Bug 34462 – Fix a bug that Math.round() returns incorrect results for huge integers

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Kent Tamura]

Fix a bug that Math.round() retunrs incorrect results for huge integers

[Kent Tamura]

Created attachment 47901 [details]
Patch

[Darin Adler]

Comment on attachment 47901 [details]
Patch

How about this instead?

-    if (signbit(arg) && arg >= -0.5)
-         return jsNumber(exec, -0.0);
-    return jsNumber(exec, floor(arg + 0.5));
+    double integer = ceil(arg);
+    return jsNumber(exec, integer - (integer - arg > 0.5));

[Darin Adler]

Comment on attachment 47901 [details]
Patch

Patch seems fine. But you should consider my patch with ceil that avoids the need for the separate if statement. You could use ? : instead of the way I did it. Or use my code exactly as is (as long as it passes your tests).

[Darin Adler]

Would be nice to have tests cases for the maximum and minimum double values as well to make sure they don't turn into infinity when rounded.

[Kent Tamura]

Thank you for the quick review.

Ok, I followed the proposed code, and add test cases for minimum/maximum values.

Landed as r54197 and r54198.