xref: /dragonfly/lib/libc/gen/setjmp.3 (revision cd1c6085) 
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32.\"     @(#)setjmp.3	8.1 (Berkeley) 6/4/93
33.\" $FreeBSD: src/lib/libc/gen/setjmp.3,v 1.5.2.5 2003/03/15 15:11:05 trhodes Exp $
34.\" $DragonFly: src/lib/libc/gen/setjmp.3,v 1.2 2003/06/17 04:26:42 dillon Exp $
35.\"
36.Dd June 4, 1993
37.Dt SETJMP 3
38.Os
39.Sh NAME
40.Nm sigsetjmp ,
41.Nm siglongjmp ,
42.Nm setjmp ,
43.Nm longjmp ,
44.Nm _setjmp ,
45.Nm _longjmp ,
46.Nm longjmperror
47.Nd non-local jumps
48.Sh LIBRARY
49.Lb libc
50.Sh SYNOPSIS
51.In setjmp.h
52.Ft int
53.Fn sigsetjmp "sigjmp_buf env" "int savemask"
54.Ft void
55.Fn siglongjmp "sigjmp_buf env" "int val"
56.Ft int
57.Fn setjmp "jmp_buf env"
58.Ft void
59.Fn longjmp "jmp_buf env" "int val"
60.Ft int
61.Fn _setjmp "jmp_buf env"
62.Ft void
63.Fn _longjmp "jmp_buf env" "int val"
64.Ft void
65.Fn longjmperror void
66.Sh DESCRIPTION
67The
68.Fn sigsetjmp ,
69.Fn setjmp ,
70and
71.Fn _setjmp
72functions save their calling environment in
73.Fa env .
74Each of these functions returns 0.
75.Pp
76The corresponding
77.Fn longjmp
78functions restore the environment saved by their most recent respective
79invocations
80of the
81.Fn setjmp
82function.
83They then return so that program execution continues as if the corresponding
84invocation of the
85.Fn setjmp
86call had just returned  the value specified by
87.Fa val ,
88instead of 0.
89.Pp
90Pairs of calls may be intermixed, i.e. both
91.Fn sigsetjmp
92and
93.Fn siglongjmp
94and
95.Fn setjmp
96and
97.Fn longjmp
98combinations may be used in the same program, however, individual
99calls may not, e.g. the
100.Fa env
101argument to
102.Fn setjmp
103may not be passed to
104.Fn siglongjmp .
105.Pp
106The
107.Fn longjmp
108routines may not be called after the routine which called the
109.Fn setjmp
110routines returns.
111.Pp
112All accessible objects have values as of the time
113.Fn longjmp
114routine was called, except that the values of objects of automatic storage
115invocation duration that do not have the
116.Vt volatile
117type and have been changed between the
118.Fn setjmp
119invocation and
120.Fn longjmp
121call are indeterminate.
122.Pp
123The
124.Fn setjmp Ns / Ns Fn longjmp
125pairs save and restore the signal mask while
126.Fn _setjmp Ns / Ns Fn _longjmp
127pairs save and restore only the register set and the stack.
128(See
129.Fn sigprocmask 2 . )
130.Pp
131The
132.Fn sigsetjmp Ns / Ns Fn siglongjmp
133function
134pairs save and restore the signal mask if the argument
135.Fa savemask
136is non-zero, otherwise only the register set and the stack are saved.
137.Sh ERRORS
138If the contents of the
139.Fa env
140are corrupted, or correspond to an environment that has already returned,
141the
142.Fn longjmp
143routine calls the routine
144.Fn longjmperror 3 .
145If
146.Fn longjmperror
147returns the program is aborted (see
148.Xr abort 3 ) .
149The default version of
150.Fn longjmperror
151prints the message
152.Dq Li longjmp botch
153to standard error and returns.
154User programs wishing to exit more gracefully should write their own
155versions of
156.Fn longjmperror .
157.Sh SEE ALSO
158.Xr sigaction 2 ,
159.Xr sigaltstack 2 ,
160.Xr signal 3
161.Sh STANDARDS
162The
163.Fn setjmp
164and
165.Fn longjmp
166functions conform to
167.St -isoC .
168The
169.Fn sigsetjmp
170and
171.Fn siglongjmp
172functions conform to
173.St -p1003.1-88 .
174