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bug#24358: 25.1.50; re-search-forward errors with "Variable binding dept


From: Eli Zaretskii
Subject: bug#24358: 25.1.50; re-search-forward errors with "Variable binding depth exceeds max-specpdl-size"
Date: Mon, 24 Oct 2016 16:39:55 +0300

> From: address@hidden
> Cc: address@hidden,  address@hidden
> Date: Mon, 24 Oct 2016 09:29:21 -0400
> 
> >   regstart[*p] = d;
> >   [...]
> >   regs->start[reg] = POINTER_TO_OFFSET (regstart[reg]);
> >
> > POINTER_TO_OFFSET assumes that the pointer in regstart[reg] is
> > consistent with the current base address of the string into which it
> > points.  Did you study this aspect of regex.c when you decided which
> > values need to be affected by relocation?
> 
> I did not look at that before, but looking now, I don't see why it would
> be a problem.  I put the base address updating code around the only
> place where malloc may be called, so string1 and string2 (which
> POINTER_TO_OFFSET uses) should always be consistent with the base
> address (unless there is some other malloc call that I missed?).

What bothers me is this: could it be that relocation happens between
the first and the second line above?  If it can, then what
POINTER_TO_OFFSET does will be inconsistent with the base address at
the time regstart[*p] was assigned the value of d.

The code runs in a loop, or so it seems, so it's hard to reason about
time sequences.

But I'm not saying I clearly see a problem, just that I fear there
might be one.  If your reading of the code is that it cannot happen,
I'm happy.

Thanks.





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