2 On 5/24/18, Jeff Law wrote: > On 05/12/2018 08:00 AM, Sergei Trofimovich via gcc-patches wrote: >> From: Sergei Trofimovich >> >> Before the change systemtap probes were enabled >> if target headers had sys/sdt.h at ./configure time. >> >> After the change explicitly ask to enable or disable >> for probe support and not rely on automagic dependency >> discovery. > I'm not terribly concerned about the uninstalling systemtap while > compiling gcc problem. That seems like a package management problem on > the distro side. > > 61257 does raise the issue of header file usability which is a much > bigger concern. c#1 indicates autoconf-2.70 introduces code which > instead of testing for header file existence instead checks for > usability. So I'd rather see us moving towards making that happen > rather than explicit enable/disable of systemtap headers/probes. > > jeff > I retracted c#1 in c#4. What autoconf-2.70 changes is how the AC_CHECK_HEADERS macro is expanded. In current versions of autoconf, AC_CHECK_HEADERS checks for header file usability, presence, and existence, but allows the latter 2 to override the usability check. In autoconf-2.70, however, AC_CHECK_HEADERS will *only* do the usability check. However, after looking at the code in question, I found that AC_CHECK_HEADERS is not even used here, but rather it just does `test -f`. Thus the autoconf-2.70 changes won't automatically fix anything, since `test -f` is at the shellcode level rather than the m4 level. So we don't need to wait for it to be released, and probably shouldn't anyways, considering how many years its release has been pending. Eric