Description |
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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
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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.
