1LONGJMP(3P) POSIX Programmer's Manual LONGJMP(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 longjmp — non-local goto
13
15 #include <setjmp.h>
16 void longjmp(jmp_buf env, int val);
18
20 The functionality described on this reference page is aligned with the
21 ISO C standard. Any conflict between the requirements described here
22 and the ISO C standard is unintentional. This volume of POSIX.1‐2017
23 defers to the ISO C standard.
24 The longjmp() function shall restore the environment saved by the most
26 recent invocation of setjmp() in the same process, with the correspond‐
27 ing jmp_buf argument. If the most recent invocation of setjmp() with
28 the corresponding jmp_buf occurred in another thread, or if there is no
29 such invocation, or if the function containing the invocation of
30 setjmp() has terminated execution in the interim, or if the invocation
31 of setjmp() was within the scope of an identifier with variably modi‐
32 fied type and execution has left that scope in the interim, the behav‐
33 ior is undefined. It is unspecified whether longjmp() restores the
34 signal mask, leaves the signal mask unchanged, or restores it to its
35 value at the time setjmp() was called.
36 All accessible objects have values, and all other components of the
38 abstract machine have state (for example, floating-point status flags
39 and open files), as of the time longjmp() was called, except that the
40 values of objects of automatic storage duration are unspecified if they
41 meet all the following conditions:
42 * They are local to the function containing the corresponding
44 setjmp() invocation.
45 * They do not have volatile-qualified type.
47 * They are changed between the setjmp() invocation and longjmp()
49 call.
50 Although longjmp() is an async-signal-safe function, if it is invoked
52 from a signal handler which interrupted a non-async-signal-safe func‐
53 tion or equivalent (such as the processing equivalent to exit() per‐
54 formed after a return from the initial call to main()), the behavior of
55 any subsequent call to a non-async-signal-safe function or equivalent
56 is undefined.
57 The effect of a call to longjmp() where initialization of the jmp_buf
59 structure was not performed in the calling thread is undefined.
60
62 After longjmp() is completed, program execution continues as if the
63 corresponding invocation of setjmp() had just returned the value speci‐
64 fied by val. The longjmp() function shall not cause setjmp() to return
65 0; if val is 0, setjmp() shall return 1.
66
68 No errors are defined.
69 The following sections are informative.
71
73 None.
74
76 Applications whose behavior depends on the value of the signal mask
77 should not use longjmp() and setjmp(), since their effect on the signal
78 mask is unspecified, but should instead use the siglongjmp() and
79 sigsetjmp() functions (which can save and restore the signal mask under
80 application control).
81 It is recommended that applications do not call longjmp() or sig‐
83 longjmp() from signal handlers. To avoid undefined behavior when call‐
84 ing these functions from a signal handler, the application needs to
85 ensure one of the following two things:
86 1. After the call to longjmp() or siglongjmp() the process only calls
88 async-signal-safe functions and does not return from the initial
89 call to main().
90 2. Any signal whose handler calls longjmp() or siglongjmp() is blocked
92 during every call to a non-async-signal-safe function, and no such
93 calls are made after returning from the initial call to main().
94
96 None.
97
99 None.
100
102 setjmp(), sigaction(), siglongjmp(), sigsetjmp()
103 The Base Definitions volume of POSIX.1‐2017, <setjmp.h>
105
107 Portions of this text are reprinted and reproduced in electronic form
108 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
109 table Operating System Interface (POSIX), The Open Group Base Specifi‐
110 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
111 Electrical and Electronics Engineers, Inc and The Open Group. In the
112 event of any discrepancy between this version and the original IEEE and
113 The Open Group Standard, the original IEEE and The Open Group Standard
114 is the referee document. The original Standard can be obtained online
115 at http://www.opengroup.org/unix/online.html .
116 Any typographical or formatting errors that appear in this page are
118 most likely to have been introduced during the conversion of the source
119 files to man page format. To report such errors, see https://www.ker‐
120 nel.org/doc/man-pages/reporting_bugs.html .
121IEEE/The Open Group 2017 LONGJMP(3P)