CMAKE_<LANG>_IMPLICIT_INCLUDE_DIRECTORIES

Directories implicitly searched by the compiler for header files.

CMake does not explicitly specify these directories on compiler command lines for language <LANG>. This prevents system include directories from being treated as user include directories on some compilers, which is important for C, CXX, and CUDA to avoid overriding standard library headers.

This value is not used for Fortran because it has no standard library headers and some compilers do not search their implicit include directories for module .mod files.