Re: Clarification on "Infinite parsing loops in IELR + LAC"

[akim]

Hi Adrian,

That would be a question for Joel, I don't know the details.

Le 2018-09-11 00:03, Adrian Vogelsgesang a écrit :
> Hi everyone,
>
> From what I understand reading the bison documentation and some of the
> linked publications,
> I should probably be using IELR in combination with 
> Lookahead-Correction
>
> However, I stumbled across a warning in section 5.8.3 (“LAC”) in the
> bison documentation
> (https://www.gnu.org/software/bison/manual/bison.html#LAC):
> > IELR plus LAC does have one shortcoming relative to canonical LR. Some 
> > parsers generated by Bison
> > can loop infinitely. LAC does not fix infinite parsing loops that 
> > occur between encountering a syntax
> > error and detecting it, but enabling canonical LR or disabling default 
> > reductions sometimes does.
>
> This sounds quite frightening to me and I am not sure if LAC is
> actually something I should be using.
> Could someone clarify that part of the documentation for me?
>
> In particular, I would be interested in the following points:
> * The documentation only mentions IELR + LAC, but what about LALR + 
> LAC?
> * "LAC *does not fix* infinite parsing loops" -> this sounds as if
> these infinite parsing loops would also exist without LAC?
> * When exactly do those infinite loops occur? How can I avoid them?
>
> Best,
> Adrian
>
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