diff options
| -rw-r--r-- | include/version.h | 2 | ||||
| -rw-r--r-- | man/2/exception | 65 |
2 files changed, 48 insertions, 19 deletions
diff --git a/include/version.h b/include/version.h index 9a3859ec..4b7d3b64 100644 --- a/include/version.h +++ b/include/version.h @@ -1 +1 @@ -#define VERSION "Fourth Edition (20090222)" +#define VERSION "Fourth Edition (20090303)" diff --git a/man/2/exception b/man/2/exception index 1ea4f203..343f6ccc 100644 --- a/man/2/exception +++ b/man/2/exception @@ -1,36 +1,65 @@ .TH EXCEPTION 2 .SH NAME -exception \- Exception module +exception \- obtain data about exceptions and set exception-handling modes .SH SYNOPSIS .EX include "exception.m"; exc := load Exception Exception->PATH; +NOTIFYLEADER, PROPAGATE: con iota; + getexc: fn(pid: int): (int, string, string); -setexcnotifyleader: fn(pid: int): int; -setexcpropagate: fn(pid: int): int; +setexcmode: fn(mode: int): int; .EE .SH DESCRIPTION .B Exception -provides exception-related utility routines to read or write to system -device files. +provides functions to fetch data about exceptions in other processes +and change exception-handling modes. +It encapsulates exception-related operations on files in +.IR prog (3). .PP +When a process incurs an exception, the system saves details before processing the exception, +following Limbo's rules. .B Getexc -returns the last exception to be raised on the process with the given process -id. A process id of -1 is taken to mean the current process. The returned -triple gives the pc value, the module and the exception name or 0, nil, nil -if no exception has occurred. +returns a tuple +.BI ( pc,\ module,\ description ) +that describes the most recent exception raised in process +.IR pid . +(A process id of -1 is taken to mean the current process.) +The tuple contains the pc value, the module name, and the exception name. +The value +.B "(0,\ nil,\ nil)" +is returned if no exception has occurred. .PP -.B Setexcnotifyleader -and -.B setexcpropagate -set 'exceptions notifyleader' and 'exceptions propagate' respectively on the given -process. 0 is returned on success, --1 on failure (for instance if the process is not a group leader or does not exist). -See -.I prog (3) -for the actual meaning of these settings. +By default, when a process incurs an exception that is not handled — +no +.B exception +clause matches that exception — +the process is stopped in a `Broken' state for debugging, +and the exception does not propagate further. +.B Setexcmode +changes the way that the system handles exceptions for the current process +and those it later spawns. +A +.I mode +of +.BR NOTIFYLEADER +makes the invoking process the leader of the +current process group for exception handling. +Subsequently, an exception in any process in the current process group +will atomically destroy all processes in the group except the leader, +and the exception will be raised in the leader. +(This works even when the leader itself incurs the exception.) +A +.I mode +of +.B PROPAGATE +instead causes an exception in any process in the group to be raised in +all process in the group, allowing them all to initiate local error recovery +(ie, within each process). .SH SOURCE .B /appl/lib/exception.b +.SH DIAGNOSTICS +Both functions return -1 on error and set the system error string. .SH SEE ALSO .IR prog (3) |