From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roger Pau Monne Subject: Re: [PATCH] configure: Check for flex Date: Tue, 24 Apr 2012 17:35:36 +0100 Message-ID: <4F96D658.1050604@citrix.com> References: <1334515390-29941-1-git-send-email-jean.guyader@gmail.com> <115C65E3-769A-405D-A075-CB0D15AA6086@citrix.com> <20374.54254.482250.200623@mariner.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20374.54254.482250.200623@mariner.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Jackson Cc: "xen-devel@lists.xensource.com" , Jean Guyader List-Id: xen-devel@lists.xenproject.org Ian Jackson escribi=F3: > Roger Pau Monne writes ("Re: [Xen-devel] [PATCH] configure: Check for fle= x"): >> El 15/04/2012, a las 19:43, Jean Guyader escribi=F3: >>> libxl require the command flex to be present. >>> Verify in the configure script that the flex >>> command exsits. >>> >>> Signed-off-by: Jean Guyader >> >> I've already sent a patch for this, detecting and setting Flex and Bison= at configure, and printing a pretty error message if libxl needs them and = they are not found: >> >> http://lists.xen.org/archives/html/xen-devel/2012-04/msg00923.html > > (I'm afraid that patch is still in my (enormous) backlog, but:) > > I'm not very convinced that that patch is an improvement. All it > does, effectively, is change the error message from "flex: not found" > to a custom one which effectively says "I couldn't find flex". It also adds automatic detection of flex/bison from configure, so if the = user has those installed, and they are needed, the compilation will not = fail (without this patch the compilation will just fail). > If flex is not available, and the timestamps indicate the file needs > to be rebuilt, we have two choices, corresponding to two possible > situations: > 1. Assume that the problem is simply timestamp skew, and allow > the build to continue without regenerating the file (although > we should probably print a warning) > 2. Assume that the user has edited (or patched) the flex source > code, and stop with an error > > Of these I think 1. is preferable. In the latter case, if the user > edited it themselves they will hopefully be reading the make output > and see the warning; whereas if the user applied a patch, the patch > should update the flex output too. > > In practice we update these files rarely and of course we always > commit a corresponding change. So doing 1. will only adversely affect > a small minority of developers. Whereas doing 2. seems to cause > regular annoyance to many people who don't necessarily know what's > going on. > > Ian.