Re: Proposal: Finally statement of function

[Glenn Maynard <glenn@...>]

On Fri, Feb 09, 2007 at 10:49:48PM -0500, Rici Lake wrote:
> That's exactly what it does (or would do).
> 
> This is how Lua works (currently) when an error is thrown:
> 
> 1) the error function is called immediately when an
> error is encountered, so it sees the current stack.
> 
> 2) Then upvalues are closed back to the last pcall() (or to the
> beginning of the stack.) That's necessary because the stack
> is about to be popped back to that pcall().
> 
> 3) Finally, the stack is popped back to the pcall, and control
> is returned to the pcall.
> 
> That's precisely why I think that the upvalue closure
> mechanism can be used as well to implement finalizers.
> The proposed finalizer mechanism runs the finalizer during
> the upvalue closure sequence, which means it will run
> at step 2, above, ensuring that the finalizer executes
> before the pcall is returned to.

In this case, could it be possible to have a C API to add a cleanup
function to the running CFunction (rather than messing with the error
handler) through the same mechanism (perhaps requiring reserving
a closure slot in advance, though ideally not)?

-- 
Glenn Maynard