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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |ATTRIBUTES |VERSIONS |STANDARDS |HISTORY |EXAMPLES |SEE ALSO |COLOPHON | |
pthread_cleanup_push(3) Library Functions Manualpthread_cleanup_push(3)pthread_cleanup_push, pthread_cleanup_pop - push and pop thread cancelation clean-up handlers
POSIX threads library (libpthread,-lpthread)
#include <pthread.h>void pthread_cleanup_push(typeof(void (void *)) *routine, void *arg);void pthread_cleanup_pop(intexecute);
These functions manipulate the calling thread's stack of thread- cancelation clean-up handlers. A clean-up handler is a function that is automatically executed when a thread is canceled (or in various other circumstances described below); it might, for example, unlock a mutex so that it becomes available to other threads in the process. Thepthread_cleanup_push() function pushesroutine onto the top of the stack of clean-up handlers. Whenroutine is later invoked, it will be givenarg as its argument. Thepthread_cleanup_pop() function removes the routine at the top of the stack of clean-up handlers, and optionally executes it ifexecute is nonzero. A cancelation clean-up handler is popped from the stack and executed in the following circumstances: • When a thread is canceled, all of the stacked clean-up handlers are popped and executed in the reverse of the order in which they were pushed onto the stack. • When a thread terminates by callingpthread_exit(3), all clean- up handlers are executed as described in the preceding point. (Clean-up handlers arenot called if the thread terminates by performing areturn from the thread start function.) • When a thread callspthread_cleanup_pop() with a nonzeroexecute argument, the top-most clean-up handler is popped and executed. POSIX.1 permitspthread_cleanup_push() andpthread_cleanup_pop() to be implemented as macros that expand to text containing '{' and '}', respectively. For this reason, the caller must ensure that calls to these functions are paired within the same function, and at the same lexical nesting level. (In other words, a clean-up handler is established only during the execution of a specified section of code.) Callinglongjmp(3) (siglongjmp(3)) produces undefined results if any call has been made topthread_cleanup_push() orpthread_cleanup_pop() without the matching call of the pair since the jump buffer was filled bysetjmp(3) (sigsetjmp(3)). Likewise, callinglongjmp(3) (siglongjmp(3)) from inside a clean-up handler produces undefined results unless the jump buffer was also filled bysetjmp(3) (sigsetjmp(3)) inside the handler.These functions do not return a value.
There are no errors.
For an explanation of the terms used in this section, seeattributes(7). ┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface│Attribute│Value│ ├──────────────────────────────────────┼───────────────┼─────────┤ │pthread_cleanup_push(), │ Thread safety │ MT-Safe │ │pthread_cleanup_pop() │ │ │ └──────────────────────────────────────┴───────────────┴─────────┘
On glibc, thepthread_cleanup_push() andpthread_cleanup_pop() functionsare implemented as macros that expand to text containing '{' and '}', respectively. This means that variables declared within the scope of paired calls to these functions will be visible within only that scope. POSIX.1 says that the effect of usingreturn,break,continue, orgoto to prematurely leave a block bracketedpthread_cleanup_push() andpthread_cleanup_pop() is undefined. Portable applications should avoid doing this.POSIX.1-2008.
POSIX.1-2001. glibc 2.0.
The program below provides a simple example of the use of the functions described in this page. The program creates a thread that executes a loop bracketed bypthread_cleanup_push() andpthread_cleanup_pop(). This loop increments a global variable,cnt, once each second. Depending on what command-line arguments are supplied, the main thread sends the other thread a cancelation request, or sets a global variable that causes the other thread to exit its loop and terminate normally (by doing areturn). In the following shell session, the main thread sends a cancelation request to the other thread: $./a.out; New thread started cnt = 0 cnt = 1 Canceling thread Called clean-up handler Thread was canceled; cnt = 0 From the above, we see that the thread was canceled, and that the cancelation clean-up handler was called and it reset the value of the global variablecnt to 0. In the next run, the main program sets a global variable that causes other thread to terminate normally: $./a.out x; New thread started cnt = 0 cnt = 1 Thread terminated normally; cnt = 2 From the above, we see that the clean-up handler was not executed (becausecleanup_pop_arg was 0), and therefore the value ofcnt was not reset. In the next run, the main program sets a global variable that causes the other thread to terminate normally, and supplies a nonzero value forcleanup_pop_arg: $./a.out x 1; New thread started cnt = 0 cnt = 1 Called clean-up handler Thread terminated normally; cnt = 0 In the above, we see that although the thread was not canceled, the clean-up handler was executed, because the argument given topthread_cleanup_pop() was nonzero.Program source #include <errno.h> #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <unistd.h> #define handle_error_en(en, msg) \ do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0) static int done = 0; static int cleanup_pop_arg = 0; static int cnt = 0; static void cleanup_handler(void *arg) { printf("Called clean-up handler\n"); cnt = 0; } static void * thread_start(void *arg) { time_t curr; printf("New thread started\n"); pthread_cleanup_push(cleanup_handler, NULL); curr = time(NULL); while (!done) { pthread_testcancel(); /* A cancelation point */ if (curr < time(NULL)) { curr = time(NULL); printf("cnt = %d\n", cnt); /* A cancelation point */ cnt++; } } pthread_cleanup_pop(cleanup_pop_arg); return NULL; } int main(int argc, char *argv[]) { pthread_t thr; int s; void *res; s = pthread_create(&thr, NULL, thread_start, NULL); if (s != 0) handle_error_en(s, "pthread_create"); sleep(2); /* Allow new thread to run a while */ if (argc > 1) { if (argc > 2) cleanup_pop_arg = atoi(argv[2]); done = 1; } else { printf("Canceling thread\n"); s = pthread_cancel(thr); if (s != 0) handle_error_en(s, "pthread_cancel"); } s = pthread_join(thr, &res); if (s != 0) handle_error_en(s, "pthread_join"); if (res == PTHREAD_CANCELED) printf("Thread was canceled; cnt = %d\n", cnt); else printf("Thread terminated normally; cnt = %d\n", cnt); exit(EXIT_SUCCESS); }pthread_cancel(3),pthread_cleanup_push_defer_np(3),pthread_setcancelstate(3),pthread_testcancel(3),pthreads(7)
This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17pthread_cleanup_push(3)Pages that refer to this page:pthread_cancel(3), pthread_cleanup_push_defer_np(3), pthread_exit(3), pthread_setcancelstate(3), pthread_testcancel(3), pthreads(7)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |