In JSStack::enableErrorStackReserve() and disableErrorStackReserve(), m_useableEnd is initialize to reservationTop() or reservationTop() + commitSize. Hence, it points to an allocatable slot in the stack, not past it. Naming it m_useableTop is more correct. Will rename.
Created attachment 219935 [details] the patch.
Landed in r161027 on the jsCStack branch: <http://trac.webkit.org/r161027>.
Comment on attachment 219935 [details] the patch. r=me
Thanks. Review status updated in r161934 on the jsCStack branch: <http://trac.webkit.org/r161934>.