c++ - Adding multiple executables in CMake

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:

1. Build a library from the .cpp and .h files, using add_library
2. 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 find( 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.:

• CMake tutorial
• What are the dusty corners a newcomer to CMake will want to know?