Re: Thinking (again) about an Objective-C bridge

Rob,

I've looked at your bridge before.  In Gwydion, you just used call-out to
directly invoke stuff, so there wasn't a Dylan level syntax for doing an
arbitrary message send.  You had a script (i2d) that read through the
Objective C headers and generated bindings, with each one generating the
required call-outs.

The equivalent approach in Open Dylan using %call-c-function would be
something like:

  let c = objc/get-class("NSObject");
  let s = objc/register-selector("alloc");
  let o
    = primitive-wrap-machine-word
        (%call-c-function("objc_msgSend")
              (id :: <raw-machine-word>, sel :: <raw-machine-word>)
           => (obj :: <raw-machine-word>)
            (primitive-unwrap-machine-word(c.raw-class),
             primitive-unwrap-machine-word(s.raw-selector))
        end);

That's great and that works. However, once you go and add another
invocation with a different signature, like this:

  let s2 = objc/register-selector("alloc2");
  let o2
    = primitive-wrap-machine-word
        (%call-c-function("objc_msgSend")
              (id :: <raw-machine-word>, sel :: <raw-machine-word>, val ::
<raw-integer>)
           => (obj :: <raw-machine-word>)
            (primitive-unwrap-machine-word(c.raw-class),
             primitive-unwrap-machine-word(s2.raw-selector),
             integer-to-raw(3))
        end);

You'll end up with compile failures like this:

/Users/bruce/Development/dylan/objc-dylan/_build/build/objc-test-suite-app/../objc-test-suite/objc-test-suite.c:200:14:
 error: conflicting types for 'objc_msgSend'

extern DWORD objc_msgSend (DWORD, DWORD, DSINT);
             ^

/Users/bruce/Development/dylan/objc-dylan/_build/build/objc-test-suite-app/../objc-test-suite/objc-test-suite.c:199:14:
note: previous declaration
is here

extern DWORD objc_msgSend (DWORD, DWORD);
             ^

/Users/bruce/Development/dylan/objc-dylan/_build/build/objc-test-suite-app/../objc-test-suite/objc-test-suite.c:1086:24:
error: too many arguments to function call, expected 2, have 3

  objc_msgSend(T8, T9, T11);
  ~~~~~~~~~~~~         ^~~

/Users/bruce/Development/dylan/objc-dylan/_build/build/objc-test-suite-app/../objc-test-suite/objc-test-suite.c:199:1:
note: 'o
bjc_msgSend' declared here

extern DWORD objc_msgSend (DWORD, DWORD);
^


This is because the generated C specifies the prototype and 2 different
signatures means you get conflicting prototypes.  (We don't support varargs
as far as I can tell.)  We could hack things to emit a prototype without
any args taking advantage of the special meaning of void objc_msgSend() in
C, but that's not going to help us deal with different return values.

That's why I see things being somewhat difficult and the best approach
being to extend the compiler to lend a hand.

 - Bruce



On Fri, Jun 14, 2013 at 5:48 PM, Rob Myers <[email protected]> wrote:

> On 14/06/13 04:25, Bruce Hoult wrote:
>
>> Ideally, what you want is:
>>
>> - grab the symbols for the method and additional argument names
>> - convert to strings and concatenate
>> - create a global variable with that name (prefixed) to hold the
>> selector value.
>> - add the var and string to a hash table (or generate code) to look up
>> the selector value at program startup
>>
>
> Yes that sounds good.
>
> I wrote an Objective-C bridge for Gwydion, the notes may be useful:
>
> https://github.com/dylan-**hackers/GD_2_4/tree/master/**platform/cocoa<https://github.com/dylan-hackers/GD_2_4/tree/master/platform/cocoa>
>
> - Rob.
>
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> hackers mailing list
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