From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH] libxl/Makefile: Don't optimize debug builds; add macro debugging information Date: Mon, 1 Dec 2014 12:12:48 +0000 Message-ID: <1417435968.29138.19.camel@citrix.com> References: <1417430384-26220-1-git-send-email-euan.harris@citrix.com> <1417434193.29138.14.camel@citrix.com> <20141201115521.GB3731@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20141201115521.GB3731@citrix.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: Euan Harris Cc: Ian.Jackson@eu.citrix.com, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On Mon, 2014-12-01 at 11:55 +0000, Euan Harris wrote: > On Mon, Dec 01, 2014 at 11:43:13AM +0000, Ian Campbell wrote: > > On Mon, 2014-12-01 at 10:39 +0000, Euan Harris wrote: > > > libxl debug builds are built with optimization level -O1, inherited from > > > the CFLAGS definition in StdGNU.mk. Optimizations confuse the debugger, > > > and the comment justifying -O1 in StdGNU.mk should not apply for a > > > userspace library. Disable optimization by appending -O0 to CFLAGS, > > > which overrides the -O1 flag specified earlier. > > > > I think if this argument applies (I see no reason to disagree) then it > > should apply to the whole of tools/* or at least to tools/lib* and not > > just to libxl. IOW this probably belongs at a higher level somewhere. > > Ok, I'll submit a new patch putting it in tools/Rules.mk Thanks. > > > Also specify -g3, to add macro debugging information which allows > > > gdb to expand macro invocations. This is useful as libxl uses many > > > non-trivial macros. > > > > Useful, I'd never heard of this. Do you know which version of gcc > > introduced it? (AKA do we need to make it part of configure.ac to check > > availability or not). > > It's documented in GCC 2.95.3 [1], which is as far back as the online > manuals go. > > [1] https://gcc.gnu.org/onlinedocs/gcc-2.95.3/gcc_2.html#SEC9 OK, I'm pretty sure that's (way....) before our cut-off. Thanks. > > Not sure if you were proposing this change for 4.5 or not. > > It would be nice to have, but I was assuming that 4.5 was more or less > closed by now. Exceptions can be asked/argued for. I'd be a bit wary of something like this since the knock-on effects might be a bit subtle. Completely fine during a dev window though. Ian.