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makecontext(2)
NAME
  makecontext, swapcontext - Manipulate user level context switching

SYNOPSIS
  #include  <ucontext.h>

  void	makecontext(
	  ucontext_t *ucp,
	  void (*func)(),
	  int argc ... );

  int swapcontext(
	  ucontext_t *oucp,
	  const ucontext_t *ucp );

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  makecontext(), swapcontext():	 XSH5.0

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  ucp Provides a pointer to a ucontext structure, defined in the <ucontext.h>
      header file.  The ucontext structure contains the signal mask,
      execution stack, and machine registers. (See ucontext(5) for more
      information about the format of the ucontext structure.)

  func
      Specifies a function to be called when program execution begins in the
      new context.

  argc
      Specifies the number of parameters passed to the func() function. You
      include the parameters themselves following the argc parameter.

  oucp
      Pointer to the ucontext structure that holds the current context
      structure.

DESCRIPTION
  The makecontext() function modifies the context specified by the ucp
  parameter.  Before you call the makecontext() function, call the
  getcontext() function to initialize the ucp parameter.

  Before you call the makecontext() function, you should allocate a stack for
  the new context. Also, you should initialize the uc_link member of the
  ucontext structure.  This member determines the context that is resumed
  when the context modified by makecontext() returns. You initialize the
  uc_link member by calling the getcontext() function.

  To execute the new context, call the setcontext() or swapcontext()
  function. Program execution begins by calling the function specified in the
  func parameter.  Any parameters you specify following the argc parameter
  are passed to the func() function.

  The swapcontext() function switches between two user contexts. The function
  stores the current context in the oucp parameter. It then switches
  execution to the context described by the ucp parameter.  When the new
  context finishes execution, control returns to the context described by the
  oucp parameter.

RETURN VALUES
  The makecontext() function does not return.

  On success, the swapcontext() function returns 0 (zero). On failure the
  swapcontext() function returns a value of -1 and sets errno to indicate the
  error.

ERRORS
  The makecontext() or swapcontext() functions set errno to the specified
  values for the following conditions:

  [ENOMEM]
      The ucp parameter has too little stack left to complete the operation.

SEE ALSO
  Functions:  exit(2), getcontext(2), sigaction(2), sigprocmask(2)

  Files:  ucontext(5)

  Standards:  standards(5)

Index for Section 2

Alphabetical listing for M

Top of page