[cmake-developers] CMAKE_CURRENT_SOURCE_DIR points to build dir at build time

[Paul Cercueil]

Hi,

I'm facing a strange issue with CMake 3.2.2 when building with Visual 
Studio.

This code snippet shows the problem:

--
set(CS_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/MyLib.cs
                ${CMAKE_CURRENT_SOURCE_DIR}/AssemblyInfo.cs)
add_custom_command(OUTPUT mylib.dll
                COMMAND mcs /target:library /out:mylib.dll /debug 
/keyfile:${CMAKE_CURRENT_SOURCE_DIR}/key.snk ${CS_SOURCES})
--

This will generate and build fine under Linux, using both Makefile or 
Ninja generators.

Under Windows, it will generate fine but Visual Studio will fail to 
build, stating that the "C:\build\Mylib.cs" and 
"C:\build\AssemblyInfo.cs" files cannot be found (source dir is 
"C:\src"). This indicates that it is in fact trying to find those files 
in the build directory, instead of the source directory.

This seems to happen only at the building step; at the generation step, 
${CMAKE_CURRENT_SOURCE_DIR} correctly points to "C:\src".

For a real-world example, this issue happens when compiling the libiio 
library with the C# bindings: http://github.com/analogdevicesinc/libiio.git

My current workaround is to copy the source files to the build directory:
https://gist.github.com/pcercuei/380550a3205c91f15b82

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