Re: [9fans] calling function with (variable number of) parameters

["Douglas A. Gwyn" <DAGwyn@null.net>]

Latchesar Ionkov wrote:
> I am trying to write a function
>         int callf(void *f, int nargs, int *args)
> f is a pointer to a function of a type
>         int f(int, int, int, ..., int)

No, it isn't; at least, not as you have declared callf.

Also, that is not a proper variadic declaration for the type of f.
I think what you mean is that the actual function definition uses
a *fixed* number of arguments, different for different values of
f, and you're hoping that the passed nargs happens to be
consistent with the function that the passed f points to.

> callf should copy nargs number of ints from args to the stack and call f,
> and then return f's return value.

> Is this possible with Plan9 C calling convention? ...
> Do I miss something? Any ideas how to implement it?

It's an abuse of C under any linkage convention.

> Unfortunately I don't have any control on the requirements or the way f gets
> its parameters. If there is no way to do it for any number of args, I'll
> limit nargs (and hope nobody will write function with more than 15
> arguments) and will modify SP with a constant value.

That will probably be your best bet.
Other solutions would require changes to the interface.