Integer arguments passed to inferior's functions

Integer arguments passed to inferior's functions

[Eli Zaretskii]

If I type

  (gdb) call foo(1)

what will be the type of the argument GDB will pass to `foo'?  Will
GDB look up the function signature or will it use some default?.  If
the former, what happens when the signature is unknown or unavailable?
If the latter, how is that default computed? does it depend on the
inferior's architecture, for instance?

Apologies if this is in the manual and I missed it; at least the node
"Calling" keeps silent about this issue.

TIA

Re: Integer arguments passed to inferior's functions

[Jan Kratochvil]

On Sun, 30 Oct 2011 07:38:44 +0100, Eli Zaretskii wrote:
> If I type
> 
>   (gdb) call foo(1)
> 
> what will be the type of the argument GDB will pass to `foo'?  Will
> GDB look up the function signature or will it use some default?.

Yes, it looks up the function signature, see the value_arg_coerce call in
call_function_by_hand.  It uses the passed parameter (typeof (1) -> int here)
if the parameter is after the known count of parameter types.


> If the former, what happens when the signature is unknown or unavailable?

The known parameters count is 0 in such case.


> If the latter, how is that default computed?

value_type of that value (1 here, therefore int).


> does it depend on the inferior's architecture, for instance?

After all these types are determined you are right the types are further
promoted depending on the arch, by gdbarch_push_dummy_call.


Thanks,
Jan

Re: Integer arguments passed to inferior's functions

[Eli Zaretskii]

> Date: Sun, 30 Oct 2011 14:30:01 +0100
> From: Jan Kratochvil <jan.kratochvil@redhat.com>
> Cc: gdb@sourceware.org
> 
> On Sun, 30 Oct 2011 07:38:44 +0100, Eli Zaretskii wrote:
> > If I type
> > 
> >   (gdb) call foo(1)
> > 
> > what will be the type of the argument GDB will pass to `foo'?  Will
> > GDB look up the function signature or will it use some default?.
> 
> Yes, it looks up the function signature, see the value_arg_coerce call in
> call_function_by_hand.  It uses the passed parameter (typeof (1) -> int here)
> if the parameter is after the known count of parameter types.

And 1 is an int because it has no l/ll qualifier?

> > does it depend on the inferior's architecture, for instance?
> 
> After all these types are determined you are right the types are further
> promoted depending on the arch, by gdbarch_push_dummy_call.

Thanks.

Re: Integer arguments passed to inferior's functions

[Jan Kratochvil]

On Sun, 30 Oct 2011 19:17:07 +0100, Eli Zaretskii wrote:
> And 1 is an int because it has no l/ll qualifier?

I think so:

(gdb) ptype 1
type = int
(gdb) ptype 1L
type = long
(gdb) ptype 1LL
type = long long


Regards,
Jan