The
makecontext() function modifies the object pointed to by
ucp, which has been initialized using
getcontext(2). When this context is resumed using
swapcontext() or
setcontext(2), program execution continues as if
func had been called with the arguments specified after
argc in the call of
makecontext(). The value of
argc must be equal to the number of integer arguments following it, and must be equal to the number of integer arguments expected by
func; otherwise, the behavior is undefined.
Before being modified using
makecontext(), a stack must be allocated for the context (in the
uc_stack member), and a context to resume after
func has returned must be determined (pointed to by the
uc_link member); otherwise, the behavior is undefined. If
uc_link is a null pointer, then the context is the main context, and the process will exit with an exit status of 0 upon return.
The
swapcontext() function saves the current context in the object pointed to by
oucp, sets the current context to that specified in the object pointed to by
ucp, and resumes execution. When a context saved by
swapcontext() is restored using
setcontext(2), execution will resume as if the corresponding invocation of
swapcontext() had just returned (successfully).