Re: [pcre-dev] Remove some restrictions of lookbehind assert…

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Autor: ph10
Data:  
Para: Zoltán Herczeg
CC: pcre-dev@exim.org
Assunto: Re: [pcre-dev] Remove some restrictions of lookbehind assertions
On Tue, 30 Jul 2019, Zoltán Herczeg wrote:

> > (*MOVE) is a small addition and solves ND's non-atomic assertion
> > requirement. Perhaps we can just start with (*MOVE).
>
> Yes, if we choose this option to implement.


It occurs to me that (*MOVE) gives scope for infinite loops:

(*MARK:X)(?:abc(*MOVE:X))+

That would loop for ever, wouldn't it? It seems rather a dangerous thing
to implement, unless there is some easy way to catch such cases.

I am beginning to agree with you about "non-atomic assertions" not
really being assertions. Perhaps they could be renamed:

(*napla: becomes (*prg: position reset group
(*naplb: becomes (*prgb: position reset group behind

or even abolish (*naplb: altogether. In addition, these must be treated
as normal groups, not as assertion groups. What happens when they are
repeated must be defined - or maybe they should not be allowed to
repeat, because once again that might be an easy way to infinite loops.

> I would like to hear others opinion though.


So would I!

Philip

--
Philip Hazel