Parent-Task:

• SR-710 Generate XCTestCaseProvider entries on Linux

blocks:

• SR-1676 Build SourceKit on Linux

Issue Description:

The sourcekitd/sourcekitd.h header uses __has_feature(blocks) to only define block-based APIs on platforms that support them. For some of these APIs, function pointer equivalents are also defined.

However, much of the internal implementation of SourceKit uses the block-based APIs. Therefore, SourceKit cannot build on any platform that does not have blocks – specifically, it does not build on Linux.

The following block-based APIs need function pointer equivalents, and SourceKit implementation callsites to these functions should use the function pointer APIs instead:

• sourcekitd_set_interrupted_connection_handler needs sourcekitd_set_interrupted_connection_handler_f

• sourcekitd_variant_dictionary_apply needs sourcekitd_variant_dictionary_apply_f

• sourcekitd_variant_array_apply needs sourcekitd_variant_array_apply_f

• sourcekitd_send_request needs sourcekitd_send_request_f

• sourcekitd_set_notification_handler needs sourcekitd_set_notification_handler_f

• sourcekitd_set_uid_handlers needs sourcekitd_set_uid_handlers_f

As far as I know, adding a function pointer API for a block-based API looks something like the following, using sourcekitd_set_notification_handler as an example:

// Instead of a block `sourcekitd_response_receiver_t`, define a function `sourcekitd_response_receiver_f_t`.
// Because functions can't capture stack variables, it's passed a context pointer.
typedef void (*sourcekitd_response_receiver_f_t)(sourcekitd_response_t resp, void *context);
// Define another function that takes the new function pointer type.
void sourcekitd_set_notification_handler_f(sourcekitd_response_receiver_f_t receiver);

It might be a good idea to create sub-tasks for each of these, although I'd like to confirm that this is a reasonable direction before we do that.