Include directories

Most C/C++ projects have headers in different directories than sources. Thus you need to specify include directories. Let's assume that we are at some subdirectory and wish to add its include subdirectory to some target's search path. To create a include directory object we do this:

incdir = include_directories('include')

The incdir variable now holds a reference to the include subdir. Now we pass that as an argument to a build target:

executable('someprog', 'someprog.c', include_directories : incdir)

Note that these two commands can be given in any subdirectories and it will still work. Meson will keep track of the locations and generate proper compiler flags to make it all work.

Another thing to note is that include_directories adds both the source directory and corresponding build directory to include path, so you don't have to care. If it turns out you don't want it after all, this can be disabled with the implicit_include_directories argument to the build function you use.