Callback on a CLang code block?

[srs]

Hi.

I am trying to call a method on OSX that takes a closure (CLang Block) as an argument. The method is xpc_connection_set_event_handler and the signature is as follows:

typedef void (*xpc_connection_handler_t)(xpc_connection_t connection);

typedef void (^xpc_handler_t)(xpc_object_t object);

void xpc_connection_set_event_handler(xpc_connection_t connection, xpc_handler_t handler); 

Right now I am calling it using a JNA Callback but that does not seem to work. Anyone that have done the same or similar calling to a closure (or code block)?

BR,
Sten Roger

[twall]

JNA doesn’t have any built-in awareness of clang blocks. You might be able to manually construct the required data to pass as an argument, but that would require delving into the runtime specifics of the blocks implementation.

JNA will create a stack-based code stub, the address of which is used as a function pointer and which, when run, transfers execution to the associated JNA Callback.

On Dec 31, 2015, at 5:12 PM, Sten Roger Sandvik [email protected] wrote:

Hi.

I am trying to call a method on OSX that takes a closure (CLang Block) as an argument. The method is xpc_connection_set_event_handler and the signature is as follows:

typedef void (*xpc_connection_handler_t)(xpc_connection_t connection);

typedef void (^xpc_handler_t)(xpc_object_t object);

void xpc_connection_set_event_handler(xpc_connection_t connection, xpc_handler_t handler);

Right now I am calling it using a JNA Callback but that does not seem to work. Anyone that have done the same or similar calling to a closure (or code block)?

BR,
Sten Roger

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[srs]

Thanks.

Well, it seems to me that I need to do some plain JNI code here. Have tried to construct the code-block struct and pass that without any luck. Maybe I'm missing some pieces here and there.

BR,
Sten Roger

[ghazel]

It would be pretty helpful for JNA to support clang blocks. Creating the struct and code stub is totally possible, here's an example using libffi just like JNA does: https://www.mikeash.com/pyblog/friday-qa-2011-05-06-a-tour-of-mablockclosure.html

[twall]

PRs are welcome.

[dkocher]

I would like to fund development of this implementation. Please reach out if interested to make this happen.

[dkocher]

@twall I would like to see this issue reopened to keep it as a label:"feature request".