## `printexc`: a catch-all exception handler

    value f: ('a -> 'b) -> 'a -> 'b

  `printexc__f fn x` applies `fn` to `x` and returns the result. If the evaluation of `fn x` raises any exception, the name of the exception is printed on standard error output, and the programs aborts with exit code 2. Typical use is `printexc__f main ()`, where `main`, with type `unit->unit`, is the entry point of a standalone program, to catch and print stray exceptions. For `printexc__f` to work properly, the program must have been linked with the `-g` option.