MPE/iX Intrinsics Reference Manual (32650-90875)

Chapter 10 641
Command Definitions (QUIT-ZSIZE)
XSYSTRAP
XSYSTRAP
NM and CM callable (differences noted below).
Enables or disables a user-written system trap handling procedure.
Syntax
I*V I*
XSYSTRAP(
plabel,oldplabel );
NOTE Any user trap handler cannot perform a GOTO out of that procedure.
Performing an ESCAPE (Pascal) or completing the trap handling procedure
are the only valid ways to return. The state of the process and the program
results are not predictable after a non-local GOTO statement.
Parameters
plabel (NM) 32-bit signed integer by value (required)
(CM) 16-bit signed integer by value (required)
Passes the external-type label of the trap handling procedure. If the value
is 0, the trap handler is disabled.
oldplabel (NM) 32-bit signed integer by reference (required)
(CM) 16-bit signed integer by reference (required)
Returns the
plabel of the process's previous software library trap handler.
If no
plabel was previously configured, 0 is returned.
Operation Notes
When a program begins execution, the user-written system trap handler is disabled
automatically. When enabled by the XSYSTRAP intrinsic, and subsequently activated by an
error, the user-written system trap handler assumes control.
The trap handler can be enabled or disabled by calling the XSYSTRAP intrinsic.
Condition Codes
CCE (2) Request granted. Trap enabled.
CCG (0) Request granted. Trap disabled.
CCL (1) Request denied. An illegal
plabel was specified.
Related Information
Manual Trap Handling Programmer's Guide