[Webkit-unassigned] [Bug 173625] Web Inspector: Should be able to pause and debug a StackOverflow Exception

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Wed Jun 21 22:27:38 PDT 2017


--- Comment #3 from Mark Lam <mark.lam at apple.com> ---
FYI, you should take a look at JSC's Options::softReservedZoneSize() and Options::reservedZoneSize().

Under normal circumstances, JS stack usage is bounded by stack size - reserved zone size.  Stack size is determined by the lower of Options::maxPerThreadStackUsage() or system stack size.  The reserved zone size (or commonly known in OS parlance as the stack red zone size) is normally set to Options::softReservedZoneSize().  However, when handling an exception (e.g. when creating Error objects), the VM reduces the reserved zone size to Options::reservedZoneSize().  This gives the error code a little more room to play in.  The default difference between Options::softReservedZoneSize() and Options::reservedZoneSize() is 64K.

In order to not overflow the stack again while handling a StackOverflow, the Inspector code needs to play within this 64K range.  Note, not all of the 64K is available to the inspector.  The VM and native host code also uses some stack space.

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