两个子项目 A 和 B，A 依赖于 B 并检查 B 中存在的功能

Question

I'm trying to create a CMake project that integrates 2 sub-projects, specifically botan and rnpgp . The build system of rnpgp is CMake-based, botan uses a Python configure script to generate a Makefile. The problem is that during the CMake run rnpgp checks for features in botan, so it requires a compiled botan library. But, botan doesn't get built until I actually call make , which I can't do because rnpgp fails to configure because botan isn't built yet.

What's the right way to specify such a dependency in CMake?

Answer 1

You could use CMake's execute_process() to run the botan Python script and run make during the CMake configure stage. This way, the botan library will be built and available to reference when running the mpgp CMake:

# Run the Python script to configure the botan Makefile.
execute_process(COMMAND
    python ${CMAKE_SOURCE_DIR}/botan/configure.py
    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
)
# Run 'make' from the botan directory where the 'Makefile' was created.
execute_process(COMMAND
    make
    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}/botan/build"
)

This is a rough example of what it could look like. You may have to modify the paths a bit to match where you have botan on your system, and where botan generates its build artifacts (ie location of the Makefile).