On 2013/12/11 12:16:03, rossberg wrote:
On 2013/12/11 11:56:29, titzer wrote:
> On 2013/12/11 11:50:32, rossberg wrote:
> > https://codereview.chromium.org/110913004/diff/1/src/typing.cc
> > File src/typing.cc (left):
> >
> >
https://codereview.chromium.org/110913004/diff/1/src/typing.cc#oldcode53
> > src/typing.cc:53: if (visitor->HasStackOverflow()) return; \
> > Hm, is this really correct? It means that you do not bail out right
away
after
> > detecting a stack overflow, but instead each iteration will continue
trucking
> > along until it either returns or performs the next attempt to do a
recursive
> > call.
> >
> > If you view stack overflow as an exception-like condition, that isn't
quite
> the
> > right behaviour, and it seems fishy. In particular, consecutive code
could
> > happily try to call other auxiliary functions (with no stack check),
although
> > the stack space is already used up.
>
> Maybe we should check before and after then. I saw a crasher that
failed the
> ASSERT that was there previously. I think it makes sense to do a check
before,
> otherwise one could recurse down the first child all the way without
noticing
> the overflow yet.
Hm, if there can be early stack overflow conditions without the function
having
bailed out already then the same bad scenario could happen _before_ the
first
recursive call.
What bad scenarios are you envisioning? Incorrect type information on the
AST?
My understanding was that the check was to terminate the recursion, so as
to at
least avoid overflowing the C++ stack, and that any "bad" things that have
happened would already have signaled a bailout in the state of the visitor.
So I don't think doing a check beforehand fixes the actual bug (rather, it
hides
it) -- which seems to be that we do some other call(s) that can detect a
stack
overflow without checking for that condition after the call(s). We should
find
out which calls these are.
It would be great if we could somehow instrument the language to flag
missing
checks, but I don't have a good idea off-hand. Maybe returning a
MUST_USE_RESULT
of some auxiliary type with the check being the only way to consume that
type.
But that would be tedious for functions that also want to return a real
result.
https://codereview.chromium.org/110913004/
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