Calling PIR from a PMC

[William Coleda]

How does one call a PIR-defined sub from C?

My current best guess is, to invoke the PIR sub "Tcl::Joe":

PMC *invokeme;
STRING *Tcl,*joe;
Tcl = string_from_const_cstring(INTERP, "Tcl", 3);
joe = string_from_const_cstring(INTERP, "joe", 3);
invokeme = Parrot_find_global(INTERP, Tcl, joe);
VTABLE_invoke(INTERP,invokeme,????);

But I don't know what to put as the argument for "next" to VTABLE_invoke - I see some items in dynclasses/*.pmc use the string "next", the code seems to allow for NULL - neither of them seem to actually invoke my method. (a .sub with a single "print" statement)

Do I need to be setting up the calling conventions in my calling code? Is there some other step I'm missing? Is this already documented somewhere?

[Jeff Horwitz]

On Mon, 14 Mar 2005, William Coleda wrote:

> How does one call a PIR-defined sub from C?

use the Parrot_call_sub_* API.

here's how i do it in mod_parrot, using the Parrot_* datatypes and the
Parrot_call_sub_* API. some of the logic has been factored out into
different functions for code reuse, but you get the idea:

Parrot_PMC get_sub_pmc(Parrot_Interp interp, char *namespace, char *name)
{
Parrot_PMC sub;

sub = Parrot_find_global(
interp,
namespace ? MAKE_PARROT_STRING(namespace) : NULL,
MAKE_PARROT_STRING(name)
);
return(sub);
}

int modparrot_call_sub(Parrot_Interp interp, char *namespace, char *name,
int *ret)
{
Parrot_PMC sub;

sub = get_sub_pmc(interp, namespace, name);
if (!sub) {
return(0);
}
*ret = Parrot_call_sub_ret_int(interp, sub, "Iv");
return(1);
}

-jeff

[William Coleda]

Jeff Horwitz wrote:
> On Mon, 14 Mar 2005, William Coleda wrote:
>
>
>>How does one call a PIR-defined sub from C?
>
>
> use the Parrot_call_sub_* API.

Ah, thank you, much better.

Now, given the perldoc for src/extend.c,

"void* Parrot_call_sub(Parrot_INTERP interpreter, Parrot_PMC sub, const
char *signature, ...)"
Call a parrot subroutine the given function signature. The first
char in "signature" denotes the return value. Next chars are argu-
ments.

The return value of this function can be void or a pointer type.

If only the first character is the return value, how does one deal with subroutines that return multiple values?

[Leopold Toetsch]

William Coleda <wi...@coleda.com> wrote:

> If only the first character is the return value, how does one deal
> with subroutines that return multiple values?

Well, you can't access multiple return values from within the C
function, where you are calling the PIR code. OTOH, if the PIR code did
return more values, we should get them back to the caller.

We should probably have a new return signature for this, e.g.

"@" - collect all return values, stuff them into an array and return
that.

OTOH you could use Parrot_runops_fromc() and pick up return values from
the returned frame pointer C<bp>.

leo