error.c: negative uplevel

* error.c (rb_warn_m): negative uplevel is not allowed.
  [ruby-core:84568] [Bug #14262]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61525 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

error.c

@@ -342,7 +342,11 @@ rb_warn_m(int argc, VALUE *argv, VALUE exc)
 		uplevel = Qnil;
 	    }
 	    else if (!NIL_P(uplevel)) {
-		uplevel = LONG2NUM((long)NUM2ULONG(uplevel) + 1);
+		long lev = NUM2LONG(uplevel);
+		if (lev < 0) {
+		    rb_raise(rb_eArgError, "negative level (%ld)", lev);
+		}
+		uplevel = LONG2NUM(lev + 1);
 		uplevel = rb_vm_thread_backtrace_locations(1, &uplevel, GET_THREAD()->self);
 		if (!NIL_P(uplevel)) {
 		    uplevel = rb_ary_entry(uplevel, 0);

test/ruby/test_exception.rb

@@ -1007,6 +1007,7 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
   def test_kernel_warn_uplevel
     warning = capture_warning_warn {warn("test warning", uplevel: 0)}
     assert_equal("#{__FILE__}:#{__LINE__-1}: warning: test warning\n", warning[0])
+    assert_raise(ArgumentError) {warn("test warning", uplevel: -1)}
   end
 
   def test_warning_warn_invalid_argument