As described in the Itanium™ C++ ABI, __cxa_atexit() registers a destructor function to be called by exit() or when a shared library is unloaded. When a shared library is unloaded, any destructor function associated with that shared library, identified by dso_handle, shall be called with the single argument arg, and then that function shall be removed, or marked as complete, from the list of functions to run at exit(). On a call to exit(), any remaining functions registered shall be called with the single argument arg. Destructor functions shall always be called in the reverse order to their registration (i.e. the most recently registered function shall be called first),
The __cxa_atexit() function is used to implement atexit(), as described in ISO POSIX (2003). Calling atexit(func) from the statically linked part of an application shall be equivalent to __cxa_atexit(func, NULL, NULL).
__cxa_atexit() is not in the source standard; it is only in the binary standard.
Note: atexit() is not in the binary standard; it is only in the source standard.