CMake SWIG dependency on headers of external project

Question

I have a project "A" that depends on another project "B".

• ProjectB installs some headers, for example B1.h, B2.h.
• ProjectA tries to create a Python wrapper of B1.h and B2.h, using SWIG.

ProjectA uses :

• ExternalProject_Add(ProjectB ...) to compile and install ProjectB somwhere into the binary dir.
• Swig_Add_Library(ProjectB ...) to create the Python wrapper ; this command creates a target _ProjectB.

I want to be sure that B1.h, B2.h are installed before SWIG runs, thus I added the following command : add_dependencies(_ProjectB ProjectA)

On Windows, this works fine.

However on Linux, the add_dependencies command is not taken into account, which gives :

.../ProjectA.i: 111: Error: Unable to find 'B1.h'
.../ProjectA.i: 112: Error: Unable to find 'B2.h'

I am sure that the include dir given to SWIG is correct: indeed, when I run make for the second time, this works because ProjectB was successfully installed by the first call to make.

I use CMake 3.13.5.

Any help would be great !

Answer 1

I found a workaround : on Linux, I use : add_dependencies(ProjectB_swig_compilation ProjectA)

However, the target ProjectB_swig_compilation does not exist on Windows (I don't understand why since I use the same version of CMake on both Linux and Windows).

Eventually, here is what I did in my CMakeLists.txt :

if (WIN32 AND NOT MINGW)
   add_dependencies(_ProjectB ProjectA)
else ()
   add_dependencies(ProjectB_swig_compilation ProjectA)
endif ()