gcc - Use -isystem instead of -I with CMake

Question

Is there any way in CMake to force a path specified via include_directories (or perhaps through a different function) to use the -isystem flag instead of the -I flag when building with gcc?

See http://gcc.gnu.org/onlinedocs/gcc/Directory-Options.html#Directory-Options for details on -I and -isystem.

Answer 1

Yes you force a path to be a system include by using the optional SYSTEM flag

include_directories(SYSTEM path)

http://www.cmake.org/cmake/help/cmake-2-8-docs.html#command:include_directories

Starting with CMake 2.8.12 you can use the new target_include_directories to include system directory includes at the target level, while leveraging the new usage requirement features of cmake:

target_include_directories(foo SYSTEM PUBLIC path)

Now target foo will use path as a system include, and anything that links to foo will also use path as automatically as a system include. You can control the propagation of these usage requirements by changing the PUBLIC keyword to PRIVATE or INTERFACE.

http://cmake.org/cmake/help/v2.8.12/cmake.html#command:target_include_directories