Module Base.Exn

Exceptions.

sexp_of_t uses a global table of sexp converters. To register a converter for a new exception, add [@@deriving sexp] to its definition. If no suitable converter is found, the standard converter in Printexc will be used to generate an atomic S-expression.

type t = exn
val sexp_of_t : t -> Sexp.t
include Pretty_printer.S with type t := t
val pp : Formatter.t -> t -> unit
exception Finally of t * t

Raised when finalization after an exception failed, too. The first exception argument is the one raised by the initial function, the second exception the one raised by the finalizer.

exception Reraised of string * t
val create_s : Sexp.t -> t

create_s sexp returns an exception t such that phys_equal (sexp_of_t t) sexp. This is useful when one wants to create an exception that serves as a message and the particular exn constructor doesn't matter.

val raise_without_backtrace : t -> _

Same as raise, except that the backtrace is not recorded.

val reraise : t -> string -> _
val reraisef : t -> ('a, unit, string, unit -> _) format4 -> 'a

Types with format4 are hard to read, so here's an example.

let foobar str =
  try
    ...
  with exn ->
    Exn.reraisef exn "Foobar is buggy on: %s" str ()
val to_string : t -> string

Human-readable, multi-line.

val to_string_mach : t -> string

Machine format, single-line.

val protectx : f:('a -> 'b) -> 'a -> finally:('a -> unit) -> 'b

Executes f and afterwards executes finally, whether f throws an exception or not.

val protect : f:(unit -> 'a) -> finally:(unit -> unit) -> 'a
val handle_uncaught : exit:bool -> (unit -> unit) -> unit

handle_uncaught ~exit f catches an exception escaping f and prints an error message to stderr. Exits with return code 1 if exit is true, and returns unit otherwise.

Note that since OCaml 4.02.0, you don't need to use this at the entry point of your program, as the OCaml runtime will do better than this function.

val handle_uncaught_and_exit : (unit -> 'a) -> 'a

handle_uncaught_and_exit f returns f (), unless that raises, in which case it prints the exception and exits nonzero.

val reraise_uncaught : string -> (unit -> 'a) -> 'a

Traces exceptions passing through. Useful because in practice, backtraces still don't seem to work.

Example:

let rogue_function () = if Random.bool () then failwith "foo" else 3
let traced_function () = Exn.reraise_uncaught "rogue_function" rogue_function
                           traced_function ();;
: Program died with Reraised("rogue_function", Failure "foo")
val does_raise : (unit -> _) -> bool

does_raise f returns true iff f () raises, which is often useful in unit tests.

val initialize_module : unit -> unit

User code never calls this. It is called in std_kernel.ml as a top-level side effect to change the display of exceptions and install an uncaught-exception printer.