[pypy-dev] llvm and externs

[Richard Emslie]

Hi Chris,

On Thu, 27 Oct 2005, Chris Lattner wrote:
> On Thu, 27 Oct 2005, Eric van Riet Paap wrote:
>> On Thursday 27 October 2005 07:21, Chris Lattner wrote:
>>> On Thu, 27 Oct 2005, Richard Emslie wrote:
>>>> Ooops - sorry about the horrible subject in last mail (it's late)
>>> Which externs do you need?  Are these for system prototypes or pypy
>>> functions?
>> 
>> With externs in this context we mean functions we need to call from the 
>> O.S.
>> (libc). Plus a little wrapper code to make it compatible with Python.
>> (Sometimes raise an exception instead of returning an errorcode, etc.)
>
> Using the C front-end to parse C headers is a pretty big hammer for this 
> problem.  In particular:

Yes this is what we do currently do.  We were going to go one step further 
and preprocess the file locally and then send that to a remote server. 
But I am not sure of the merits of this and whether it would work at all.

>
>> Now listdir() uses opaque (dont know if you introduced this or someone 
>> else) - and llvm doesnt have proper support for opaque types... yet. So we 
>> cannot compile pypy right now.
>
> I'm not sure is considered to be "proper support" for opaque types, but we 
> certainly do support them.  I'm not sure what the prototype for listdir is 
> supposed to be, but you should always be able to use something like this 
> (assuming it takes a pointer to some structure type):
>
> declare void %listdir(opaque*)
>
> or:
>
> declare void %listdir(sbyte*)
>

Sorry for the ambiguity here.  In RPython there is an Opaque low level 
type.  I was saying the llvm backend was not complete (basically 
initialisation code).  Right now we are effectively translating to your 
latter suggestion (sbyte *), although will probably change it to opaque* 
since they are already called that in rpython. :-)

> LLVM cares that it is a pointer, but as long as you're not directly accessing 
> any of the members of the struct, it doesn't care what it is a pointer to.
>

That's where I got to (eventually) last night! ;-) pypy should compile 
again with the llvm backend (although I havent been able to test it)

Thanks very much for the insights & sorry for the confusion.

Cheers,
Richard