Condition step

The condition step begins after the enablement step has completed and Language Environment determines that an exception in your application should be handled as a condition. In the simplest form of this step, Language Environment traverses the stack beginning with the stack frame for the routine in which the condition occurred and progresses towards earlier stack frames. Throughout the following discussion, refer to Figure 1.

Figure 1. Condition processing

Language Environment condition handling begins at the most recently activated stack frame. This is the stack frame associated with the routine that incurred the condition. In Figure 1, this is A, or routine 4.
Language Environment traverses the stack, stack frame by stack frame, towards earlier stack frames. This is in the direction of arrow B in Figure 1. C/C++ signal handlers or C++ catch clauses can all respond by percolating or handling the condition (see Responses to conditions for a discussion of these actions).
Condition handling is complete if one of the handlers requests the application to resume execution. If all stack frames have been visited, and no condition handler has requested a resume, the language of the routine in which the exception occurred can enforce default condition handling semantics.
Language Environment default actions are then taken based on the severity of the unhandled condition, as indicated in Table 1.

Table 1. Language Environment default responses to unhandled conditions. Language Environment's default responses to unhandled conditions fall into one of two types, depending on whether the condition was signaled using CEESGL and an fc parameter, or the condition came from any other source.
Severity of condition	Condition came from any other source
0 (Informative message)	Resume without issuing message.
1 (Warning Message)	Resume without issuing message.
2 (Program terminated in error)	Terminate the thread. Message issued if TERMTHDACT(MSG) is specified.
3 (Program terminated in severe error)	Terminate the thread. Message issued if TERMTHDACT(MSG) is specified.
4 (Program terminated in critical error)	Terminate the thread. Message issued if TERMTHDACT(MSG) is specified.