[deanfranks]

It would be ugly. For many architectures, locals are referenced relative to a [stack] frame pointer. The local variables from the original context of the function containing the catch would need to accessible, and any additional local variables allocated during the execution of the catch could not be added to the area addressed by the frame pointer because that portion of the stack would contain return addresses and locals for the function throwing the exception, the exception data and any additional functions between the catch function and the throw function.

If is far from impossible to implement, but it would be messy.

IMHO try/catch blocks for this kind of retry logic would have to be very small in scope to be practical and maintainable. Any significant complexity in the scope of the try block (multiple nested functions, etc) is going to create two very tightly coupled sets of code non-obviously separated in the source. This kind of pathological coupling is evil.

Since the scope should be kept small, I would always opt for comprehensive sanity checking before the operation rather than complex, oddly coupled code that is almost impossible to test.