llvm/clang/test/Modules/Inputs/macro-ambiguity/c/system/c_system.h

#ifndef C_SYSTEM_H
#define C_SYSTEM_H

// FIXME: We have to use this to mark the header as a system header in
// a module because header search didn't actually occur and so we can't have
// found the header via system header search, even though when we map to this
// header and load the module we will have mapped to the header by finding it
// via system header search.
#pragma GCC system_header

#define FOO1_SYSTEM(x) 2 * x
#define FOO2_SYSTEM(x) 2 * x

#endif