CMake subdirectories dependency

Question

I am very new to CMake. In fact, I am trying it through Kdevelop4 widh C++.

I have the habit of creating subdirs for every namespace I create, even if all the sources must be compiled and linked into a single executable. Well, when i create a directory under kdevelop, it updates CMakeLists.txt with a add_subdirectory command and creates a new CMakeLists.txt under it, but that alone does not add the sources under it to the compilation list.

I have the root CMakeLists.txt as follows:

project(gear2d)

add_executable(gear2d object.cc main.cc)

add_subdirectory(component)

Under component/ I have the sources I want to be compiled and linked to produce the gear2d executables. How can I accomplish that?

CMake FAQ have this entry but if thats the answer I'd rather stay with plain Makefiles.

Is there a way of doing this?

Answer 1

Adding a subdirectory does not do much more than specify to CMake that it should enter the directory and look for another CMakeLists.txt there. You still need to create a library with the source files with add_library and link it to your executable with target_link_libraries. Something like the following:

In the subdir CMakeLists.txt

set( component_SOURCES ... ) # Add the source-files for the component here
# Optionally you can use file glob (uncomment the next line)
# file( GLOB component_SOURCES *.cpp )below

add_library( component ${component_SOURCES} )

Top-dir CMakeLists.txt

project( gear2d )
add_subdirectory( component )
add_executable( gear2d object.cc main.cc )
target_link_libraries( gear2d component )