CMake: How to add dependency on linker script for

Question

I have a CMake script where the final executable is linked with my own linker script:

cmake_minimum_required(VERSION 3.1)

project(test_app)

set(LINKER_SCRIPT "linker.ld")
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -T ${LINKER_SCRIPT}")

add_executable(${PROJECT_NAME}.elf
    main.cpp
    startup.cpp
)

How do I make an executable dependent also on the linker script file (trigger linking if linker.ld was changed)?

Answer 1

You can add a LINK_DEPENDS property to your executable target, using set_target_properties. Add the following line after your add_executable command:

set_target_properties(${TARGET_NAME} PROPERTIES LINK_DEPENDS ${LINKER_SCRIPT})

The first argument to set_target_properties is the target name, i.e. the first argument you passed to add_executable.

Answer 2

I found this mail which described three possible ways for forcing an executable to be dependent on a linker script. Its author prefers this way:

CMakeLists.txt:

CMAKE_MINIMUM_REQUIRED(VERSION 2.8 FATAL_ERROR)
PROJECT(LINKERSCRIPT C)
FILE(WRITE main.c "void main(){}")
# dummy.c must exist:
ADD_EXECUTABLE(EXE main.c dummy.c)
# linkerscript must exist:
SET_SOURCE_FILES_PROPERTIES(
    dummy.c PROPERTIES OBJECT_DEPENDS ${CMAKE_SOURCE_DIR}/linkerscript
)

Here dummy.c is an empty file, which is listed for the add_executable() command only for make resulted executable dependent on the linker script via the OBJECT_DEPENDS property.