[cffi-devel] cffi-libffi funcall path and :string

[Liam Healy]

OK, I've done this in master; there is a new method for foreign-type-alias
in expand-to-foreign-dyn-indirect.  Ryan, can you test this version, and,
if possible, post a simple example (whether it worked or not) that we can
add to cffi-tests.  Thank you.

Liam

On Mon, May 28, 2012 at 11:33 PM, Liam Healy <lnp at healy.washington.dc.us>wrote:

> On Sun, May 27, 2012 at 4:48 PM, Luís Oliveira <luismbo at gmail.com> wrote:
>
>> On Sun, May 27, 2012 at 9:15 PM, Luís Oliveira <luismbo at gmail.com> wrote:
>> > Did you notice the function lisp-string-to-foreign? Seems like a
>> > cleaner way to implement translate-into-foreign-memory.
>>
>> More importantly, how can you be translating a string without
>> performing allocation in this case? Also, in general,
>> translate-into-foreign-memory for strings should definitely refuse to
>> accept string types without an explicit size. (Which is not
>> implemented yet, IIRC.)
>>
>> In any case, why does Ryan's example need translate-into-foreign-memory?
>
>
> Yeah, the new method is the wrong thing, I need to revert this change.
> When foreign-funcall-form is called and fsbvp=T, it calls translate-objects
> with indirect=T, which in turn calls #'expand-to-foreign-dyn-indirect on
> each of the arguments.  When an argument is a foreign-string-type, the
> trouble begins.   The foreign string is represented by a pointer, as
> indicated by the (:actual-type :pointer) in the define-foreign-type.  All
> libffi really needs is a pointer to the pointer, and there is a method for
> expand-to-foreign-dyn-indirect for foreign-pointer-type, but
> foreign-string-type is not a subclass of foreign-pointer-type.
>
> It seems like the resolution is to define a method for
> expand-to-foreign-dyn-indirect for the foreign-type-alias class that does a
> recursive call using the actual-type.  Does that make sense?  As a side
> point, expand-to-foreign-dyn has a similar method but it is defined for
> enhanced-typedef (subclass chain: enhanced-typedef < foreign-typedef <
> foreign-type-alias); is there any reason why that method shouldn't be
> defined for foreign-type-alias instead?
>
> Liam
>
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