In this scenario, a COBOL main
program invokes a C subroutine
and an exception occurs in the C subroutine.
Refer to Figure 1 throughout the following
discussion.
Figure 1. Stack contents
when the exception occurs in C
The actions taken follow the three Language Environment condition
handling steps: enablement, condition, and termination imminent.
- In the enablement step, C determines
whether the exception in the C routine should be enabled and treated
as a condition. If any of the following are true, the exception is
ignored, and processing continues at the next sequential instruction
after which the exception occurred:
If you did none of these things, the condition is enabled and
processed as a condition.
- If a user-written condition handler has been registered using
CEEHDLR on the C stack
frame, it is given control. If it issues a resume, with or without
moving the resume cursor, the condition handling step ends. Processing
continues in the routine to which the resume cursor points.
In
this example, there is not a user-written condition handler registered
for the condition, so the condition is percolated.
- The global error table is now examined for signal handlers that
have been registered for the condition.
If there is a signal handler
registered for the condition, it is given control. If it issues a
resume or a call to longjmp(), the condition handling
step ends. Processing resumes in the routine to which the resume cursor
points. You must be careful when issuing a longjmp() in
an application that contains a COBOL program;
see CEEMRCR and COBOL for details.
In
this example no C signal handler is registered for the condition,
so the condition is percolated.
- The condition is still unhandled. If C does
not recognize the condition, or if the C default
action (listed in Table 2)
is to terminate, the condition is percolated.
- If a user-written condition handler has been registered using
CEEHDLR on the COBOL stack
frame, it is given control. If it issues a resume, with or without
moving the resume cursor, the condition handling step ends. Processing
continues in the routine to which the resume cursor points. You must
be careful when moving the resume cursor in an application that contains
a COBOL program;
see CEEMRCR and COBOL for details.
In this
example, no user-written condition handler is registered for the condition,
so the condition is percolated.
- If the condition is of severity 0 or 1, the Language Environment default
actions take place, as described in Table 1.
- If the condition is of severity 2 or above, Language Environment default
action is to promote the condition to T_I_U (Termination Imminent
due to an Unhandled condition) and redrive the stack. Condition handling
now enters the termination imminent step.
- If, on the second pass of the stack, no condition handler moves
the resume cursor and issues a resume, Language Environment terminates
the thread.