The CMake System

The CMake system consists of a CMakeLists.txt file that describes how to generate the make file that will be used for building a project. The initial CMakeLists.txt file consisted of these major sections:

1. Check that the GCC version is 4.5 or later.
2. Find the awk program.
3. Pass version information to the IBCP source.
4. Create custom commands for the auto-generated header files.
5. Define the lists of header and source files.
6. Add linker definitions for the static library linking.
7. Define the executable.

Step 1 is needed to make sure the needed version of the GCC compiler is installed and setup correctly. Step 2 checks if the awk program is available and gets it's path - the awk program is needed to create the auto-generated header files. Step 3 is to pass program version and copyright information to the source program. This is accomplished by an ibcp_config.h.in file with definitions set to CMake variables to create an ibcp_config.h file that will be included in the source.

Step 4 contains two custom commands to run awk to create the two auto-generated header files. The awk scripts were modified to take a command line argument for the path of where the output files are to written to since the awk scripts will be run in the build directory, not in the source directory. This path argument was made optional and if not provided, the awk scripts assume the current directory. In the CMakeLists.txt custom commands, the source directory path is passed to the awk scripts. The auto-generated header files are now written into the build directory (CMake calls this the binary directory), not the source directory, so a statement was also needed in CMakeLists.txt to include the binary directory to the list of paths that are searched for header files.

In Step 5, the list of header and source files are put into CMake variables. These variables are used to define what the dependencies are and are used to build the executable. Step 6 adds the ‑static‑libgcc and ‑static‑libstc++ linker options. Finally, Step 7 defines the executable, which depends on the auto-generated header files, the project header files and the source files. The ".exe" is not needed on the executable program name as CMake will automatically add it for Windows, but not for Linux (CMake is aware of which system is being used for building).