Rational Developer for System z
Enterprise PL/I for z/OS, Version 3.8, Migration Guide

Timing differences

PL/I condition handling semantics remain supported under Language Environment; however, the timing of issuing the run-time message for an ERROR condition with respect to the ERROR ON-Unit is different in the following way:

For PL/I conditions whose implicit action includes issuing a message and raising the ERROR condition, the timing of issuing the message is unchanged.

Table 6 shows when the run-time message for an ERROR condition is issued under OS PL/I with respect to the ERROR On-Unit.

Table 6. OS PL/I Version 2 Release 3 ERROR ON-Unit and Message for an ERROR condition
 Condition
    No
ON-Units
ERROR ON-Unit No GOTO
 ERROR ON-Unit
         GOTO
ERROR condition raised1 Message Message prior to ON-unit Message prior to ON-unit
ZERODIVIDE condition raised2 Message Message prior to ON-unit Message prior to ON-unit
Notes:
1
Taking the square root of a negative number, data exception, etc.
2
With no ZERODIVIDE ON-unit; thus, implicit action is taken. Message is printed, ERROR condition is raised.

Table 7 shows when the run-time message for an ERROR condition is issued under Language Environment with respect to the ERROR On-Unit.

Table 7. Language Environment ERROR ON-Unit and Message for an ERROR Condition
 
Condition
     No
ON-units
ERROR ON-unit
     No GOTO
 ERROR ON-unit
       GOTO
ERROR condition raised1 Message Message after ON-unit No message
ZERODIVIDE condition raised2 Message Message prior to ON-unit Message prior to ON-unit
Notes:
1
Taking the square root of a negative number, data exception, etc.
2
With no ZERODIVIDE ON-unit; thus, implicit action is taken. Message is printed, ERROR condition is raised.

The SNAP traceback message produced by ON ERROR SNAP continues to be issued before the ERROR ON-unit receives control. The SNAP traceback message is not identical to the regular ERROR message.


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