NAME
makecontext,
swapcontext —
modify and exchange user thread
contexts
LIBRARY
library “libc”
SYNOPSIS
#include
<ucontext.h>
void
makecontext(ucontext_t *ucp,
void (*func)(void), int argc,
...);
int
swapcontext(ucontext_t
*oucp, const ucontext_t
*ucp);
DESCRIPTION
Themakecontext()
function modifies the user thread context pointed to by
ucp, which must have previously been initialized by a
call to
getcontext(3) and had a stack allocated for it. The context is
modified so that it will continue execution by invoking
func()
with the arguments provided. The argc argument must be
equal to the number of additional arguments provided to
makecontext() and also equal to the number of
arguments to func(), or else the behavior is
undefined.
The ucp->uc_link
argument must be initialized before calling
makecontext()
and determines the action to take when
func()
returns: if equal to NULL, the process exits;
otherwise,
setcontext(ucp->uc_link)
is implicitly invoked.
The
swapcontext()
function saves the current thread context in *oucp and
makes *ucp the currently active context.
RETURN VALUES
If successful, swapcontext() returns zero;
otherwise -1 is returned and the global variable errno
is set appropriately.
ERRORS
The swapcontext() function will fail
if:
- [
ENOMEM] - There is not enough stack space in ucp to complete the operation.