mrb_str_len_to_inum(): fixed a bug with MRB_INT_MIN conversion; fix #3048

src/string.c

@@ -2170,7 +2170,7 @@ mrb_str_len_to_inum(mrb_state *mrb, const char *str, size_t len, int base, int b
     }
     n *= base;
     n += c;
-    if (n > MRB_INT_MAX) {
+    if (n > (int64_t)MRB_INT_MAX + (sign ? 0 : 1)) {
       mrb_raisef(mrb, E_ARGUMENT_ERROR, "string (%S) too big for integer",
                  mrb_str_new(mrb, str, pend-str));
     }