cmake - Postpone making custom target until install

Question

I have something like this in my project:

add_custom_command(OUTPUT somefile)
add_custom_target(tgt ALL DEPENDS somefile)

install(FILES ${CMAKE_CURRENT_BINARY_DIR}/somefile DESTINATION somedir)

This works OK, but my command is being run during make because of ALL keyword in add_custom_target(). What i want is to make CMake to run this command only when make install is issued, not during build.

If i remove ALL keyword, whole target is not being built by default, so somefile is not produced and make install fails.

Answer 1

A possible solution is to have the make install command invoke the make tgt as a side effect. This can be done by using the CODE signature of the install command:

add_custom_command(OUTPUT somefile)
add_custom_target(tgt DEPENDS somefile)

install(CODE "execute_process(COMMAND "${CMAKE_COMMAND}" --build "${CMAKE_CURRENT_BINARY_DIR}" --target tgt)")
install(FILES ${CMAKE_CURRENT_BINARY_DIR}/somefile DESTINATION somedir)

The execute_process invokes cmake to build the target tgt before somefile is installed.