Guardian Procedure Calls Reference Manual

trapstack-addr
input
INT:value
is an address specifying the local data area for the application process' trap handler. The
trapstack-addr parameter also indicates where the trap number and stack marker at the
time of the trap are passed to the application process.
If trapstack-addr has a value < 0, then trap handling is disabled and any trap results in
the process being stopped with a process deletion (ABEND) message.
Functions
Use the ARMTRAP procedure to perform one of these functions:
• Arm a trap handler (that is, specify a location in the application program where execution
begins if a trap occurs). To do this, set traphandlr-addr to a value greater than 1 specifying
the address of a label at which the trap handler starts and set trapstack-addr to a
nonnegative value specifying the stack address above which its activation record will go.
• Set default handling (that is terminate, but enter the debugger if in a debug session). To do
this, set traphandlr-addr to 1 and set trapstack-addr to zero.
• Set traps to enter the debugger. To do this, set traphandlr-addr to 1 and
trapstack-addr to a value greater than zero. By convention, both parameters are normally
set to 1 in such as call.
• Disarm all trap handling (that is, specify that no part of the application program is to execute
if a trap occurs). To do this, set traphandlr-addr to a nonzero value and set
trapstack-addr to a negative value. By convention, both parameters are normally set to
-1 in such a call.
• Resume the process and rearm the trap handler. This must be done by a call to ARMTRAP
from within a trap handler with traphandlr-addr set to zero (0) and trapstack-addr
set to a nonnegative value specifying the stack address above which its activation record will
go. For details, see Considerations (page 71).
• Resume the process and disarm all trap handling. This must be done by a call to ARMTRAP
from within a trap handler with traphandlr-addr set to zero (0) and trapstack-addr
set to a negative value. For details, see Considerations (page 71).
Trap Handler Activation and Termination
When a trap handler has been armed and a trap subsequently occurs, control passes to the trap
handler at the location specified by traphandlr-addr in the same code segment as the original
call to ARMTRAP. Trap handling is automatically disabled. ‘S' and ‘L' are set to trapstack-addr
plus 6; the seven words starting at trapstack-addr are (relative to the new ‘L' setting):
Reserved'L'[-6]
Space ID at the time of the trap'L'[-5]
Trap number:
Invalid address reference0
Instruction failure1
Arithmetic overflow2
Stack overflow3
Process loop timer timeout4
Call from process with PIN > 2555
Memory manager read error11
70 Guardian Procedure Calls (A-B)