Multiple source directories for one executable with CMake

Question

I want my source organised in a number of subdirectories but be able to create a single executable without having to build a library for each subdirectory. Can CMake do this

Answer 1

Another (arguably better for big code bases) variant is to use a separate CMakeLists.txt for each sub-directory where you isolate adding sources of the directory to a target using target_sources and maybe some particular configuration settings \ include conditions for those sources:

target_sources( SomeExeOrLib PRIVATE source1.h source1.cpp )

here you also have more control of the scope by specifying PRIVATE, other options are INTERFACE or PUBLIC. See details here: https://cmake.org/cmake/help/v3.3/command/target_sources.html

Answer 2

Here the my simple example

cmake_minimum_required(VERSION 2.8 FATAL_ERROR)
project(foo CXX)
# get all *.cpp files recursively
file(GLOB_RECURSE SRC_FILES ${PROJECT_SOURCE_DIR}/*.cpp)
add_executable(foo ${SRC_FILES})

Answer 3

Yes, that would work.

Update: What follows is not very relevant anymore because nowadays CMake supports response files, so there shouldn't be problems with too long command lines.

However you might have troubles when the number of files get too high, and the command line too long for your compiler to be able to handle it. A possible solution is to add a static library for each subdirectory, add them to a list "ALL_MY_SUB_LIBS", and link them to the main target foo in this way:

target_link_libraries(foo "-Wl,--whole-archive") #like opening a parenthesis
target_link_libraries(foo ${ALL_MY_SUB_LIBS}) 
target_link_libraries(foo "-Wl,--no-whole-archive") #like closing a parenthesis

ld linker question: the --whole-archive option