MPE/iX Intrinsics Reference Manual (32650-90875)

Chapter 10 639
Command Definitions (QUIT-ZSIZE)
XCONTRAP
0:16 16-bit external CM plabel
oldplabel (NM) 32-bit signed integer passed by reference (required)
(CM) 16-bit signed integer passed by reference (required)
Returns the plabel of the process's previous subsystem break trap handler.
It can be either a CM or NM plabel, as described above. If no plabel was
previously configured,
oldplabel returns 0.
Operation Notes
Call XCONTRAP to arm a user-written subsystem break trap handling procedure. This trap
handler is invoked when an enabled subsystem break signal is received during an
interactive session. Calling XCONTRAP from a job results in an error.
On most terminals, transmit the subsystem break signal by pressing
CTRLY (the default
for sending a subsystem break signal). Subsystem break traps are also referred to as
control-Y traps.
Only one process in a session can receive a subsystem break trap at any one time. The
process that called XCONTRAP most recently receives the next subsystem break trap. Once a
process has received a subsystem break trap, it cannot receive another until it calls the
RESETCONTROL intrinsic to reenable the subsystem break trap. Only processes running in a
session can enable subsystem break traps. The trap handler can be any procedure in the
program or in the libraries to which the program is bound. The subsystem break trap
handler has no parameters.
Condition Codes
CCE (2) Request granted. Trap enabled.
CCG (0) Request granted. Trap disabled.
CCL (1) Request denied. An illegal
plabel or XCONTRAP was called from a job.
Related Information
Intrinsics FCONTROL, FDEVICECONTROL, RESETCONTROL
Manual Trap Handling Programmer's Guide