Availability:built-in
[ISO]halt(+Status)Terminate Prolog execution with Status. When possible, raise
the exeption unwind(halt(Status)). Currently,
this is used when halt/1
is called in the main thread and there is no intermediate C
function on the stack that called PL_next_solution()
without the PL_Q_PASS_EXCEPTION flag. Future versions may
also use signal based exit from threads.
After the exception bubbled up to the top or if the halt exeption
could not be raised, system termination starts. System termination (see
also
PL_halt())
preforms the following steps:
- Set the Prolog flag exit_status
to Status.
- Call all hooks registered using at_halt/1.
If Status equals 0 (zero), any of these hooks calls cancel_halt/1,
termination is cancelled.
- Call all hooks registered using PL_at_halt(). In the future,
if any of these hooks returns non-zero, termination will be cancelled.
Currently, this only prints a warning.
- Perform the following system cleanup actions:
- Raise
unwind(halt(Status)) in all running
threads.
- Wait for a maximum of 1 second for all threads to respond to this
exception. Registered thread_at_exit/1
hooks are executed. Threads not responding within 1 second are cancelled
forcefully.
- Flush I/O and close all streams except for standard I/O.
- Reset the terminal if its properties were changed.
- Remove temporary files and incomplete compilation output.
- Reclaim memory.
- Call exit(Status) to terminate the process
halt/1
has been extended in SWI-Prolog to accept the arg abort.
This performs as halt/1
above except that:
- Termination cannot be cancelled with cancel_halt/1.
- abort() is called instead of exit(Status).
In addition to an integer status name we also allow passing a
signal name. This is similar to abort, blocking
halt cancellation and set the termination code to 128+signum. For
example, using halt(term) the system exits with status 143
(= 128+15) on Linux.