Implementations that support implementation-defined actions, such as the creation of a file containing a core image, on termination of some processes traditionally provide a bit in the status returned by wait() to indicate that such actions have occurred.

On implementations that support the creation of a file containing a core image on some process terminations, the WCOREDUMP(stat_val) macro indicates whether creation of a core image was attempted. If it returns a non-zero value this does not necessarily mean that the core image was created, only that it was attempted. For example, if the RLIMIT_CORE limit for the process is 0, this prevents creation of the file; WCOREDUMP(stat_val) returning non-zero in this case indicates that the file would have been created if the limit had not been 0.