Use sizeof to get char array sizes.

src/class.c

@@ -1149,11 +1149,11 @@ mrb_mod_to_s(mrb_state *mrb, mrb_value klass)
 
       switch (mrb_type(klass)) {
         case MRB_TT_CLASS:
-          snprintf(buf, 256, "#<Class:%p>", c);
+          snprintf(buf, sizeof(buf), "#<Class:%p>", c);
           break;
 
         case MRB_TT_MODULE:
-          snprintf(buf, 256, "#<Module:%p>", c);
+          snprintf(buf, sizeof(buf), "#<Module:%p>", c);
           break;
 
         default:

src/codegen.c

@@ -1537,7 +1537,7 @@ codegen(codegen_scope *s, node *tree, int val)
       int len;
       int sym;
 
-      len = snprintf(buf, 3, "$%c", (int)(intptr_t)tree);
+      len = snprintf(buf, sizeof(buf), "$%c", (int)(intptr_t)tree);
       sym = new_sym(s, mrb_intern2(s->mrb, buf, len));
       genop(s, MKOP_ABx(OP_GETGLOBAL, cursp(), sym));
       push();
@@ -1550,7 +1550,7 @@ codegen(codegen_scope *s, node *tree, int val)
       int len;
       int sym;
 
-      len = snprintf(buf, 3, "$%d", (int)(intptr_t)tree);
+      len = snprintf(buf, sizeof(buf), "$%d", (int)(intptr_t)tree);
       sym = new_sym(s, mrb_intern2(s->mrb, buf, len));
       genop(s, MKOP_ABx(OP_GETGLOBAL, cursp(), sym));
       push();

src/error.c

@@ -180,7 +180,7 @@ mrb_raise(mrb_state *mrb, struct RClass *c, const char *fmt, ...)
   int n;
 
   va_start(args, fmt);
-  n = vsnprintf(buf, 256, fmt, args);
+  n = vsnprintf(buf, sizeof(buf), fmt, args);
   va_end(args);
   if (n < 0) {
     n = 0;
@@ -197,7 +197,7 @@ mrb_name_error(mrb_state *mrb, mrb_sym id, const char *fmt, ...)
   int n;
 
   va_start(args, fmt);
-  n = vsnprintf(buf, 256, fmt, args);
+  n = vsnprintf(buf, sizeof(buf), fmt, args);
   va_end(args);
   if (n < 0) {
     n = 0;
@@ -216,7 +216,7 @@ mrb_sprintf(mrb_state *mrb, const char *fmt, ...)
   int n;
 
   va_start(args, fmt);
-  n = vsnprintf(buf, 256, fmt, args);
+  n = vsnprintf(buf, sizeof(buf), fmt, args);
   va_end(args);
   if (n < 0) {
     n = 0;

src/time.c

@@ -435,7 +435,7 @@ mrb_time_asctime(mrb_state *mrb, mrb_value self)
   tm = mrb_get_datatype(mrb, self, &mrb_time_type);
   if (!tm) return mrb_nil_value();
   d = &tm->datetime;
-  len = snprintf(buf, 256, "%s %s %02d %02d:%02d:%02d %s%d",
+  len = snprintf(buf, sizeof(buf), "%s %s %02d %02d:%02d:%02d %s%d",
 		 wday_names[d->tm_wday], mon_names[d->tm_mon], d->tm_mday, 
 		 d->tm_hour, d->tm_min, d->tm_sec,
 		 tm->timezone == MRB_TIMEZONE_UTC ? "UTC " : "",

src/vm.c

@@ -295,7 +295,7 @@ localjump_error(mrb_state *mrb, const char *kind)
   int len;
   mrb_value exc;
 
-  len = snprintf(buf, 256, "unexpected %s", kind);
+  len = snprintf(buf, sizeof(buf), "unexpected %s", kind);
   exc = mrb_exc_new(mrb, E_LOCALJUMP_ERROR, buf, len);
   mrb->exc = (struct RObject*)mrb_object(exc);
 }
@@ -308,12 +308,12 @@ argnum_error(mrb_state *mrb, int num)
   mrb_value exc;
 
   if (mrb->ci->mid) {
-    len = snprintf(buf, 256, "'%s': wrong number of arguments (%d for %d)",
+    len = snprintf(buf, sizeof(buf), "'%s': wrong number of arguments (%d for %d)",
 		   mrb_sym2name(mrb, mrb->ci->mid),
 		   mrb->ci->argc, num);
   }
   else {
-    len = snprintf(buf, 256, "wrong number of arguments (%d for %d)",
+    len = snprintf(buf, sizeof(buf), "wrong number of arguments (%d for %d)",
 		   mrb->ci->argc, num);
   }
   exc = mrb_exc_new(mrb, E_ARGUMENT_ERROR, buf, len);