SETJMP(3P)

💖 SETJMP(3P) 💖

okay bestie, welcome to the POSIX Programmer's Manual, section 3P, page SETJMP 🫶 this one's about setjmp() and it's lowkey iconic in a "vintage C sorcery" way, iykyk.

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🌸 PROLOG 🌸

so like, heads up before we get into it: this manual page is part of the POSIX Programmer's Manual, mmkay? the Linux implementation of this interface may differ (so if you're on Linux, go consult the corresponding Linux manual page for the deets on Linux behavior, fr fr), or honestly the interface may not be implemented on Linux at all. no cap.

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✨ NAME ✨

setjmp — set jump point for a non-local goto 💅

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🎀 SYNOPSIS 🎀

#include <setjmp.h>

int setjmp(jmp_buf env);

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🦋 DESCRIPTION 🦋

bestie the first thing you gotta know: the functionality described on this reference page is aligned with the ISO C standard. and if there's any conflict between the requirements described here and the ISO C standard? that's unintentional, oops. this volume of POSIX.1‐2017 defers to the ISO C standard, periodt.

okay so here's the tea ☕: a call to setjmp() shall save the calling environment in its env argument, so that longjmp() can come back and use it later. it's giving "bookmark but for your whole vibe".

ngl there's a fun lil ambiguity here: it is unspecified whether setjmp() is a macro or a function 🙈. and listen — if a macro definition is suppressed in order to access an actual function, or a program defines an external identifier with the name setjmp, the behavior is undefined. so don't do that. please.

also, an application shall ensure that an invocation of setjmp() appears in one of these contexts only:

• The entire controlling expression of a selection or iteration statement
• One operand of a relational or equality operator with the other operand an integral constant expression, with the resulting expression being the entire controlling expression of a selection or iteration statement
• The operand of a unary '!' operator with the resulting expression being the entire controlling expression of a selection or iteration statement
• The entire expression of an expression statement (possibly cast to void)

and if the invocation appears in any other context? yeah. the behavior is undefined 💀. main character energy only in those four spots, got it.

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🌈 RETURN VALUE 🌈

If the return is from a direct invocation, setjmp() shall return 0. If the return is from a call to longjmp(), setjmp() shall return a non-zero value. so like, 0 = we just got here normally, non-zero = we teleported back from somewhere 👑

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💜 ERRORS 💜

No errors are defined. ✨ (yes, really, nothing. the following sections are informative btw.)

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🍓 EXAMPLES 🍓

None. 😭 yeah bestie, they really just left us hanging on this one.

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🧚 APPLICATION USAGE 🧚

In general, sigsetjmp() is more useful in dealing with errors and interrupts encountered in a low-level subroutine of a program. so like, if that's your situation, sigsetjmp() is the moment 💅

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⭐ RATIONALE ⭐

None.

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🌸 FUTURE DIRECTIONS 🌸

None.

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👑 SEE ALSO 👑

• longjmp()
• sigsetjmp()

The Base Definitions volume of POSIX.1‐2017, <setjmp.h>

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💖 COPYRIGHT 💖

okay legal bestie moment, gotta read this one exactly:

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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and that's the whole page, bestie 🫶 this lil slice of the POSIX Programmer's Manual is brought to you by IEEE/The Open Group, 2017 — SETJMP(3P), that's a wrap, slay ✨💅