Opencv: OpenCV 3.1.0 build fails on Windows with Ninja Generator

[willyd]

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Please state the information for your system

• OpenCV version: 3.1.0
• Host OS: Windows 10

• Compiler & CMake: MSVC 120 & CMake 3.5

  In which part of the OpenCV library you got the issue?

• CMakeLists.txt

  Expected behaviour

Build succeeds

Actual behaviour

LINK : fatal error LNK1104: cannot open file 'Files\NVIDIA.obj'

Additional description

This line breaks the build with Ninja under Windows. I think the line should be:

# this
set(OPENCV_LINKER_LIBS ${OPENCV_LINKER_LIBS} ${CMAKE_LIBRARY_PATH_FLAG}$<SHELL_PATH:${p}>)
# instead of that
# set(OPENCV_LINKER_LIBS ${OPENCV_LINKER_LIBS} -L${p})

But even with this change the build fails because of the spaces in the path which Ninja does not like. Maybe $<SHELL_PATH:...> should return a short path but that's a CMake issue.

As a workaround one can use:

if(NOT CMAKE_GENERATOR MATCHES "Ninja" AND NOT MSVC)
  set(OPENCV_LINKER_LIBS ${OPENCV_LINKER_LIBS} -L${p})
endif()   

This problem also affects consuming projects as the link flags end up in the OpenCVModules*.cmake files.

I find Ninja much faster than msbuild on Windows especially when building with CUDA so it would be nice if OpenCV supported this generator too.

[willyd]

Posted a related issue to CMake bug tracker: https://cmake.org/Bug/view.php?id=16053

[mshabunin]

You can use /maxcpucount option with msbuild to speed up the build process. The example for 4-core CPU:

.cmd cmake --build . --config release -- /maxcpucount:5

[mloskot]

@mshabunin with respect, but the maxcpucount nothing to do really w.r.t. parallel compilation of translation units.