[CMake] Parallel make & custom command

[Marcel Loose]

On Wed, 2011-06-29 at 23:43 +0200, Marcel Loose wrote:
> On Wed, 2011-06-29 at 20:46 +0200, Michael Wild wrote:
> > On 06/29/2011 05:22 PM, Marcel Loose wrote:
> > > Hi all,
> > > 
> > > I'm having a problem with a parallel 'make' where one or more
> sources
> > > are generated by a custom command.
> > > 
> > > The situation is as follows. There are a couple of targets
> (executables)
> > > that depend on the same source file being generated by a custom
> > > command. 
> > > 
> > > I notice that, when doing a parallel build, the custom command is
> > > executed multiple times, thereby potentially overwriting or
> corrupting
> > > the same file that's generated in different threads.
> > > 
> > > My feeling is that this is caused by the fact that CMake generates
a
> > > build.cmake file for each target separately. Hence, when doing a
> > > parallel build, these build.cmake files are also processed in
> parallel. 
> > > 
> > > Am I correct in this assumption? And if so, what's the proper
> solution
> > > for this problem?
> > > 
> > > Best regards,
> > > Marcel Loose.
> > > 
> > 
> > Yes, I've seen this issue too. The only way I can think of fixing
this
> > is by having a single custom target which depends on the generated
> > files, and then have the executables using the generated sources
> depend
> > on that custom target. This way you force the custom target to be
run
> > first before the other targets, thus avoiding the custom commands
> > generating the sources from running multiple times.
> > 
> > Michael
> > _______________________________________________
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> 
> Seems my webmail client completely screwed up the topic threading :-(
> Here's my reply again, hopefully now placed properly. Sorry for the
> noise.
> 
> After I had posted my question I realized that this issue has come up
> quite recently on the mailing list in a thread that I started -- see
> http://www.mail-archive.com/cmake@cmake.org/msg36362.html. Although
the
> original question was related to building mulitple targets in
parallel,
> Michael Hertling showed that CMake inherently has problems with
parallel
> builds when custom targets/commands come into play.
> 
> So maybe I should open an isse for this?
> 
> Best regards,
> Marcel Loose.
> 
> 
> _______________________________________________
> Powered by www.kitware.com
> 
> Visit other Kitware open-source projects at
http://www.kitware.com/opensource/opensource.html
> 
> Please keep messages on-topic and check the CMake FAQ at:
http://www.cmake.org/Wiki/CMake_FAQ
> 
> Follow this link to subscribe/unsubscribe:
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I've created an issue for this in the bug tracker:
http://public.kitware.com/Bug/view.php?id=12311

Regards,
Marcel Loose.