SET_MACHINE_STACK_END    6 gc.h           #define SET_MACHINE_STACK_END(p) __asm__ __volatile__ ("movq\t%%rsp, %0" : "=r" (*(p)))
SET_MACHINE_STACK_END    8 gc.h           #define SET_MACHINE_STACK_END(p) __asm__ __volatile__ ("movl\t%%esp, %0" : "=r" (*(p)))
SET_MACHINE_STACK_END   11 gc.h           #define SET_MACHINE_STACK_END(p) rb_gc_set_stack_end(p)