how do i build libraries in subdirectories using cmake? - c++

Question

My code is organized like this:
cpp
main.cpp (calls code from dataStructures/ and common/)
CMakeLists.txt (topmost CMakeLists file)
build
common
CMakeLists.txt (should be responsible for building common shared library)
include
utils.h
src
utils.cpp
build
dataStructures
CMakeLists.txt (build dataStructures shared library - dependent on common library)
include
dsLinkedList.h
src
dsLinkedList.cpp
build
build\ directories contain the built target. The actual code can be seen here: https://github.com/brainydexter/PublicCode/tree/master/cpp
As of now, CMakeLists.txt in each of the subdirectories build their own shared libraries. Topmost CMakeLists file then references the libraries and paths like this
Topmost CMakeLists.txt
cmake_minimum_required(VERSION 3.2.2)
project(cpp)
#For the shared library:
set ( PROJECT_LINK_LIBS libcppDS.dylib libcppCommon.dylib)
link_directories( dataStructures/build )
link_directories( common/build )
#Bring the headers, into the project
include_directories(common/include)
include_directories(dataStructures/include)
#Can manually add the sources using the set command as follows:
set(MAINEXEC main.cpp)
add_executable(testDS ${MAINEXEC})
target_link_libraries(testDS ${PROJECT_LINK_LIBS} )
How can I change the topmost CMakeLists.txt to go into subdirectories (common and dataStructures) and build their targets if they haven't been built, without me having to manually build the individual libraries ?
CMakeLists for common :
cmake_minimum_required(VERSION 3.2.2)
project(cpp_common)
set(CMAKE_BUILD_TYPE Release)
#Bring the headers, such as Student.h into the project
include_directories(include)
#However, the file(GLOB...) allows for wildcard additions:
file(GLOB SOURCES "src/*.cpp")
#Generate the shared library from the sources
add_library(cppCommon SHARED ${SOURCES})
dataStructures :
cmake_minimum_required(VERSION 3.2.2)
project(cpp_dataStructures)
set(CMAKE_BUILD_TYPE Release)
#For the shared library:
set ( PROJECT_LINK_LIBS libcppCommon.dylib )
link_directories( ../common/build )
#Bring the headers, such as Student.h into the project
include_directories(include)
include_directories(../common/include/)
#However, the file(GLOB...) allows for wildcard additions:
file(GLOB SOURCES "src/*.cpp")
#Generate the shared library from the sources
add_library(cppDS SHARED ${SOURCES})
Update:
This pull request helped me understand the correct way of doing this:
https://github.com/brainydexter/PublicCode/pull/1
and commitId: 4b4f1d3d24b5d82f78da3cbffe423754d8c39ec0 on my git

Answer 1

You are only missing a simple thing: add_subdirectory.
From the documentation:
add_subdirectory(source_dir [binary_dir] [EXCLUDE_FROM_ALL])
Add a subdirectory to the build. The source_dir specifies the directory in which the source CMakeLists.txt and code files are located. If it is a relative path it will be evaluated with respect to the current directory (the typical usage), but it may also be an absolute path. The binary_dir specifies the directory in which to place the output files. If it is a relative path it will be evaluated with respect to the current output directory, but it may also be an absolute path.
http://www.cmake.org/cmake/help/v3.0/command/add_subdirectory.html
It does exactly what you need.