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From "Shearer, Davin" <dshea...@novetta.com>
Subject Re: Qpid's move to CMake and effect on performance.
Date Mon, 27 Jan 2014 15:15:03 GMT
FYI -- by default rpmbuild strips symbols, effectively making Release and
RelWIthDebinfo the same thing.


On Mon, Jan 27, 2014 at 10:06 AM, Andrew Stitcher <astitcher@redhat.com>wrote:

> On Sat, 2014-01-25 at 16:05 +0000, Fraser Adams wrote:
>
> > ...
> > One of my colleagues mentioned to me that he reckons that there was a
> > performance drop off between (I think) 0.12 and 0.18 but I've got no
> > evidence other than anecdotal from him and certainly no reproducer.
>
> I doubt this has anything to do with the change of build system.
>
> >
> > It did get me thinking about CMake though (though my colleague insists
> > he was using automake so there might still be an issue).
> >
> > Am I correct in thinking that with CMake there are different "build
> > types" and that in "idiomatic" CMake usage it's "generally" via the use
> > of different build types that compiler optimisation flags get set?
>
> I think that (too lazy to actually go look) in autotools the build
> default was -O2 and the Fedora/RHEL packaging set -O3.
>
> It is completely true that with cmake we've opted to follow the usual
> cmake practice (which is standard on Windows too) of having the build
> configuration dictate the optimisation/debug flags. I think that in the
> Fedora/RHEL packages we now use the RelWithDebInfo build configuration
> which corresponds to -O2 -g.
>
> It is true that if you specify no CMAKE_BUILD_TYPE then you will get no
> optimisation or debug flags set which is perhaps a rather bad idea.
>
> What do you think the default build type should be? (Out of Debug = -g,
> Release = -O2 -DNDEBUG, RelWithDebInfo -O2 -DNDEBUG -g, MinSizeRel = -Os
> -DNDEBUG)
>
> It's not clear to me that we should prioritise performance over
> debugability in our default build.
>
> Andrew
>
>
>
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-- 
Davin Shearer
Engineer

8830 Stanford Blvd, Suite 306
Columbia, MD 21045

443-741-4517

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