[fpc-pascal] syscalls and fpc

Marco van de Voort marcov at stack.nl
Fri Feb 15 19:43:03 CET 2008

> Micha Nelissen schreef:
> > ik wrote:
> >> Actually the assembler is not that hard to understand :)
> >> My point is, that I don't like the idea of 7 or 20 or 100 amount of
> >> parameters to give answer to every need. I think we should find a
> >> better way to implement it, like var args in C or open array in
> >> pascal...
> > 
> > The linux kernel interface is always using registers, and since there
> > are a limited amount of registers, there is a max. number of arguments.
> > IIRC the maximum is 6, i386 limited: eax, ebx, ecx, edx, esi, edi, ebp.
> Fortunately I studied mathematics, so I can count the mentioned 
> registers: 7.

Then you should also see dangerous hidden assumptions:

Not all parameters occupy a single register. off_t for 64-bit fs calls e.g.

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