Re: Parser rewritting

[Chris Moller <cmoller at redhat dot com>]

On 04/08/10 15:21, Tom Tromey wrote:
> Chris>  A lot of years ago I wrote a fairly elaborate parser using
> Chris>  antlr--definitely a cool tool and I recommend you consider it.
>
> One thing to ensure is that the antlr output is GPL-compatible.
> If not, we can't use it.
>    

antlr.org says that ANTLR itself is under "The BSD License," which looks 
to like a small subset of GPLv2, but IANAL.  I couldn't find anything 
about licensing for the generated code.

http://www.antlr.org/wiki/display/Mantra/License


> Chris>  Just as an example, I've attached a rudimentary antlr grammar that
> Chris>  parses a subset of C/C++ decls
>
> We only need expressions.
>
> Chris>  Anyway, it's probably worth considering.
>
> While I still think it makes the most sense to mimic g++, I am open to
> other solutions that are powerful enough.
>
> Another thing worth considering is bison's GLR mode.  This has the
> advantage that we wouldn't actually need to rewrite the whole parser, we
> could just start by tweaking it.
>
> Using tools that generate code is problematic in GDB, because people
> complain about every new dependency.  Even requiring bison will probably
> generate complaints, because AFAIK some people still do their builds
> with byacc.  Maybe we could check in the generated code, though.
>    

With one exception, ANTLR, including v3, under at least Fedora--I don't 
know about RHEL.  The exception is the v3 C target-language support, 
which I had to install separately, but I expect it could be included in 
the antlrv3 package.

The generated code is kinda big.  The source for the antlr C/C++ 
expression parser I wrote totals 737 lines, about 500 of which is C 
support code--the antlr grammar is only 239 lines.  But that 239 lines 
gets turned into about 8800 lines of combined lexer and parser.

> Tom
>