[C2hs] Re: support for 6.4

[Manuel M T Chakravarty]

Duncan Coutts:
> On Mon, 2005-05-23 at 00:42 +0100, Duncan Coutts wrote:
> From my brief experiment the 9.7 Mb file when deserialised into the heap
> takes just over 50Mb of heap space and top reported 47Mb RSS.
> 
> I tried another experiment and found that the parsing phase by itself
> required over 250Mb of heap space. By the time it got to the name
> analysis it requires over 350Mb.
> 
> So from that it looks to me that the parser could be improved. The
> lexer/parser could be swapped out for another implementation without
> affecting any other module.
> 
> Perhaps we should look at one based on Alex & Happy. Happy can do
> monadic parsers which would allow it to maintain the set of identifiers
> needed when parsing C. Alex & Happy can produce pure Haskell98 code (or
> ghc specific code for better performance) so the portability of c2hs
> would not be affected - unlike our binary serialisation patches which
> are use various ghc'isms.

An Alex/Happy parser would be an option if it improves matters
significantly.  If you or anybody else has a go at it, please follow the
C language definition closely, as does the existing lexer and parser
(with comments stating to which sections in K&R the individual
productions relate).  Moreover, the module
c2hs/base/syntax/ParserMonad.hs already provides a monad suitable for
Happy.

Manuel