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siglongjmp
Restore an environment previously saved by sigsetjmp().
Syntax
#include <setjmp.h>
void siglongjmp (sigjmp_buf env, int val);
Parameters
env Passes information needed to restore a previous
environment. This variable was used in a previous call to
sigsetjmp() to save the environment. The type sigjmp_buf
(defined in <setjmp.h>) defines an array of unsigned
integers. For this reason, the env argument does not
require an & operator..
val Passes a value to be returned by sigsetjmp(). If a zero is
passed in this argument, it is changed to a value of 1 to
ensure that siglongjmp() never causes sigsetjmp() to return
a zero value.
Return Values
None.
Description
The siglongjmp() function restores the environment saved in env by a
previous call to the sigsetjmp() macro. If the env argument was
initialized by a call to sigsetjmp() with a non-zero value passed in the
savemask argument, the saved signal mask is also restored by
siglongjmp(). If the env argument was not initialized by a call to
sigsetjmp(), the operation of siglongjmp() is undefined.
After siglongjmp() is completed, the program executes as if the call to
sigsetjmp() (which stored information into the env argument) had returned
a second time. In this case, sigsetjmp() returns either the non-zero
value passed in the val argument of siglongjmp() or 1 if zero was passed
in val.
The restoration of the environment includes trimming the stack so that
all stack frames beyond the frame marked by env are removed. The
siglongjmp() function cannot add stack frames. This means that if a
sequence of functions is:
A == calls ==> B == calls ==> C
and sigsetjmp() is used in function C to save an environment in a global
env, functions B or A may not contain any siglongjmp() calls that
reference the env values. Only subordinate functions may issue calls to
siglongjmp(). As a special case, a function may issue a siglongjmp()
call that references a sigsetjmp() within itself, although this is not
usually done.
The values of objects of automatic storage duration that are not
qualified by volatile are indeterminate if they have changed since the
call to sigsetjmp().
The siglongjmp() function will work correctly in the context of signals
and interrupts and any of their associated functions. However, if the
siglongjmp() function is invoked from a nested signal handler, the
operation of siglongjmp() is undefined.
See Also
sigsetjmp(), POSIX 1003.1 Section 8.3.1