| Op Code (Hex) | Operand 1 | |||
|---|---|---|---|---|
| 02A1 | Return point |
Operand 1: Signed binary(2) scalar or null.
Description: The instruction terminates execution of the invocation in which the instruction is specified. The automatic storage frame is deallocated.
A Return External instruction can be specified within an invocation's subinvocation, and no exception is signaled.
If a higher invocation exists in the invocation hierarchy, the instruction causes execution to resume in the preceding invocation in the thread hierarchy at an instruction location indirectly specified by operand 1. If operand 1 is binary 0 or null, the next instruction following the Call External instruction from which control was relinquished in the preceding invocation in the hierarchy is given execution control. If the value of operand 1 is not 0, the value represents an index into the instruction definition list (IDL) specified as the return list operand in the Call External instruction, and the value causes control to be passed to the instruction referenced by the corresponding IDL entry. The first IDL entry is referenced by a value of one. If operand 1 is not 0 and no return list was specified in the Call External instruction, or if the value of operand 1 exceeds the number of entries in the IDL, or if the value is negative, a return point invalid (hex 2C02) exception is signaled.
In the initial thread of a process, if a higher invocation does not exist, the Return External instruction causes termination of the current process state. If operand 1 is not 0 and is not null, the return point invalid (hex 2C02) exception is signaled.
If the returning invocation has received control to process an event, then control is returned to the point where the event handler was invoked. In this case, if operand 1 is not 0 and is not null, then a return point invalid (hex 2C02) exception is signaled.
If the returning invocation has received control from the machine to process an exception, the return instruction invalid (hex 2C01) exception is signaled.
If the returning invocation has an activation, the invocation count in the activation is decremented by 1.
If the returning invocation currently has an invocation exit set, the invocation exit is not given control and is implicitly cleared.
06 Addressing
08 Argument/Parameter
10 Damage Encountered
1C Machine-Dependent
20 Machine Support
22 Object Access
24 Pointer Specification
2C Program Execution
2E Resource Control Limit
36 Space Management
44 Protection Violation