Module `Exninfo`

Additional information worn by exceptions.

type 'a t: Information containing a given type.

type info: All information

type iexn = exn * info: Information-wearing exceptions

val make : unit -> 'a t: Create a new piece of information.

val null : info: No information

val add : info -> 'a t -> 'a -> info: Add information to an exception.

val get : info -> 'a t -> 'a option: Get information worn by an exception. Returns None if undefined.

val info : exn -> info: Retrieve the information of the last exception raised.

type backtrace

val get_backtrace : info -> backtrace option: get_backtrace info does get the backtrace associated to info

val backtrace_to_string : backtrace -> string: backtrace_to_string info does get the backtrace associated to info

val record_backtrace : bool -> unit

val capture : exn -> iexn

Add the current backtrace information and other meta-data to the given exception.

The intended use case is to re-raise an exception while preserving the meta-data:

try foo
with
| Bar -> bar
| My_exn _ as exn ->
  let (exn, info) = Exninfo.capture err in
  ...
  let info = ... in
  Exninfo.iraise (exn, info)

| exn when CErrors.noncritical exn ->
  let iexn = Exninfo.capture err in
  ...
  Exninfo.iraise iexn

where baz should re-raise using iraise below.

WARNING: any intermediate code between the with and the handler may modify the backtrace. Yes, that includes when clauses. Ideally, what you should do is something like:

try foo
with exn when CErrors.noncritical exn ->
  let (err, info) = Exninfo.capture exn in
  match err with
  | exception Bar -> ...
  | err -> ...

I admit that's a bit heavy, but there is not much to do...

val iraise : iexn -> 'a: Raise the given enriched exception.

val reify : unit -> info