CMake - add_executable called with incorrect number of arguments

Question

I am trying to organize a C++ project which starts to have a lot of files. I would like to create two executables which share some source file using Cmake. I have found an interesting procedure here:

How to add source files in another folder

Below is my version of the thing

file(GLOB Common_sources RELATIVE "Common" "*cpp")
file(GLOB Mps_sources RELATIVE "Mps" "*.cpp")                 
file(GLOB Mss_sources RELATIVE "Mss" "*.cpp") 

add_executable(test_mss ${Common_sources} ${Mss_sources}) 
add_executable(test_mps ${Common_sources} ${Mps_sources})

But CMake complains

CMake Error at src/CMakeLists.txt:44 (add_executable):
add_executable called with incorrect number of arguments

CMake Error at src/CMakeLists.txt:45 (add_executable):
add_executable called with incorrect number of arguments

It says to look at CMakeOutput.log, but the file is really too long, I can not find useful information.

I checked the CMake documentation, it seems that it can take a second source as an additional argument. https://cmake.org/cmake/help/v3.0/command/add_executable.html

I would like to find the source of this bug. I have the feeling that I am missing something obvious here.

Answer 1

The error you get is because source list, passed to add_executable, is actually empty.

Correct way for collect sources in Common/ subdirectory is:

file(GLOB Common_sources "Common/*.cpp")

---

In command file(GLOB) RELATIVE option doesn't specify search directory. Instead, it just tells CMake to generate relative paths instead of absolute:

If RELATIVE flag is specified, the results will be returned as relative paths to the given path.

Assuming

file(GLOB Common_sources "Common/*.cpp")
# gets: /<path-to-source>/Common/my_source.cpp

then (also note to absolute path in RELATIVE option)

file(GLOB Common_sources RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}/Common" "Common/*.cpp")
# gets: my_source.cpp

and (when files are not under RELATIVE directory)

file(GLOB Common_sources RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}/Mps" "Common/*.cpp")
# gets: ../Common/my_source.cpp

Answer 2

You have to quote the variables.

add_executable(test_mss "${Common_sources}" "${Mss_sources}")

Otherwise for an empty variable, CMake replaces the variable by nothing and the number of arguments seems to be wrong.

Similar problem: https://stackoverflow.com/a/39733128/2799037