C atexit() considerations

In all C applications, the atexit list is honored only after all condition handling activity has taken place and all user code is removed from the stack, which invalidates any jump buffer previously established.

With C, you can register a number of routines that gain control during the termination of an enclave. When using the C atexit() function, consider the following:
  • A C atexit routine can nominate only C routines, but those routines can call routines written in other languages.
  • User-written condition handlers can be registered while running an atexit routine. However, any jump buffers established are invalid.
  • If a severity 2 or greater condition arises while running an atexit routine and it is unhandled, further atexit routines are skipped and the Language Environment environment is terminated.
  • A C exit() function or PL/I STOP or EXIT statement issued within an atexit routine halts all other atexit functions.
  • If, while running an atexit routine, an attempt to register another atexit routine is made, the registration is ignored. The atexit routine returns a nonzero result indicating a failure to register the routine.

C++ supports atexit(), but any function pointer input to atexit() must be declared as having extern "C" linkage.

Parent topic: Controlling condition handling in C