From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 112729 invoked by alias); 6 Aug 2015 14:54:44 -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 112644 invoked by uid 89); 6 Aug 2015 14:54:44 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.4 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=no version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Thu, 06 Aug 2015 14:54:43 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id 037B1A58AD; Thu, 6 Aug 2015 14:54:42 +0000 (UTC) Received: from [127.0.0.1] (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t76ET5Bk010273; Thu, 6 Aug 2015 10:29:06 -0400 Message-ID: <55C36F31.5080807@redhat.com> Date: Thu, 06 Aug 2015 14:54:00 -0000 From: Pedro Alves User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: "Metzger, Markus T" CC: "gdb-patches@sourceware.org" Subject: Re: [PATCH] configure: check for perf_event.h version References: <1438866405-22616-1-git-send-email-markus.t.metzger@intel.com> <55C365B2.4010906@redhat.com> In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SW-Source: 2015-08/txt/msg00153.txt.bz2 On 08/06/2015 03:14 PM, Metzger, Markus T wrote: >> -----Original Message----- >> From: Pedro Alves [mailto:palves@redhat.com] >> Sent: Thursday, August 6, 2015 3:49 PM >> To: Metzger, Markus T >> Cc: gdb-patches@sourceware.org >> Subject: Re: [PATCH] configure: check for perf_event.h version >> >> On 08/06/2015 02:06 PM, Markus Metzger wrote: >>> Intel(R) Processor Trace support requires a recent linux/perf_event.h >> header. >>> >>> When GDB is built on an older system, Intel(R) Processor Trace will not be >>> available and there is no indication in the configure and build log as to >>> what went wrong. >>> >>> Check for a compatible linux/perf_event.h at configure-time. >> >> >>> diff --git a/gdb/configure.ac b/gdb/configure.ac >>> index 905c27b..d867e85 100644 >>> --- a/gdb/configure.ac >>> +++ b/gdb/configure.ac >>> @@ -1252,6 +1252,20 @@ if test "${with_intel_pt}" = no; then >>> AC_MSG_WARN([Intel(R) Processor Trace support disabled; some >> features may be unavailable.]) >>> HAVE_LIBIPT=no >>> else >>> + AC_PREPROC_IFELSE(AC_LANG_SOURCE([[ >>> +#include >>> +#ifdef PERF_ATTR_SIZE_VER5 >>> +# error >>> +#endif >> >> Can you explain what kind of symbol PERF_ATTR_SIZE_VER5 is? >> From the patch, I understand that that is something that is _not_ >> defined in the perf versions that are supposedly supported? >> (otherwise, I'd expect an #ifndef instead.) > > It's a macro. Was there ever a PERF_ATTR_SIZE_VER4 symbol? What if PERF_ATTR_SIZE_VER6 is ever created? Do we want to have to check for it explicitly then? > I took the double-negation approach from a similar > check for python_has_threads. In the python case, we've already checked earlier that python.h is available. In your case, it seems that if isn't available, you end up with perf_event=yes? Is that what we want? > Maybe this wasn't such a good idea. Note also that the Python code has an explicit comment to help people not get confused with the negation: # Note that the test is reversed so that python_has_threads=yes on # unexpected failures. If this goes with the double-negation approach, a similar comment would be very nice to have. Thanks, Pedro Alves