How to add_dependencies between projects in cmake

Question

include_directories(${CMAKE_CURRENT_SOURCE_DIR})
AUX_SOURCE_DIRECTORY(${CMAKE_CURRENT_SOURCE_DIR} source)

project(abc)
#a_certain_source_file.cpp is a generated file built by another project.
add_library(${PROJECT_NAME} STATIC ${source} ${xyz_BIN_DIR}/a_certain_source_file.cpp)
add_dependencies(${PROJECT_NAME} xyz)


target_link_libraries(${PROJECT_NAME} PRIVATE xyz)
# include xyz_SOURCE_DIR directory to include a_certain_source_file.cpp
target_include_directories(${PROJECT_NAME} PRIVATE ${xyz_SOURCE_DIR})


# Installation
install(TARGETS ${PROJECT_NAME} DESTINATION ${DST_LIB_DIR})

I have a CMakeLists.txt as above. Trying to build project abc. But to build it, I also need "a_certain_source_file.cpp" which is an auto generated source file from another project called xyz. If xyz had been built from this same CMakeLists.txt, there would have been no problem in add_dependencies working. I am unable to get the dependency on "a_certain_source_file.cpp" resolved with the way i have my CMakeLists.txt right now. Any CMake Enthusiasts or specialists that can help ?

I also saw a close match here - cmake: add_dependencies does not work with external projects but I don't need anything downloaded. So am not sure if this is what I need.

Answer 1

Create custom command with add_custom_command marking ${xyz_BIN_DIR}/a_certain_source_file.cpp as OUTPUT and make it depend on a xyz target. This will teach CMake that ${xyz_BIN_DIR}/a_certain_source_file.cpp is a generated file, and what should it do to generate it.