This test case is motivated by the fact that on OS X, external functions may
cause stack walks into the OCaml-generated stack frames. In particular, the
Objective-C runtime does so in function objc_addExceptionHandler. This function
is invoked from Cocoa. Errors in the stack unwinding info generated by OCaml
can cause random crashes. This test case checks that, for at least one OCaml
program, correct unwind info is generated such that the platform's unwinder
(called libunwind) correctly walks the stack up to the main function. OCaml
used to generate incorrect stack unwinding information for this program. See
PR#7118, PR#7120.
