rt_gccstream/gcc/testsuite/gcc.dg/cpp/warn-unused-macros.c

// { dg-do preprocess }
// { dg-options "-std=gnu99 -fdiagnostics-show-option -Wunused-macros" }

#define X X  // { dg-warning "macro \"X\" is not used .-Wunused-macros." }