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Subject: Re: Review Request 26426: Add --enable-debug flag to ./configure for
 controlling emission of debug information
From: "Timothy St. Clair" <tstclair@redhat.com>
To: "Timothy St. Clair" <tstclair@redhat.com>,
 "Benjamin Hindman" <benh@berkeley.edu>
Cc: "mesos" <dev@mesos.apache.org>, "Cody Maloney" <cody@mesosphere.io>
Date: Wed, 15 Oct 2014 01:30:47 -0000
Message-ID: <20141015013047.24414.95512@reviews.apache.org>
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Reply-To: "Timothy St. Clair" <tstclair@redhat.com>

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> On Oct. 14, 2014, 9:06 p.m., Timothy St. Clair wrote:
> > configure.ac, line 281
> > <https://reviews.apache.org/r/26426/diff/1/?file=714874#file714874line281>
> >
> >     Is there a reason you want to leave debug symbols out of optimized builds?  
> >     
> >     cmake has the pattern correct imho: 
> >     Release
> >     Debug
> >     ReleaseWithDebug
> >     
> >     A ReleaseWithDebug allows packagers, such as myself, to build w/debugsymbols that are stripped out into a .debuginfo package which can be used by developers for tracing "When bears attack".  Granted that it is tenuous debugging at best, but it's better then nothing. 
> >     
> >     So I think we want all three modes, stripping all debug information is not really idea.
> 
> Cody Maloney wrote:
>     My main motivation is to shrink the size of libmesos. Yesterday sugis in #mesos had one which was 213M. For the buildbot internally, full debian packages (which are compressed) of mesos weign in at 165M a piece (Yes, stripping post-build would help a lot, but why build it to begin with?). Most of this is debug info. Also, we build a bunch of different ways, and when libmesos is as big as it is, a decent amount of time ends up being spent on disk I/O reading / writing all the debug info when we are really just trying to ensure it builds on all the different platforms (Not to mention storage and file size shipping things around the network to centralized repositories).
>     
>     The simple toggle between debug and release, removing the legacy logic gets us most of the benefit.
>     
>     If you have a good place to point me for what is needed to get a 'ReleaseWithDebug' info build up and running I can definitely work on adding that as well.
> 
> Cody Maloney wrote:
>     It is also entirely possible to specify custom CXXFLAGS + CFLAGS with this patch to get the old "optimized debug" build. The flags set by --enable-debug (or not having it), to get back the "optimized debug" build from before.

I suppose rpm builds default CXXFLAGS to '-O2 -g ...', so I can buy the argument of just making it easier on the average person.


- Timothy


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On Oct. 14, 2014, 11:07 p.m., Cody Maloney wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/26426/
> -----------------------------------------------------------
> 
> (Updated Oct. 14, 2014, 11:07 p.m.)
> 
> 
> Review request for mesos, Benjamin Hindman and Timothy St. Clair.
> 
> 
> Repository: mesos-git
> 
> 
> Description
> -------
> 
> Reworks building mesos in "debug" vs. "release". By default, mesos is now built in release (no debug info, optimized build). If '--enable-debug' is specified to configure, than optimization will be turned off, and debug info will be turned on.
> 
> This also adds a variable 'DEBUG' to the build environment, which people can use in code to see if mesos is built with debugging to enable extra assertions / checks. For release builds we may want to set 'NDEBUG' which removes assert()'s, but that is a seperate discussion.
> 
> Main benefits:
> 1) Getting a build to include/exclude debug information at will is feasible. Before some things like using clang would forcibly enable debug info in all cases
> 2) libmesos.so and the other binaries which get packaged up for use in distributions shrink considerably without manually stripping post-build (Improves build time, makes packaging cleaner)
> 
> 
> Diffs
> -----
> 
>   configure.ac 2b372e06006250b5230956ef096473e98f3fa590 
> 
> Diff: https://reviews.apache.org/r/26426/diff/
> 
> 
> Testing
> -------
> 
> Built with both --enable-debug and without, checking that the flags get passed through correctly.
> 
> 
> Thanks,
> 
> Cody Maloney
> 
>


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