[perl #122283] Possible regexp memory explosion in 5.20.0

Further to Hugo's report...

I have now had the opportunity to investigate the problem, and have concluded that this has nothing to do with Regexp::Grammars per se, except that R::G is generating the enormous regex that 5.20 is failing to compile.

The attached example (constructed by removing all the R::G syntactic sugar from Hugo's original) does not make use of Regex::Grammars at all, and still leaks endlessly under 5.20...whereas it compiles repidly and without complaint under all of:

     5.10.1
     5.12.5
     5.14.4
     5.16.3
     5.18.2

I hope this additional information may be of help in tracking down the regression. 

Damian

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via perlbug:  queue: perl5 status: new
https://rt.perl.org/Ticket/Display.html?id=122283

• [perl #122283] Possible regexp memory explosion in 5.20.0 by Damian Conway via RT
• Re: [perl #122283] Possible regexp memory explosion in 5.20.0 by Aaron Crane
• Re: [perl #122283] Possible regexp memory explosion in 5.20.0 by Dave Mitchell
• Re: [perl #122283] Possible regexp memory explosion in 5.20.0 by demerphq
• Re: [perl #122283] Possible regexp memory explosion in 5.20.0 by demerphq
• Re: [perl #122283] Possible regexp memory explosion in 5.20.0 by Karl Williamson
• Re: [perl #122283] Possible regexp memory explosion in 5.20.0 by Dave Mitchell
• Re: [perl #122283] Possible regexp memory explosion in 5.20.0 by demerphq
• [perl #122283] Possible regexp memory explosion in 5.20.0 by Hugo van der Sanden
• Re: [perl #122283] Possible regexp memory explosion in 5.20.0 by demerphq
• Re: [perl #122283] Possible regexp memory explosion in 5.20.0 by hv