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Postings from October 2016
On 19 October 2016 at 09:22, demerphq <demerphq@gmail.com> wrote:
> On 18 Oct 2016 23:46, "Father Chrysostomos via RT"
> <perlbug-followup@perl.org> wrote:
>>
>> On Tue Oct 18 04:08:30 2016, demerphq wrote:
>> > On 18 October 2016 at 12:03, Hugo van der Sanden via RT
>> > <perlbug-followup@perl.org> wrote:
>> > > On Tue Oct 18 02:30:01 2016, demerphq wrote:
>> > >> I think we can fix it by checking PL_curpm against PL_reg_curpm when
>> > >> we do the empty pattern check; running tests now.
>> > >
>> > > And do what? Even if they're the same, it still might also
>> > > legitimately be the last successful match, no?
>> >
>> > No I don't think so, and all the tests pass.
>> >
>> > As far as I can tell PL_reg_curpm is a special opcode which we use
>> > when we are setting up PL_curpm before executing a (?{...}) or (??{
>> > ... }) code block so that things like $1 and stuff like that point at
>> > the current pattern. Once the code is executed PL_curpm is unwound to
>> > no longer point at PL_reg_curpm. Essentially the problem comes down to
>> > PL_curpm being the place where things like $1 and friends are derived,
>> > as well as how we find the pattern for the last successful match, but
>> > inside of a (?{ ... }) we want $1 to point at the *current* pattern,
>> > not the *last* successfully matched one. This conflict currently
>> > causes use of the empty pattern in a code block to point at the
>> > pattern that contains the code, and trigger infinite recursion. So to
>> > fix this I think we would have to split PL_curpm in two, and have one
>> > var for $1 and friends representing "the last successful matched
>> > pattern or when in a regex code construct the currently executing
>> > pattern", and another for "last successful matched pattern" which
>> > would be use by the empty pattern magic.
>> >
>> > On the other hand we can simply forbid the use of the empty pattern
>> > inside of a regex code block and have a much simpler patch. :-)
>>
>> PL_curpm does far too many things. This is not the only bug that results.
>
> Can you expand on that thought a bit please?
BTW, I pushed a patch to forbid use of the empty pattern inside of
regex code blocks.
Once I understand what else you worry about with PL_curpm I will do a
patch to make it work properly.
But I figure a run time catchable fatal exception is better than a C
stack overflow until we can make it work properly.
Yves
--
perl -Mre=debug -e "/just|another|perl|hacker/"
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