module Printexc: BatPrintexc
val pass : ('a -> 'b) -> 'a -> 'b
Printexc.pass 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. This function is a
renamed version of Printexc.print
from stdlib.
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 to_string : exn -> string
Printexc.to_string e
returns a string representation of the
exception e
.
val print_backtrace : 'a BatInnerIO.output -> unit
print_backtrace oc
Prints the 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
with
ss
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).
val print : 'a BatInnerIO.output -> exn -> unit
Print an exception. The stdlib print
function is now named !pass
.
val raise_with_backtrace : exn -> Stdlib.Printexc.raw_backtrace -> 'a
Reraise the exception using the given raw_backtrace for the origin of the exception
typeraw_backtrace =
Stdlib.Printexc.raw_backtrace
The abstract type raw_backtrace
stores a backtrace 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 may be useful if you record more backtraces than you print.
Raw backtraces cannot be marshalled. If you need marshalling, you
should use the array returned by the backtrace_slots
function of
the next section.
val get_raw_backtrace : unit -> raw_backtrace
Printexc.get_raw_backtrace ()
returns the same exception
backtrace that Printexc.print_backtrace
would print, but in
a raw format.
val print_raw_backtrace : Stdlib.out_channel -> raw_backtrace -> unit
Print a raw backtrace in the same format
Printexc.print_backtrace
uses.
val raw_backtrace_to_string : raw_backtrace -> string
Return a string from a raw backtrace, in the same format
Printexc.get_backtrace
uses.
val get_callstack : int -> raw_backtrace
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.)
val default_uncaught_exception_handler : exn -> raw_backtrace -> unit
Printexc.default_uncaught_exception_handler
prints the exception and
backtrace on standard error output.
val set_uncaught_exception_handler : (exn -> raw_backtrace -> unit) -> unit
Printexc.set_uncaught_exception_handler fn
registers fn
as the handler
for uncaught exceptions. The default handler prints the exception and
backtrace on standard error output.
Note that when fn
is called all the functions registered with
Pervasives.at_exit
have already been called. Because of this you must
make sure any output channel fn
writes on is flushed.
If fn
raises an exception, it is ignored.
Those function allow to traverse the slots of a raw backtrace, extract information from them in a programmer-friendly format.
typebacktrace_slot =
Stdlib.Printexc.backtrace_slot
The abstract type backtrace_slot
represents a single slot of
a backtrace.
val backtrace_slots : raw_backtrace -> backtrace_slot array option
Returns the slots of a raw backtrace, or None
if none of them
contain useful information.
In the return array, the slot at index 0
corresponds to the most
recent function call, raise, or primitive get_backtrace
call in
the trace.
Some possible reasons for returning None
are as follow:
-g
)ocamlc -g
)typelocation =
Stdlib.Printexc.location
= {
|
filename : |
|
line_number : |
|
start_char : |
|
end_char : |
}
The type of location information found in backtraces. start_char
and end_char
are positions relative to the beginning of the
line.
module Slot:sig
..end
typeraw_backtrace_slot =
Stdlib.Printexc.raw_backtrace_slot
This type allows direct access to raw backtrace slots, without any conversion in an OCaml-usable data-structure. Being process-specific, they must absolutely not be marshalled, and are unsafe to use for this reason (marshalling them may not fail, but un-marshalling and using the result will result in undefined behavior).
Elements of this type can still be compared and hashed: when two elements are equal, then they represent the same source location (the converse is not necessarily true in presence of inlining, for example).
val raw_backtrace_length : raw_backtrace -> int
raw_backtrace_length bckt
returns the number of slots in the
backtrace bckt
.
val get_raw_backtrace_slot : raw_backtrace -> int -> raw_backtrace_slot
get_raw_backtrace_slot bckt pos
returns the slot in position pos
in the
backtrace bckt
.
val convert_raw_backtrace_slot : raw_backtrace_slot -> backtrace_slot
Extracts the user-friendly backtrace_slot
from a low-level
raw_backtrace_slot
.
val get_raw_backtrace_next_slot : raw_backtrace_slot -> raw_backtrace_slot option
get_raw_backtrace_next_slot slot
returns the next slot inlined, if any.
val exn_slot_id : exn -> int
Printexc.exn_slot_id
returns an integer which uniquely identifies
the constructor used to create the exception value exn
(in the current runtime).
val exn_slot_name : exn -> string
Printexc.exn_slot_name exn
returns the internal name of the constructor
used to create the exception value exn
.
typet =
exn
= ..
The type of exception values.
val use_printers : exn -> string option
Printexc.use_printers e
returns None
if there are no registered
printers and Some s
with else as the resulting string otherwise.
val to_string_default : exn -> string
Printexc.to_string_default e
returns a string representation of the
exception e
, ignoring all registered exception printers.