PTHREAD_EXIT(3POSIX)

💖 PTHREAD_EXIT 💖 — thread termination, but make it a farewell tour

okay bestie, welcome to PTHREAD_EXIT(3POSIX), straight out of the POSIX Programmer's Manual. this is the page about telling a thread "girl, your shift is over 💅".

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🌸 PROLOG 🌸

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux. iykyk — always double check which flavor of Unix you're actually on, bestie.

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✨ NAME ✨

pthread_exit — thread termination. it's the goodbye text of the C world 🫶

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🎀 SYNOPSIS 🎀

#include <pthread.h>

void pthread_exit(void *value_ptr);

like, that's it. one function. no return value. no drama (well, a little drama).

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💅 DESCRIPTION 💅

so here's the tea ☕. The pthread_exit() function shall terminate the calling thread and make the value value_ptr available to any successful join with the terminating thread. so whatever you pass in there? that's the lil gift bag 🎁 the joiner gets to open.

Any cancellation cleanup handlers that have been pushed and not yet popped shall be popped in the reverse order that they were pushed and then executed. yes bestie, reverse order — LIFO, stack vibes, the way nature intended 🧚. After all cancellation cleanup handlers have been executed, if the thread has any thread-specific data, appropriate destructor functions shall be called in an unspecified order — so like, don't go assuming a sequence there, okay? 🙈

⚠️ Thread termination does not release any application visible process resources, including, but not limited to, mutexes and file descriptors, nor does it perform any process-level cleanup actions, including, but not limited to, calling any atexit() routines that may exist.

read that again fr fr. your thread dipped 🏃‍♀️ but the mutex is still locked and the fd is still open. no cap. that's on you to handle.

An implicit call to pthread_exit() is made when a thread other than the thread in which main() was first invoked returns from the start routine that was used to create it. The function's return value shall serve as the thread's exit status. so even if you never type pthread_exit(), it's happening behind the scenes — main character energy behind the curtain 🎭.

💀 The behavior of pthread_exit() is undefined if called from a cancellation cleanup handler or destructor function that was invoked as a result of either an implicit or explicit call to pthread_exit().

do not do this. it's giving chaos. it's giving "please don't".

After a thread has terminated, the result of access to local (auto) variables of the thread is undefined. Thus, references to local variables of the exiting thread should not be used for the pthread_exit() value_ptr parameter value. 🚨 NEVER hand out a pointer to a local variable of a thread that's about to be gone-gone. that's a dangling pointer and it will betray you.

The process shall exit with an exit status of 0 after the last thread has been terminated. The behavior shall be as if the implementation called exit() with a zero argument at thread termination time. last one out turns off the lights 💡⭐

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🌈 RETURN VALUE 🌈

The pthread_exit() function cannot return to its caller. bestie it literally can't. it doesn't come back. it left the group chat. that's the whole point 💀

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💜 ERRORS 💜

No errors are defined. zero. none. it simply does not have a bad day ✨

The following sections are informative.

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🍓 EXAMPLES 🍓

None. (i know, i know, we were all hoping 😭)

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🦋 APPLICATION USAGE 🦋

None.

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👑 RATIONALE 👑

The normal mechanism by which a thread terminates is to return from the routine that was specified in the pthread_create() call that started it. The pthread_exit() function provides the capability for a thread to terminate without requiring a return from the start routine of that thread, thereby providing a function analogous to exit(). so it's the "i'm leaving early, don't wait up" option 🌙

Regardless of the method of thread termination, any cancellation cleanup handlers that have been pushed and not yet popped are executed, and the destructors for any existing thread-specific data are executed. This volume of POSIX.1-2017 requires that cancellation cleanup handlers be popped and called in order. After all cancellation cleanup handlers have been executed, thread-specific data destructors are called, in an unspecified order, for each item of thread-specific data that exists in the thread. This ordering is necessary because cancellation cleanup handlers may rely on thread-specific data. see, it's not random, it's structural — the handlers go first because they might need the TSD 🧠✨

As the meaning of the status is determined by the application (except when the thread has been canceled, in which case it is PTHREAD_CANCELED), the implementation has no idea what an illegal status value is, which is why no address error checking is done. so like... the OS is not your mom here. it does not check your pointer. you are the main character and you are responsible for your own choices 💅

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🌟 FUTURE DIRECTIONS 🌟

None. this page is not going anywhere, periodt.

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💖 SEE ALSO 💖

• exit()
• pthread_create()
• pthread_join()

The Base Definitions volume of POSIX.1-2017, <pthread.h>

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📜 COPYRIGHT 📜

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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okay that's the whole page bestie, no notes, we ate 🍽️✨

IEEE/The Open Group — 2017 — PTHREAD_EXIT(3POSIX)

and that's the sign-off, love u, go clean up your mutexes before you pthread_exit() 🫶💖🎀