654734 - TrampolineCompiler::generateForceReturn should emit a call to ScriptDebugEpilogue

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Jason Orendorff [:jorendorff]]

Attachment: v1 (landed in jsdbg2)

The comment says:

/*
 * This is shamelessly copied from emitReturn, but with several changes:
 * - There was always at least one inline call.
 * - We don't know if there is a call object, so we always check.
 * - We don't know where we came from, so we don't know frame depth or PC.
 * - There is no stub buffer.
 */

emitReturn emits a call to stubs::ScriptDebugEpilogue in debug mode.

The trampoline generated by generateForceReturn can only be called in debug mode, so it should unconditionally emit a call to ScriptDebugEpilogue.

This patch applies on top of
  http://hg.mozilla.org/users/jblandy_mozilla.com/jsdbg2
revision 37b0503c5603.

Please take a look. I have no reason to believe this patch is safe. In particular I'm casting to void* without knowing anything about the types and calling conventions. (Also, ScriptDebugEpilogue can execute arbitrary JS code, due to debugging hooks; but if emitReturn does it I think it's probably safe to do it here too.)

Comment 1

[David Anderson [:dvander] - inactive, e-mail if emergency]

Yeah, this is safe, the calling convention for fallible vm calls is fastcall (VMFrame &), the return value can be anything and there can be one additional parameter. The VMFrame is passed implicitly.

Comment 2

[Jason Orendorff [:jorendorff]]

http://hg.mozilla.org/mozilla-central/rev/5fd40e7a5faf