Re: [Caml-list] debugging an ocamlyacc parser

[Xavier Leroy <xleroy@pauillac.inria.fr>]

> Well, while my current ocamlyacc parser seems to be working pretty well,
> I'm just wondering if there's a debug mode available for
> ocamlyacc-generated parsers, like the debugging mode that Bison uses
> when you do a #define YYDEBUG, printing out all the states the parser
> goes through as it receives tokens from the lexer, so along with the
> generated y.output file I can see how it's working (or not working as
> the case may be).

There is such a debugging mode in the pushdown automaton used to
execute ocamlyacc parsers, but it is not easily accessible.

You need to build the "debug" version of the bytecode interpreter (cd
runtime ; make ocamlrund), then run your bytecode executable with
"ocamlrund -P myprog".

You then get a trace of shift and reduce actions; tokens read are also
printed, but in such a low-level format that it's nearly useless...

I agree this tracing facility should be made better at some point,
although printing tokens correctly is difficult in general.

- Xavier Leroy
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