CMake: How to add dependency on linker script for executable

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)?

Linker script is edited by hand, at this time if I make changes in this script, then I must re-build project. — vlk
– vlk, Commented Sep 30, 2015 at 12:29
I try to add this: add_custom_target(OUTPUT ${PROJECT_NAME}.elf DEPENDS ${LINKER_SCRIPT}) but without success. — vlk
– vlk, Commented Sep 30, 2015 at 12:44
See LINK_DEPENDS target property. This works for all makefile generators except - until now - for Ninja (will be fixed with CMake 3.4, see 0014796: LINK_DEPENDS should work with Ninja backend) — Florian
– Florian, Commented Oct 1, 2015 at 10:15
Florian, look like this is the right way and is working for me (I use Makefile), can you create an answer, I accept it. Thanks. — vlk
– vlk, Commented Oct 1, 2015 at 11:13

starball · Accepted Answer · 2022-09-17 23:08:36Z

34

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.

edited Sep 17, 2022 at 23:08

starball♦

59.8k53 gold badges318 silver badges1k bronze badges

answered Feb 9, 2017 at 13:44

Samuel Peter

4,2142 gold badges36 silver badges44 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

vlk Over a year ago

The problem is that cmake searching for ${LINKER_SCRIPT} in build directory instead of in source directory. Actually I have solution to add ${CMAKE_SOURCE_DIR}/${LINKER_SCRIPT}

Ryan Over a year ago

Or ${CMAKE_CURRENT_SOURCE_DIR}/${LINKER_SCRIPT} to search in the directory that the add_executable is defined in.

Peter Mortensen · Accepted Answer · 2019-01-12 20:28:15Z

0

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.

edited Jan 12, 2019 at 20:28

Peter Mortensen

31.4k22 gold badges110 silver badges134 bronze badges

answered Sep 30, 2015 at 17:07

Tsyvarev

67.7k18 gold badges142 silver badges189 bronze badges

2 Comments

vlk Over a year ago

Yes, I known about this solution with dummy.c file, but I don't think it is very elegant. For example if into Makefile I add empty target: outupt.elf: linker.ln beside linking target: output.elf: main.o startup.o then I get what I want, but I don't know how can I create an empty target with CMake, or if this is possible.

Tsyvarev Over a year ago

Yes, with direct using of Makefile, adding linker dependency is simpler and more elegant. But CMake doesn't allow adding dependencies for one file more than once. First time dependencies are added in add_executable() call, but all of them should be source or header files, so you cannot add linker-dependency at this stage. From the other side, you needn't to bother about Makefiles produced by CMake. They are much more complex than manually written files in any case.

Collectives™ on Stack Overflow

CMake: How to add dependency on linker script for executable

2 Answers 2

2 Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related