[CMake] Why are object files built several times?

[Andreas Pakulat]

On 26.09.07 15:13:38, Dizzy wrote:
> On Wednesday 26 September 2007 14:55:52 Joachim Ziegler wrote:
> > Hello,
> >
> > I have two targets that have nearly the same sources:
> >
> > ADD_EXECUTABLE(startCompletionServer StartCompletionServer.cpp
> > ${BASEFILES}) ADD_EXECUTABLE(test-adler32 test-adler32.cpp ${BASEFILES})
> >
> > I wonder why every object file belonging to the BASEFILES is built
> > twice, once for the first target, once again for the second. This
> > doubles my compile time!?
> 
> You will notice that cmake is building files inside a build directory 
> different for each target. So it is ment to be that way (normally you may 
> have different compile flags for different targets so you want that). If you 
> do not want that then just put your BASEFILES in a "convenience library" and 
> reuse it from both targets such as:

Note that this creates a static convenience library which is not
portable to some architectures without extra compiler flags (need -fPIC
on amd64 and maybe other 64bit architectures).

Another way is to create a shared lib (and also install that one), but
don't provide headers for the library and don't give it a SOVERSION so
people won't link against it.

Andreas

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