On Oct-26, Melvin Smith wrote:
> At 06:25 PM 10/26/2003 -0800, Steve Fink wrote:
> > .pcc_sub _main prototyped
> > .pcc_begin_return
> > .return 10
> > .return 20
> > .pcc_end_return
> > .end
>
> It is still the same issue. This code explicitly mixes 2 call conventions.
> _main is declared as prototyped so it will return 1 in I0 which signals that
> it is returning its values in registers in prototyped convention. Your
> call explicitly calls in non_prototyped mode which does not generate any
> code to check the return convention since you are saying by your code
> that you _know_ what the call convention is.
Oops, I meant to leave the "prototyped" off of the _main sub. This
behaves indistinguishably from declaring it prototyped; it seg faults
if called non_prototyped. I believe it's supposed to work when called
with either style.
Sorry for the bad example.
Likewise, if I declare the .pcc_sub to be non_prototyped (so that both
the call and declaration are non_prototyped), I get the same error:
.sub _main
.local Sub myfunc
myfunc = newsub _myfunc
.pcc_begin non_prototyped
.pcc_call myfunc
ret:
.result $I0
.result $I1
.pcc_end
print "Returned "
print $I0
print ","
print $I1
print "\n"
end
.end
.pcc_sub _myfunc non_prototyped
.pcc_begin_return
.return 10
.return 20
.pcc_end_return
.end
% ./perl6 -Rt mini.imc
.
.
.
PC=60; OP=38 (invoke_p); ARGS=(P1=RetContinuation=PMC(0x40c04998))
PC=21; OP=1003 (restoretop)
PC=22; OP=801 (shift_i_p); ARGS=(I17=0, P3=NULL)
Error: '/home/sfink/parrot/parrot -t -r mini.imc ' failed
died with signal 11 (SIGSEGV)
> However, I see your point. To be orthogonal would suggest that we
> implement the same feature for .pcc_call that we do for the .pcc_sub
> declaration. If you left off the calling convention to .pcc_call it
> would generate code to check for either. Although this would really
> bloat the code, it might be wise to support the feature for some
> instances.
No, sorry, my bad example obscured the issue. I was not asking for a
.pcc_begin that works in either case; I just want it to be possible to
call a subroutine without a prototype and have it successfully return
values. True, I would also like to be able to call the same subroutine
*with* a prototype in another call site, but that is already
implemented. I don't think allowing people to leave off the
{non_,}prototyped declaration from .pcc_begin provides anything but
superficial syntactic orthogonality; a call site really ought to know
whether it can see the prototype of what it's calling or not! (Well...
except I sometimes call non_prototyped even when I know the prototype,
because pdd03 calling convention prototypes don't handle everything in
a Perl6 prototype. But that's irrelevant here.)
My brain doesn't seem to be working all that well this weekend...
I'll throw in one more thing just because I know a certain Mr. P.
Cawley dearly loves people to pile unrelated things into a single
thread: could there be a way to expose which continuation to invoke
when returning from a routine? In a regex, I'd really like a rule to
be invoked with a "success" continuation and a "fail, so backtrack"
continuation. And possibly with some more extreme failure
continuations for cuts and commits and things. But right now the
return continuation in P1 is hidden inside the PCC mechanism. (I guess
I could just manually overwrite P1, but that seems like it's working
against imcc rather than with it.)
I'm faking it for now by returning a boolean status code, but that
doesn't really feel like the "right" solution.
