The sum of the length of substrings could overflow.
Created attachment 48759 [details] The patch No perf impact.
Comment on attachment 48759 [details] The patch r=me
Sending JavaScriptCore/ChangeLog Sending JavaScriptCore/runtime/UString.h Transmitting file data .. Committed revision 54788.
Errk! - thanks darin/aroben, made the output bool a reference in r54795. Darin - I will separately check the performance of using |=. My instinct is often to go with the branch, since on x86 the setcc instruction used to be multiple cycle, and a well predicted branch can be free. In this case there may be little performance difference, since I don't think makeString is heavily used or performance critical. As such perhaps I should switch to |=, since it's a line shorter. :o)