gc.c: Enable DEBUG(x) if GC_DEBUG is defined.

vm.c: Enable DEBUG(x) if VM_DEBUG is defined.

src/gc.c

@@ -147,8 +147,10 @@ gettimeofday_time(void)
 #ifdef GC_DEBUG
 #include <assert.h>
 #define gc_assert(expect) assert(expect)
+#define DEBUG(x) (x)
 #else
 #define gc_assert(expect) ((void)0)
+#define DEBUG(x)
 #endif
 
 #define GC_STEP_SIZE 1024

src/vm.c

@@ -49,7 +49,11 @@ The value below allows about 60000 recursive calls in the simplest case. */
 #define MRB_STACK_MAX ((1<<18) - MRB_STACK_GROWTH)
 #endif
 
-
+#ifdef VM_DEBUG
+# define DEBUG(x) (x)
+#else
+# define DEBUG(x)
+#endif
 
 static inline void
 stack_copy(mrb_value *dst, const mrb_value *src, size_t size)