pthread_cleanup_push_defer_np, pthread_cleanup_pop_restore_np - push and pop thread cancellation clean-up handlers while saving cancelability type

#include <pthread.h>
void pthread_cleanup_push_defer_np(void (*routine)(void *),
                                   void *arg);
void pthread_cleanup_pop_restore_np(int execute);
Compile and link with -pthread.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
pthread_cleanup_push_defer_np(), pthread_cleanup_pop_defer_np():

These functions are the same as pthread_cleanup_push(3) and pthread_cleanup_pop(3), except for the differences noted on this page.
Like pthread_cleanup_push(3), pthread_cleanup_push_defer_np() pushes routine onto the thread's stack of cancellation clean-up handlers. In addition, it also saves the thread's current cancelability type, and sets the cancelability type to "deferred" (see pthread_setcanceltype(3)); this ensures that cancellation clean-up will occur even if the thread's cancelability type was "asynchronous" before the call.
Like pthread_cleanup_pop(3), pthread_cleanup_pop_restore_np() pops the top-most clean-up handler from the thread's stack of cancellation clean-up handlers. In addition, it restores the thread's cancelability type to its value at the time of the matching pthread_cleanup_push_defer_np().
The caller must ensure that calls to these functions are paired within the same function, and at the same lexical nesting level. Other restrictions apply, as described in pthread_cleanup_push(3).
This sequence of calls:

pthread_cleanup_push_defer_np(routine, arg);

is equivalent to (but shorter and more efficient than):

int oldtype;
pthread_cleanup_push(routine, arg); pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldtype); ... pthread_setcanceltype(oldtype, NULL); pthread_cleanup_pop(execute);

These functions are nonstandard GNU extensions; hence the suffix "_np" (nonportable) in the names.

pthread_cancel(3), pthread_cleanup_push(3), pthread_setcancelstate(3), pthread_testcancel(3), pthreads(7)
2017-09-15 Linux