[CMake] add_subdirectory and build directory

[Pierre-Julien Villoud]

Sorry I did not reply to you...

I actually use the target_link_libraries and the add_dependencies which is useless if using the target_link_libraries (I think ?)

So I really wonder why my objects are re-built... It's still a mystery for me !

Thanks again

Pierre-Julien VILLOUD

-----Message d'origine-----
De : Marcel Loose [mailto:loose at astron.nl] 
Envoyé : vendredi 11 septembre 2009 18:09
À : Pierre-Julien Villoud
Cc : cmake at cmake.org
Objet : Re: [CMake] add_subdirectory and build directory

Hi Pierre-Julien,

I think I see what the problem is. You didn't specify any dependencies.
You mention that project A depends on B. But don't you actually mean
that libA depends on libB? If that's the case you should add a
target_link_libraries(libA libB) to the CMakeLists.txt file of project
A.

Anyway, you may want to post your CMakeLists.txt files, so that people
can spot what you might be doing wrong. At the moment, I can only make
some wild guesses.

Best regards,
Marcel Loose.

On Fri, 2009-09-11 at 17:34 +0200, Pierre-Julien Villoud wrote:
> Hi and thanks for your answer...
> 
> Here is the ouput : 
> 
> I'm building A : My CMakelists.txt is in C:/A
> 
> -- Configuring done
> -- Generating done
> -- Build files have been written to: C:/A/Debug
> ==============Building A==============
> [  0%] Built target CMake
> Scanning dependencies of target B
> [  4%] Building CXX object C:/B/CMakeFiles/B.dir/B.cpp.obj
> Linking CXX static library C:\lib\libB.a
> [  4%] Built target B
> Linking CXX shared module C:\bin\A.dll
> [100%] Built target A
> 
> Then I'm building B : My CMakeLists.txt is in C:/B
> 
> -- Configuring done
> -- Generating done
> -- Build files have been written to: C:/B/Debug
> ==============Building B==============
> [  0%] Built target CMake
> Scanning dependencies of target B
> [100%] Building CXX object CMakeFiles/B.dir/B.cpp.obj
> Linking CXX static library C:\lib\libB.a
> [100%] Built target B
> 
> 
> Any clues ?
> 
> @Michael : I did not look at your long and precise answer (thank you very much for it BTW) but it seems quite complicated !! How are you managing your dependencies ?
> 
> Thank you for your help !
> 
> 
> 
> -----Message d'origine-----
> De : Marcel Loose [mailto:loose at astron.nl] 
> Envoyé : vendredi 11 septembre 2009 16:30
> À : Pierre-Julien Villoud
> Cc : cmake at cmake.org
> Objet : Re: [CMake] add_subdirectory and build directory
> 
> Hi Pierre-Julien,
> 
> Are you sure it's rebuilding? CMake (or 'make' actually), prints a lot
> of messages "Built target ..." even if no compilation was needed.
> However, if you also see messages like "Building ..." then it is
> actually rebuilding.
> 
> Without an example of the output of your build, it is hard to judge
> what, if anything, is going wrong.
> 
> Best regards,
> Marcel Loose.
> 
> On Fri, 2009-09-11 at 15:12 +0200, Pierre-Julien Villoud wrote:
> > Hi everyone, 
> > 
> >  
> > 
> > After unsuccessfully looking for an answer on Google, I contact you.
> > 
> > I have a question regarding the use of add_subdirectory. When a
> > project A is depending on a project B, I add the following in A's
> > CMakeLists.txt : 
> > 
> >  
> > 
> > Add_subdirectory(B Path/To/B/Build/Directory)
> > 
> >  
> > 
> > It does build B before A. But when I build B in its build directory
> > and I build A after, it builds B again whereas it should not since B
> > is up to date.
> > 
> >  
> > 
> > Anyone sees what's wrong ?
> > 
> >  
> > 
> > Thanks in advance
> > 
> >  
> > 
> > Pierre-Julien VILLOUD
> > 
> > 
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