cmake project build only one specific executable (and its dependencies)

Question

I have a CMake Project with roughly this structure:

.
|-- library1
|   |-- CMakeLists.txt
|-- library2
|   |-- CMakeLists.txt
|-- executables
|   |-- CMakeLists.txt

I generate two executables in the folder named executables. I wonder if it was possible just generating one executable and its dependencies instead of all. I heard something about the cmake --target option but I cant get it to work with cmake/3.13.4.

Answer 1

There are a couple potential issues here. First, the typical CMake workflow places the build folder as a sibling to the top-level CMake file. So your file hierarchy should look something like this:

.
|-- CMakeLists.txt
|-- library1
|   |-- CMakeLists.txt
|-- library2
|   |-- CMakeLists.txt
|-- executables
|   |-- CMakeLists.txt
|-- build    <------------ Run CMake commands from here.

This isolates all the CMake-generated files to the build folder. Secondly, you must to careful to run the CMake build stages in the proper location. We can run everything from within the build folder, for example:

1. To generate the build system, run cmake .. from the build directory. This first step should point to the top-level CMake file.

2. To build (or compile) a specific target, say it's called MyExecutable1, run this:

   cmake --build . --target MyExecutable1
   

   from the build directory. You must be sure to point the --build flag at the build folder, not the top-level CMake file this time. Also, the target name to specify in this command should match the target name used in add_executable(), not the project name or anything else.

3. As always, when getting errors/issues while attempting to run CMake, it helps to clear the cache (delete build/CMakeCache.txt), or just delete the build folder altogether and start fresh.