checking for interupts

[romainfrancois]

Client packages need a clean way to check for interupts, i.e. the documented way (as of Writing R extensions) would potentially violate C++ destructors, meaning leaks, and potentially objects that are forever protected from the GC ...

In a R-devel thread, Simon posted this code:

static void chkIntFn(void *dummy) {
  R_CheckUserInterrupt();
}

// this will call the above in a top-level context so it won't longjmp-out of your context
bool checkInterrupt() {
  return (R_ToplevelExec(chkIntFn, NULL) == FALSE);
}

// your code somewhere ...
if (checkInterrupt()) { // user interrupted ... }

[jjallaire]

We could have a function that throws a C++ exception in the case that checkInterrupt returns true. This could then be caught in the BEGIN/END_CPP macro construct and converted to a stock R_CheckUserInterrupt call (or Rf_jump_to_toplevel call)

[romainfrancois]

That makes sense and is inline with what we do with keeping both C++ exceptions and R conditions work together.

Although Simon says:

The problem with it is that it will eat all
errors, even if they were not yours (e.g. those resulting from events triggered the event loop), so I would
not recommend it for general use. 

[coatless]

This issue was addressed in PR #91 .

Please close. (Tagged #506)