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exc_resume(3)
NAME
  exc_resume, exc_longjmp, exc_capture_context, exc_continue, exc_unwind,
  RtlUnwindRfp - entry points that support resuming execution of user code

SYNOPSIS
  #include <excpt.h>

  void exc_resume(
	  PCONTEXT contextRecord );

  void exc_longjmp(
	  PCONTEXT contextRecord,
	  long returnValue );

  unsigned long exc_capture_context(
	  PCONTEXT contextRecord );

  void exc_continue(
	  PCONTEXT contextRecord );

  void exc_unwind(
	  void TargetFrame,
	  void TargetIp,
	  system_exrec_type *exceptionRecord,
	  long returnValue );

  void RtlUnwindRfp(
	  void *TargetRealFrame,
	  void *TargetIp,
	  system_exrec_type *exceptionRecord,
	  long returnValue );

LIBRARY
  Exception Handling Library (libexc.a)

PARAMETERS
  contextRecord
      Pointer to a struct sigcontext (see signal(2)) used to represent a
      procedure's context.

  returnValue
      Value to be passed to the continuing code at the completion of the
      unwind.

  TargetFrame
      If nonzero, virtual frame pointer of the target procedure invocation to
      which the unwind is to be done; if zero, specifies that an exit unwind
      is to be initiated and causes the EXCEPTION_EXIT_UNWIND flag to be set
      in the exception record.

  TargetIP
      If TargetRealFrame is nonzero, address within the target invocation at
      which to continue execution; otherwise, this parameter is ignored.

  exceptionRecord
      Address of primary exception record.

  TargetRealFrame
      If nonzero, real frame pointer of the target procedure invocation to
      which the unwind is to be done; if zero, specifies that an exit unwind
      is to be initiated and causes the EXCEPTION_EXIT_UNWIND flag to be set
      in the exception record.

DESCRIPTION
  The exc_resume() and exc_continue() functions perform essentially the same
  operation as longjmp(3). The exc_resume() function is a libexc entry point.

  The exc_capture_context() function saves the current procedure context in
  the struct sigcontext identified by contextRecord.

  The exc_longjmp() function restores the context that was saved by a
  previous call to exc_capture_context() and calls exc_unwind(), setting up
  its arguments from information taken from the contextRecord argument. If
  the returnValue argument is 0 (zero), it is set to 1 (one) before the call.

  The exc_unwind() function initiates an unwind of procedure call frames. It
  sets the EXCEPTION_UNWINDING flag in the exception flags of the exception
  record, which describes the machine state at the time of the exc_unwind()
  call. If the TargetFrame argument is zero, then exc_unwind() also sets the
  EXCEPTION_EXIT_UNWIND flag. It then scans the procedure call frames towards
  the base of the call stack to find the target of the unwind operation.

  The RtlUnwindRfp() function is similar to exc_unwind() except that its
  first argument is a real frame pointer instead of a virtual frame pointer.
  Real frame pointers point to the bottom of the statically allocated portion
  of a stack frame. Virtual frame pointers point to the top of the stack
  frame.

  As it encounters each frame, the unwind code determines the program counter
  where control left the corresponding function by looking at exception
  handler information in the run-time function table built by the linker. If
  the respective routine has an exception handler, then the unwind code calls
  it. This handler should perform cleanup code required for that activation.
  Programs written in the C programming language, which supports structured
  exception handling, usually contain a try...finally block that implements a
  termination handler that performs these chores (see c_excpt(4)).  The
  unwind code also calls a handler when it reaches the TargetFrame so that
  any scope-oriented cleanup code or termination handler can execute. In this
  case, it sets the EXCEPTION_TARGET_FRAME flag in the ExceptionFlags field
  of the exception record.

  Once it finds the TargetFrame (if specified) and calls its handler (if
  available), exc_unwind():

    ·  Sets the PC to the TargetIp

    ·  Sets the return value to be the returnValue argument, if the
       returnValue argument is nonzero,

    ·  Sets the return value to be the ExceptionCode of the exception record
       if the returnValue argument is zero

    ·  Calls exc_continue()

RETURN VALUES
  The exc_capture_context() function returns a value of 0 (zero), unless the
  return is from a call to the exc_longjmp() function, in which case
  exc_capture_context() returns the nonzero value specified in the
  returnValue argument to exc_longjmp().

  The exc_longjmp() function cannot return 0 (zero) to the previous context.
  The value 0 is reserved to indicate the actual return from the
  exc_capture_context() function when first called by the program. If the
  exc_longjmp function() is passed a returnValue parameter of 0, execution
  continues as if the corresponding call to the exc_capture_context()
  function had returned a value of 1.

FILES
       /usr/ccs/lib/cmplrs/cc/libexc.a -- exception handling library
       /usr/include/excpt.h -- include file
       /usr/include/pdsc.h -- include file
       /usr/include/signal.h -- include file
       /usr/include/machine/fpu.h -- include file

SEE ALSO
  Functions: exception_intro(3), exception_dispatcher(3),
  exc_lookup_function_entry(3), signal(2), sigaction(2),
  __exc_last_chance(3), ieee(3).

  Files: excpt(4), c_excpt(4), signal(4), pdsc(4).

  Assembly Language Programmer's Guide.

  Calling Standard for Alpha Systems.

Index for Section 3

Alphabetical listing for E

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