NAME¶
Printexc - Facilities for printing exceptions and inspecting current call stack.
Module¶
Module Printexc
Documentation¶
Module
Printexc
:
sig end
Facilities for printing exceptions and inspecting current call stack.
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.
Since 3.11.0
val get_backtrace :
unit -> string
Printexc.get_backtrace () returns a string containing the same exception
backtrace that
Printexc.print_backtrace would print.
Since 3.11.0
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.
Since 3.11.0
val backtrace_status :
unit -> bool
Printexc.backtrace_status() returns
true if exception backtraces
are currently recorded,
false if not.
Since 3.11.0
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 exception before.
Since 3.11.2
=== Raw backtraces ===
type raw_backtrace
=== The abstract type backtrace stores exception backtraces in a
low-level format, instead of directly exposing them as string as the
get_backtrace() function does. This allows delaying the formatting of
backtraces to when they are actually printed, which might be useful if
you record more backtraces than you print. ===
val get_raw_backtrace :
unit -> raw_backtrace
val print_raw_backtrace :
Pervasives.out_channel -> raw_backtrace
-> unit
val raw_backtrace_to_string :
raw_backtrace -> string
=== Current call stack ===
val get_callstack :
int -> raw_backtrace
=== Printexc.get_callstack n returns a description of the top of the
call stack on the current program point (for the current thread),
with at most n entries. (Note: this function is not related to
exceptions at all, despite being part of the Printexc module.) ===