HP-UX Reference (11i v3 07/02) - 2 System Calls (vol 5)

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getcontext(2) getcontext(2)

(DEPRECATED)

NAME

getcontext(), setcontext() - get and set current user context; DEPRECATED

SYNOPSIS

#include <ucontext.h>

int getcontext(ucontext_t *ucp);

int setcontext(const ucontext_t *ucp);

Remarks

getcontext() and setcontext() are deprecated. See the WARNINGS section.

DESCRIPTION

The

getcontext() function initializes the structure pointed to by ucp to the current user context of the

calling process. The ucontext_t type that ucp points to deﬁnes the user context and includes the contents of

the calling process’ machine registers, the signal mask, and the current execution stack.

The

setcontext() function restores the user context pointed to by ucp. A successful call to

setcon-

text()

does not return; program execution resumes at the point speciﬁed by the ucp argument passed to

setcontext() . The ucp argument should be created either by a prior call to getcontext() ,orby

being passed as an argument to a signal handler. If the ucp argument was created with

getcontext()

program execution continues as if the corresponding call of

getcontext() had just returned. If the ucp

argument was created with

makecontext()

, program execution continues with the function passed to

makecontext(). When that function returns, the process continues as if after a call to

setcon-

text()

with the ucp argument that was input to makecontext()

. If the ucp argument was passed to

a signal handler, program execution continues with the program instruction following the instruction inter-

rupted by the signal. If the uc_link member of the

ucontext_t structure pointed to by the ucp argument

is equal to 0, then this context is the main context, and the process will exit when this context returns. The

effects of passing a ucp argument obtained from any other source are unspeciﬁed.

RETURN VALUE

On successful completion,

setcontext() does not return and getcontext() returns 0. Otherwise, a

value of −1 is returned.

WARNINGS

getcontext() and setcontext() are deprecated and should be used only by legacy applications.

Context APIs are not recommended due to possible compatibility problems from release to release, because

context APIs are very architecture-speciﬁc. The context APIs "expose" the architecture to the application,

such that the application may not be compatible with all releases.

If you must use context APIs, be aware of the following:

• Do not copy the context yourself. It is not contiguous. The context may have pointers that may point

back to the original context rather than in the copied context; hence, it will be broken.

• The size of the context will vary in length from release to release.

ERRORS

No errors are deﬁned.

APPLICATION USAGE

When a signal handler is executed, the current user context is saved and a new context is created. If the

process leaves the signal handler via

longjmp(), then it is unspeciﬁed whether the context at the time of

the corresponding setjmp() call is restored and thus whether future calls to getcontext() will pro-

vide an accurate representation of the current context, since the context restored by longjmp() may not

contain all the information that setcontext() requires. Signal handlers should use siglongjmp()

or setcontext() instead.

Portable applications should not modify or access the uc_mcontext member of ucontext_t. A portable appli-

cation cannot assume that context includes any process-wide static data, possibly including errno. Users

manipulating contexts should take care to handle these explicitly when required.