GETCONTEXT(3) Library Functions Manual GETCONTEXT(3)

getcontext, setcontext — get and set user thread context

Standard C Library (libc, -lc)

#include <ucontext.h>

int
getcontext(ucontext_t *ucp);

int
setcontext(const ucontext_t *ucp);

The () function saves the current thread's execution context in the structure pointed to by ucp. This saved context may then later be restored by calling setcontext().

The () function makes a previously saved thread context the current thread context, i.e., the current context is lost and setcontext() does not return. Instead, execution continues in the context specified by ucp, which must have been previously initialized by a call to getcontext(), makecontext(3), or by being passed as an argument to a signal handler (see sigaction(2)).

If ucp was initialized by (), then execution continues as if the original getcontext() call had just returned (again).

If ucp was initialized by makecontext(3), execution continues with the invocation of the function specified to makecontext(3). When that function returns, ucp->uc_link determines what happens next: if ucp->uc_link is NULL, the process exits; otherwise, (ucp->uc_link) is implicitly invoked.

If ucp was initialized by the invocation of a signal handler, execution continues at the point the thread was interrupted by the signal.

If successful, getcontext() returns zero and setcontext() does not return; otherwise -1 is returned.

No errors are defined for getcontext() or setcontext().

sigaction(2), sigaltstack(2), makecontext(3), ucontext(3)

September 10, 2002 macOS 15.0