In script and eval code a finally block that ends normally leaves the completion value of its try or catch block (ECMA-262 5.1 section 12.14), so try { 1; } finally { 2; } completes with 1. A new GetCompletion instruction saves the value when the finally block starts, and SetCompletion sets it back when the block ends normally; a break, continue or throw out of the finally block still replaces it.
A string returned by a host function is charged to the heap, and one that does not fit after a collection ends the run with the heap limit.