How to handle gcc link options(like whole-archive,

Question

I have a demo project and it's structure like as below:

top_dir 
    CMakeLists.txt 
    sub_dir1 
        CMakeLists.txt 
    sub_dir2 
        CMakeLists.txt 

top_dir/sub_dir1/CMakeLists.txt used to build lib1 by using add_library(lib1 ...), top_dir/sub_dir2/CMakeLists.txt used to build exe1 with linking lib1 by target_link_library(exe1 lib1).

And the content of top_dir/CMakeLists.txt is as below:

add_subdirectory(sub_dir2) 
add_subdirectory(sub_dir1) 

Normally, when build target exe1, cmake will check dependency so lib1 will be built before building exe1. The problem is I am transfering an existed makefile project into CMake, and there are many gcc link options, like "whole-archive ... no-whole-archive, allow-mutiple-definition", if use like target_link_library(exe1 "-Wl, --whole-archive ../sub_dir1/liblib1.a --no-whole-archive")(The form like this, and this may not work, it just a e.g.), cmake seem don't built lib1 any more. Is there any way i can use target_link_library like target_link_library(exe1 "-Wl, --whole-archive ../sub_dir1/liblib1.a") and cmake link dependency checking still work, or other way i can transfer these gcc link options into cmake?

Answer 1

The next hack permits to locally define the flags to the library to which you want to apply the flags, without modifying all exe link flags :

add_library(lib1_internal STATIC lib1.cpp)
add_library(lib1 STATIC dummy.cpp) # dummy.cpp is an empty file

target_link_libraries(lib1  PRIVATE -Wl,--whole-archive lib1_internal -Wl,--no-whole-archive )  

....

target_link_libraries(exe1 lib1)

Answer 2

Arguments for target_link_libraries are going into the resulted command line in the same order they appears. Whenever target name is used as argument, path to target's output is used in resulted command line. So, you may use library target whenever you need path to that library in the command line:

target_link_libraries(exe1 -Wl,--whole-archive lib1 -Wl,--no-whole-archive)

Such a way a target-level dependency between executable exe1 and library lib1 is automatically deduced by CMake, as usual.