[pcre-dev] [Bug 1803] segfault in pcre jit when running twig…

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Címzett: pcre-dev
Tárgy: [pcre-dev] [Bug 1803] segfault in pcre jit when running twig test suite (PHP7)
https://bugs.exim.org/show_bug.cgi?id=1803

--- Comment #33 from Zoltan Herczeg <hzmester@???> ---
> I grabbed a lot of gdb output just now, trying to narrow down when
> size_offsets location gets trashed to 0. I noticed that offsetcount does,
> inside one of the jit functions, get set to 2, but it's back to 3 in the
> caller, until it returns to the PHP code. At which point size_offsets has
> been set to 0... I'm going to put a watchpoint on the address of
> size_offsets to see if I can see what actually is writing to it.


Thank you, I check it.

What I still don't get, if size_offsets is zero, and count is zero

if (count == 0) {
    php_error_docref(NULL,E_NOTICE, "Matched, but too many substrings");
    count = size_offsets/3;
}


then count should be still zero after this point, how could this be true:

if (count > 0 && (offsets[1] - offsets[0] >= 0))

Perhaps GCC is (too) clever here, and realized that size_offsets must be >= 3
since it is computed in the following way:

size_offsets = (pce->capture_count + 1) * 3;

and optimized out the count > 0 part. I saw such things before...

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