indeterminate local variable reads
Related to #1742 (closed) and as discussed on #1800, there are further uses of
setjmp errors paths that access non-volatile local variables with the expectation that they are preserved across a call to
longjmp. Unfortunately this property is not true.
Rather than trying to audit this and annotate every accessed variable with
volatile, I propose we simply remove this exception-style control flow. I have not yet assessed how hard this is to do.