CentOS 7.0 - man page for printexc (centos section 3)
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Printexc(3) OCaml library Printexc(3)
Printexc - Facilities for printing exceptions.
: sig end
Facilities for printing exceptions.
val to_string : exn -> string
Printexc.to_string e returns a string representation of the exception e .
val print : ('a -> 'b) -> 'a -> 'b
Printexc.print 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 exception is raised again. The typical use is to catch and report exceptions that
escape a function application.
val catch : ('a -> 'b) -> 'a -> 'b
Printexc.catch fn x is similar to Printexc.print , but aborts the program with exit code 2
after printing the uncaught exception. This function is deprecated: the runtime system is
now able to print uncaught exceptions as precisely as Printexc.catch does. Moreover,
calling Printexc.catch makes it harder to track the location of the exception using the
debugger or the stack backtrace facility. So, do not use Printexc.catch in new code.
val print_backtrace : Pervasives.out_channel -> unit
Printexc.print_backtrace oc prints an exception backtrace on the output channel oc . The
backtrace lists the program locations where the most-recently raised exception was raised
and where it was propagated through function calls.
val get_backtrace : unit -> string
Printexc.get_backtrace () returns a string containing the same exception backtrace that
Printexc.print_backtrace would print.
val record_backtrace : bool -> unit
Printexc.record_backtrace b turns recording of exception backtraces on (if b = true ) or
off (if b = false ). Initially, backtraces are not recorded, unless the b flag is given
to the program through the OCAMLRUNPARAM variable.
val backtrace_status : unit -> bool
Printexc.backtrace_status() returns true if exception backtraces are currently recorded,
false if not.
val register_printer : (exn -> string option) -> unit
Printexc.register_printer fn registers fn as an exception printer. The printer should
return None or raise an exception if it does not know how to convert the passed exception,
and Some s with s the resulting string if it can convert the passed exception. Exceptions
raised by the printer are ignored.
When converting an exception into a string, the printers will be invoked in the reverse
order of their registrations, until a printer returns a Some s value (if no such printer
exists, the runtime will use a generic printer).
When using this mechanism, one should be aware that an exception backtrace is attached to
the thread that saw it raised, rather than to the exception itself. Practically, it means
that the code related to fn should not use the backtrace if it has itself raised an excep-
OCamldoc 2014-06-09 Printexc(3)
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