NAME
makecontext,
swapcontext —
modify and exchange user thread
contexts
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include
<ucontext.h>
void
makecontext(ucontext_t *ucp,
void (*func)(), int argc,
...);
int
swapcontext(ucontext_t
*oucp, const ucontext_t
*ucp);
DESCRIPTION
The
makecontext()
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 (of type int) 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.