SET_WHEN          120 debug.c            SET_WHEN("gc_stress", *ruby_initial_gc_stress_ptr, Qtrue);
SET_WHEN          121 debug.c            SET_WHEN("core", ruby_enable_coredump, 1);
SET_WHEN          123 debug.c            SET_WHEN("rtc_error", ruby_w32_rtc_error, 1);
SET_WHEN          856 ruby.c         #define SET_WHEN_DEBUG(bit) SET_WHEN(#bit, DEBUG_BIT(bit), str, len)
SET_WHEN          866 ruby.c         #define SET_WHEN_DUMP(bit) SET_WHEN(#bit, DUMP_BIT(bit), str, len)