MAKECONTEXT(3) | Library Functions Manual | MAKECONTEXT(3) |
makecontext
, swapcontext
—
#include <ucontext.h>
void
makecontext
(ucontext_t
*ucp, void
(*func)(), int
argc, ...);
int
swapcontext
(ucontext_t
* restrict oucp,
ucontext_t * restrict
ucp);
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).
makecontext
() function returns no value.
On success, swapcontext
() returns a value
of 0, Otherwise, -1 is returned and errno is set to
indicate the error.
swapcontext
() function will fail if:
makecontext
() and
swapcontext
() functions conform to
X/Open System Interfaces and Headers Issue 5
(“XSH5”) and IEEE Std 1003.1-2001
(“POSIX.1”).
The IEEE Std 1003.1-2004
(“POSIX.1”) revision marked the functions
makecontext
() and
swapcontext
() as obsolete, citing portability issues
and recommending the use of POSIX threads instead. The IEEE
Std 1003.1-2008 (“POSIX.1”) revision removed the
functions from the specification.
makecontext
(); portable applications should not rely
on the implementation detail that it may be possible to pass pointer arguments
to functions.makecontext
() and
swapcontext
() functions first appeared in
AT&T System V Release 4 UNIX.
May 4, 2012 | NetBSD 9.0 |