Hi Brian -
This won't work very well right now since Chapel's mechanism
for capturing functions is built upon classes and virtual
method calls - and also since currently the C interoperability
support doesn't understand function pointers.
I'd like to fix both of those things....
In the mean time, I think that the best you can do is to:
* declare an extern proc in Chapel
* create a C function calling the extern proc
* tell Chapel that the C function is an opaque
Here is an example:
$ cat function_ptr.chpl
export proc proc_one() { writeln("in proc_one"); }
proc_one();
extern var call_proc_one:opaque;
extern proc call_fn_ptr(x);
call_fn_ptr(call_proc_one);
$ cat function_ptr.h
void proc_one(void);
static void call_proc_one(void) { proc_one(); }
static void call_fn_ptr(void (*fn)(void)) { fn(); }
$ chpl function_ptr.chpl function_ptr.h
$ ./a.out
in proc_one
in proc_one
Does this workaround solve your problem?
Cheers,
-michael
On 4/15/15, 12:14 PM, "Brian Guarraci" <[email protected]> wrote:
>Hi,
>
>
>What's the best way to declare an external C function that takes a
>function pointer? I want to pass a Chapel implemented function or an
>externally implemented function. I've done some research and experiments
>and haven't found a good solution yet.
>
>
>I originally (and naively) began with something like this in the Chapel
>module:
>
>
>proc ev_io_init_fn(ref loop: ev_loop_t, ref io: ev_io_t, x: c_int);
>extern proc ev_io_init(ref io: ev_io_t, ref fn: ev_io_init_fn, fd:
>ev_fd_t, events: ev_events_t);
>
>
>
>and then in chpl:
>
>
>export proc accept_cb(ref loop: ev_loop_t, ref watcher: ev_io_t, revents:
>c_int) {
>// do work
>}
>
>
>
>ev_io_init(w_accept, accept_cb, sd, EV_READ);
>
>
>
>but this (and similar approaches) will produce a compilation error akin
>to:
>
>
>chapel/chpl_tcp_server.chpl:38: error: unresolved call
>'ev_io_init(c_ptr(ev_io_t),
>chpl__fcf_type__ref_ev_loop_t__ref_ev_io_t_int32_t_void, int(32),
>int(32))' [functionResolution.cpp:2448]
>chapel/LibEv.chpl:75: note: candidates are: ev_io_init(io:
>c_ptr(ev_io_t), ref fn: ev_io_init_fn, fd: ev_fd_t, events: ev_events_t)
>[128267] [functionResolution.cpp:2463]
>
>
>
>
>Thanks!
>Brian
>
>
>
>
>
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