Adding multiple executables in CMake - c++

Question

My code in a C++ project is organised as follows
I have several .cpp and .h files which contains my classes
I have several .cxx files which have to be compiled against the .cpp files and some external libraries.
Now, each of the .cxx files have a main() method, so I need to add a different executable for each of these files having the same name as the file.
Also, these .cxx files might not get linked to the same external libraries.
I want to write this build in CMake, in which I am kind of a newbie, how do I go about this?

Answer 1

My suggestion is to tackle this in two phases:
Build a library from the .cpp and .h files, using add_library
Iterate through all your .cxx files and create an executable from each, using add_executable and foreach
Build the library
This could be something as simple as
file( GLOB LIB_SOURCES lib/*.cpp )
file( GLOB LIB_HEADERS lib/*.h )
add_library( YourLib ${LIB_SOURCES} ${LIB_HEADERS} )
Build all the executables
Simply loop over all the .cpp files and create separate executables.
# If necessary, use the RELATIVE flag, otherwise each source file may be listed
# with full pathname. RELATIVE may makes it easier to extract an executable name
# automatically.
# file( GLOB APP_SOURCES RELATIVE app/*.cxx )
file( GLOB APP_SOURCES app/*.cxx )
foreach( testsourcefile ${APP_SOURCES} )
# I used a simple string replace, to cut off .cpp.
string( REPLACE ".cpp" "" testname ${testsourcefile} )
add_executable( ${testname} ${testsourcefile} )
# Make sure YourLib is linked to each app
target_link_libraries( ${testname} YourLib )
endforeach( testsourcefile ${APP_SOURCES} )
Some warnings:
file( GLOB ) is usually not recommended, because CMake will not automatically rebuild if a new file is added. I used it here, because I do not know your sourcefiles.
In some situations, source-files may be found with a full pathname. If necessary, use the RELATIVE flag for file(GLOB ...).
Manually setting the source-files requires a change to CMakeLists.txt, which triggers a rebuild. See this question for the (dis-)advantages of globbing.
I generated the testname using a string( REPLACE ... ). I could have used get_filename_component with the NAME_WE flag.
Concerning "general" CMake info, I advise you to read some of the broad "CMake Overview" questions already asked here on stackoverflow. E.g.:
https://stackoverflow.com/questions/2186110/cmake-tutorial
What are the dusty corners a newcomer to CMake will want to know?

Answer 2

I find myself in a similar situation when organizing an OpenGL project with multiple sample files where each of these files contain a main method.
The settings below will generate a separate executable per c/cpp file as well as copying required dependencies to the target bin folder.
Folder Structure
my-project
│── ch01_01.c
│── ch02_01.cpp
│── CMakeLists.txt
│── Resources
│ │── Libraries
│ │ │── glew
│ │ │ │── bin
│ │ │ │── include
│ │ │ │── lib
│ │ │── glfw
│ │ │ │── include
│ │ │ │── lib
CMakeLists.txt
cmake_minimum_required (VERSION 3.9)
project ("my-project")
include_directories(Resources/Libraries/glew/include
Resources/Libraries/glfw/include)
link_directories(Resources/Libraries/glew/lib
Resources/Libraries/glfw/lib)
link_libraries(opengl32.lib
glew32.lib
glfw3.lib)
set(CMAKE_EXE_LINKER_FLAGS "/NODEFAULTLIB:MSVCRT")
file(GLOB SOURCE_FILES *.c *.cpp)
foreach(SOURCE_PATH ${SOURCE_FILES})
get_filename_component(EXECUTABLE_NAME ${SOURCE_PATH} NAME_WE)
add_executable(${EXECUTABLE_NAME} ${SOURCE_PATH})
# Copy required DLLs to the target folder
add_custom_command(TARGET ${EXECUTABLE_NAME} POST_BUILD
COMMAND ${CMAKE_COMMAND} -E copy_if_different "${CMAKE_SOURCE_DIR}/Resources/Libraries/glew/bin/glew32.dll"
"${CMAKE_BINARY_DIR}/glew32.dll")
endforeach(SOURCE_PATH ${SOURCE_FILES})
Optional Steps
In Visual Studio
Open the project with 'Open a local Folder' option in the Start Window
When adding a new file you may either:
Cancel the dialog asking to automatically add_executable to CMakeLists.txt
Disable this behavior by unchecking 'Enable automatic CMake script modification for file operations from folder view' in Tools > Options > CMake
As newly added files are not picked up automatically as CMakeLists.txt is never changed, simply regenerate the cache like so:
Project > CMake Cache (x64-Debug) > Delete Cache
Project > Generate Cache for my-project
Now you may simply right click a given c/cpp file and Set as Startup Item to be able to debug it with F5.
Environment
cmake version 3.18.20081302-MSVC_2
Microsoft Visual Studio Community 2019 Version 16.8.3
Starter Template
I put together this starter template on GitHub in case you are interested.

Answer 3

This CMakeLists.txt works for my OpenCV project
assuming *.cpp files are in the same directory as CMakeLists.txt
cmake_minimum_required(VERSION 3.5)
project(opencv LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
find_package(OpenCV REQUIRED)
include_directories( ${OpenCV_INCLUDE_DIRS} )
file( GLOB APP_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/*.cpp )
foreach( sourcefile ${APP_SOURCES} )
file(RELATIVE_PATH filename ${CMAKE_CURRENT_SOURCE_DIR} ${sourcefile})
string( REPLACE ".cpp" "" file ${filename} )
add_executable( ${file} ${sourcefile} )
target_link_libraries( ${file} ${OpenCV_LIBS} )
endforeach( sourcefile ${APP_SOURCES} )