Squawks of the Parrot

Let the thumping begin

I spent a chunk of this weekend working on the Pie-thon conversion setup. Since folks seem interested in this sort of thing (I'm not sure whether it's as a record of success or abject failure, so we just won't go there right now :) I figure I ought to note down what's going on--it's not like it'll make much difference one way or the other with the contest, so there's no harm as I see it.

There's also a new category for this if you're into that sort of thing. (Official trackback ping URL is http://www.sidhe.org/~dan/blog/mt-tb.cgi/253 according to MT) No RSS feed just for it. (And yes, I realize the "WTHI" feed is actually a glommed-together category feed, and I need to fix that too)

Anyway, here's where we stand so far.

I've been working with Simon Cozens' Python::Bytecode module as my starting point--it disassembles python bytecode to a readable text stream, pretty much the same way that the dis module in the python distribution does. Seemed to be a good place to start, given I know far more perl than python.

The module, unfortunately, only comes knowing about the v2.1 and 2.2 bytecode formats. Things have changed a bit for v2.3 and, while I've got a version I hacked up to try and load v2.3 bytecode, there's been no joy there so far--it gets to the magic number identification OK, but the bytecode past that it doesn't recognize, and a hexdump shows it being a bit different from 2.2 bytecode. Some poking around in the Python core has been instructive, but not enough that I've been able to get it going. (I expect that once I can get it to get to the actual code it'll work, but...) There may be a few extra constants in there now that I look at the hex dumps again. Hrm. Going to have to poke in the python source some more. (I now see the value of editors with function name completion, FWIW)

In the mean time, I've been taking a look at the dis module instead. This ships with python and provides disassembly services along with a command-line interface that'll take python source, compile it, and provide the disassembled bytecode. I've gotten a bit further with this, though it's got a serious limitation that's getting in the way--it only disassembles the first function in the source, and doesn't dump the constants out in a useful way. (Not that this is a bad thing as such. It's still quite useful) Still, a place to start.

I've also got the start of a conversion scheme from python bytecode ops to parrot ops. This has the additional issue of having to do stack to register scheme translation, which could be a big deal in hand-rolled code but I expect it won't be a problem here. I think I may well do at least one intermediate representation, though, rather than a direct conversion. We'll see.

I'll post the code for this stuff as I get it going.

Posted by Dan at May 17, 2004 11:15 AM | TrackBack (0)