69 lines
2.2 KiB
Groff
69 lines
2.2 KiB
Groff
.TH SETJMP 3 "June 22, 2006"
|
|
.UC 4
|
|
.SH NAME
|
|
setjmp, longjmp, _setjmp, _longjmp, sigsetjmp, siglongjmp \- save and restore execution contexts
|
|
.SH SYNOPSIS
|
|
.nf
|
|
.ft B
|
|
#include <setjmp.h>
|
|
|
|
int setjmp(jmp_buf env);
|
|
void longjmp(jmp_buf env, int val);
|
|
|
|
int _setjmp(jmp_buf env);
|
|
void _longjmp(jmp_buf env, int val);
|
|
|
|
#define _POSIX_SOURCE
|
|
int sigsetjmp(sigjmp_buf env, int savemask);
|
|
void siglongjmp(sigjmp_buf env, int val);
|
|
.SH DESCRIPTION
|
|
These calls provide a way for a process to save an execution context into a
|
|
buffer, and later resume execution from that context, effectively performing
|
|
a non-local jump. The
|
|
.B setjmp
|
|
family of functions store the context into the \fIenv\fP data structure,
|
|
and return the value 0. The
|
|
.B longjmp
|
|
family of functions jump to the context saved in the given \fIenv\fP data
|
|
structure, causing the process to continue as if it returned from the
|
|
corresponding
|
|
.B setjmp
|
|
call again, but this time with the non-zero return value in \fIval\fP.
|
|
.PP
|
|
The difference between the three pairs of setjmp/longjmp functions lies in the
|
|
behaviour with respect to saving/restoring the process signal mask. POSIX does
|
|
not require the process signal mask to be saved and restored during
|
|
.B setjmp
|
|
/
|
|
.B longjmp
|
|
\. However, the current implementation does this in order to agree with OSF/1
|
|
and other BSD derived systems.
|
|
.PP
|
|
The pair of functions
|
|
.B _setjmp
|
|
/
|
|
.B _longjmp
|
|
, traditional in BSD systems, may be used when the signal mask is not to be
|
|
saved/restored.
|
|
.PP
|
|
Finally, the POSIX
|
|
.B sigsetjmp
|
|
/
|
|
.B siglongjmp
|
|
functions allow the programmer to specify explicitly whether the signal mask
|
|
is to be saved/restored, by means of the \fIsavemask\fP parameter. If this
|
|
parameter is zero, the signal mask will not be saved/restored, otherwise it
|
|
will.
|
|
.SH NOTES
|
|
After the function calling
|
|
.B setjmp
|
|
has returned, the saved context may not be used in a call to
|
|
.B longjmp
|
|
anymore, since the relevant portion of the stack may already have been wiped
|
|
out at that point.
|
|
.PP
|
|
Using these functions to return to a previous state from a signal handler
|
|
is possible but should be done with extreme care, as some interrupted library
|
|
routines may not be reentrant and/or temporarily allocate resources.
|
|
.PP
|
|
See the setjmp.h header file for more implementation details specific to Minix.
|