June 13, 2001 UCONTEXT 2

### NAME

ucontext - user context

### SYNOPSIS

### DESCRIPTION

ucontext_t is a structure type which is used to describe the context of a thread of control within the execution of a process.

ucontext_t includes the following members:

  `

      ucontext_t *  uc_link
      sigset_t      uc_sigmask
      stack_t       uc_stack
      mcontext_t    uc_mcontext

  `

The ```uc_link` member points to the context that will be resumed after the function specified when modifying a context using makecontext(3) has returned. 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 ```uc_sigmask` member is the set of signals that are blocked when the context is activated. Further information can be found in sigprocmask(2).

The ```uc_stack` member defines the stack used by the context. Further information can be found in sigaltstack(2).

The ```uc_mcontext` member defines the machine state associated with the context; it may consist of general registers, floating point registers and other machine-specific information. Its description is beyond the scope of this manual page; portable applications should not access this structure member.

### SEE ALSO

_exit(2), getcontext(2), setcontext(2), sigaltstack(2), sigprocmask(2), makecontext(3), swapcontext(3)

### STANDARDS

The ucontext_t type conforms to X/Open System Interfaces and Headers Issue 5 (``XSH5'') .

### HISTORY

The makecontext(``) and swapcontext(``) functions first appeared in `AT&T` System V.4 `UNIX`.