package xapi-backtrace

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Handling exceptions without losing backtraces
Administrivia
Interop with other languages

xapi-backtrace
- Backtrace
  - Interop

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type t

A backtrace from a particular thread.

include Sexplib0.Sexpable.S with type t := t

val t_of_sexp : Sexplib0.Sexp.t -> t

val sexp_of_t : t -> Sexplib0.Sexp.t

val empty : t

An empty backtrace

val to_string_hum : t -> string

Produce a human-readable printable/loggable version of the backtrace.

Handling exceptions without losing backtraces

Whenever a function raises an exception, the backtrace buffer is emptied. Therefore when we are handling an exception, we must stash away a copy of the backtrace buffer if there is any risk of us raising another (or even the same) exception)

val with_backtraces : (unit -> 'a) -> [ `Ok of 'a | `Error of exn * t ]

Allow backtraces to be recorded for this thread. All new threads must be wrapped in this for the backtrace tracking to work. It is acceptable to nest these wrappers; it will not affect the backtrace recording behaviour.

val is_important : exn -> unit

Declare that the backtrace is important for debugging and should be permanently associated with the exception. Call this function in an exception handler where you might need to re-raise the same exception at the end after performing some cleanup, which could clear the current backtrace buffer.

val get : exn -> t

Get a copy of the backtrace associated with exn

val add : exn -> t -> unit

Associate additional backtrace with an exception. This allows you to combine a backtrace from another process with your current backtrace.

val reraise : exn -> exn -> 'a

reraise old new associates the backtrace of old with new and throws new. Use this if you need to 'launder' an exception e.g. you may want to catch Not_found and throw a more descriptive exception instead without losing the backtrace.

val remove : exn -> t

Get a backtrace associated with exn and remove it from the tables. Use this when you want to print/log or otherwise record the final backtrace.

Administrivia

val set_my_name : string -> unit

Every backtrace line will include a name for this process. By default it will be the executable name, but it could also include the process ID and host.

Interop with other languages

This allows backtraces from other languages (e.g. python) to be converted into OCaml-style backtraces.

module Interop : sig ... end