[CMake] add_subdirectory and build directory

Tue Sep 15 04:16:55 EDT 2009

I found my problem

Here are 2 CMakeLists.txt : 

===================================
CMakeLists.txt : libMaths : 

#Minimum Cmake version required
cmake_minimum_required(VERSION 2.6)

add_library(Maths
	MathFuncsLib.cpp
)
===================================

===================================
CMakeLists.txt : HelloMath : 

#Minimum Cmake version required
cmake_minimum_required(VERSION 2.6)

include_directories(../Math)

link_directories(../Math)

add_executable(HelloMath
	hellomath.cpp
)

target_link_libraries(HelloMath
	Maths
)	

add_subdirectory(../Math ../Math)
===================================

My build process is the following : 
Cmake (...) && make

And it's the cmake call that causes the problem : 

In C:\Maths : 
> Cmake -G"MinGW Makefiles" -DCMAKE_BUILD_TYPE=Release && make => builds libMaths

In C:\HelloMath : 
> Cmake -G"MinGW Makefiles" -DCMAKE_BUILD_TYPE=Release && make => builds HelloMath AND builds libMaths (whereas it's up to date) because of the cmake call.

The following works : 
In C:\HelloMath : 
> Cmake -G"MinGW Makefiles" -DCMAKE_BUILD_TYPE=Release && make => builds HelloMath AND builds libMaths because of the cmake call.

In C:\Maths : 
> make => does not build libMaths since it's up to date.

So I must try to remove the cmake call and it will be fine !

Sorry to have bothered you...

Thanks !

Pierre-Julien VILLOUD

-----Message d'origine-----
De : Marcel Loose [mailto:loose at astron.nl] 
Envoyé : mardi 15 septembre 2009 09:38
À : Pierre-Julien Villoud
Cc : cmake at cmake.org
Objet : RE: [CMake] add_subdirectory and build directory

Hi Pierre-Julien,

You are right. You don't need add_dependencies() when specifying link
dependencies using target_link_libraries(). The latter, BTW, is of
course the preferred way to do this.

Without an example of you CMakeLists.txt files, it's very hard to tell
what, if anything, is going wrong.

Regards,
Marcel Loose.

On Mon, 2009-09-14 at 16:28 +0200, Pierre-Julien Villoud wrote:
> 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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