Re: [ooc-compiler] Handling C "in" parameters

[Stewart G. <sgr...@ii...>]

Hi August,

>> I suggest that you do something like this:
>>
>> PROCEDURE ["SDL_PollEvent"] PollEvent*(VAR event: Event): C.int;
>
> Yes, this is the ideal solution. I didn't know that VAR parameters and
> pointers were compatible in this case.

In this context, a VAR parameter is a kind of "enhanced" pointer since 
it can point to an object on the stack or the heap. For Oberon-2 
RECORDS, the compiler passes the pointer and an additional hidden 
argument which is its type descriptor. For heap-based records, it uses 
the type descriptor from the heap object. For stack-based records it 
uses the descriptor for the (static) type of the record.

For foreign "C" records, there is of course no type information. You 
can declare "VAR event [NIL_COMPAT]" which allows you to pass NIL as 
the reference for a VAR parameter.

> By the way, I have heard of a C header to Oberon-2 conversion tool
> called H2O. Do you know where I can get it?

Its in the CVS repository. Check this message for some details:
   http://sourceforge.net/mailarchive/message.php?msg_id=10766629

Since I'm also interested, I tried compiling the libsdl headers. The 
current CVS version of H2O handles version 1.2.7 of libsdl. By that, I 
mean that it compiles the "C" code, and produces compilable Oberon-2 
modules (with a couple of small manual changes). If you like, I can 
e-mail you the generated files. It needs a little work to be properly 
usable, but may save you some time over doing manual translation.

Cheers,
   Stewart