getcontext, setcontext - get or set the user context
SYNOPSIS
#include <ucontext.h>
int getcontext(ucontext_t *ucp);
int setcontext(const ucontext_t *ucp);
where:
ucp points to a structure defined in <ucontext.h> con
taining the signal mask, execution stack, and
machine registers.
DESCRIPTION
getcontext(2) gets the current context of the calling pro
cess, storing it in the ucontext struct pointed to by ucp.
setcontext(2) sets the context of the calling process to
the state stored in the ucontext struct pointed to by ucp.
The struct must either have been created by getcontext(2)
or have been passed as the third parameter of the sigac
tion(2) signal handler.
The ucontext struct created by getcontext(2) is defined in
<ucontext.h> as follows:
typedef struct ucontext
{
unsigned long int uc_flags;
struct ucontext *uc_link;
stack_t uc_stack;
mcontext_t uc_mcontext;
__sigset_t uc_sigmask;
struct _fpstate __fpregs_mem;
} ucontext_t;
RETURN VALUES
getcontext(2) returns 0 on success and -1 on failure.
setcontext(2) does not return a value on success and
returns -1 on failure.
STANDARDS
These functions comform to: XPG4-UNIX.
NOTES
When a signal handler executes, the current user context
is saved and a new context is created by the kernel. If
the calling process leaves the signal handler using
longjmp(2), the original context cannot be restored, and
the result of future calls to getcontext(2) are unpre
dictable. To avoid this problem, use siglongjmp(2) or set
context(2) in signal handlers instead of longjmp(2).
sigaction(2), sigaltstack(2), sigprocmask(2),
sigsetjmp(3), setjmp(3).
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