I'm restucturing the CMake based build of a cross platform (macOS/Windows, Linux should be added soon) C++ project that has a third party rust library as dependendcy. Until now the rust lib dependency was supplied as precompiled library but I want to make its compilation part of my CMake build.
I got it working on macOS using the CMake makefile exporter by referencing the compiled library as a static imported library target and setting up a custom target with the command to build the rust library through cargo like this
add_library (rustlib STATIC IMPORTED)
add_custom_target (rustlib_cargo
WORKING_DIRECTORY ${CMAKE_CURRENT_LIST_DIR}/Ext/rustlib/c-api
COMMAND cargo rustc --release -- --crate-type staticlib)
# Note: RUSTLIB_OUTPUT is set above refering to the absolute path of the produced platform specific library
set_target_properties (rustlib PROPERTIES IMPORTED_LOCATION ${RUSTLIB_OUTPUT})
add_dependencies (rustlib rustlib_cargo)
On macOS the cargo rustc command is invoked before the targets that link against my rustlib target are built and in case the rust library has been built previously this is detected by cargo and it just skips that compilation steph. But on Windows this fails with the built-in ninja exporter of Microsoft Visual Studio 2019 with an error like this:
ninja : error : '../../../Ext/rustlib/target/release/deps/rustlib.lib', needed by 'SomeTargetLinkingAgainstRustlib', missing and no known rule to make it
If I remove the line set_target_properties (rustlib PROPERTIES IMPORTED_LOCATION ${RUSTLIB_OUTPUT}) the build starts correctly, the rust build gets triggered, but as expected I end up with a linker error as the library to link against is not found. So is there any way to refer to a file that is not existent at configuration time but is guranteed to be created during compilation?