Re: Undefined symbols for deferred bindings

[Janus Weil <janus at gcc dot gnu dot org>]

Hi Damian,

> The code below compiles correctly (hooray!), but the linker can't find the
> symbols related to the deferred bindings. ?It's possible there's a problem
> in my link line, so you might jump straight to the bottom. ?Otherwise, foo
> defines an abstract type (as in my previous posting); bar extends foo and
> overrides foo's deferred bindings; and main declares a bar object and passes
> it to the "rescale" procedure inside foo_module.

sorry for the late answer. I don't think there's a problem in your
link line. Rather I would say deffered TBPs are just an unimplemented
feature for now (if I'm not mistaken). Hopefully that should change
once Paul's new patch for dynamic dispatch has landed on the branch.


> Undefined symbols:
> ?"_assign_interface_", referenced from:
> ? ? ?___foo_module_MOD_rescale in foo.o
> ?"_times_interface_", referenced from:
> ? ? ?___foo_module_MOD_rescale in foo.o
> ld: symbol(s) not found

Trying to explain these error messages: We had support for ('static')
TBPs before we had polymorphism. In this old implementation, calling a
TBP would be translated statically to a call of the bound procedure.
Since for deferred TBPs, we have nothing that is bound to it, we just
generate a call to the interface symbol (so that at least the call can
be checked for correctness etc). But, since this is just an interface,
not a real procedure, it does not actually exist and linking fails. At
least that is what I think is happening. Paul or Daniel may be able to
tell you more about this.

Cheers,
Janus