The TPU$SIGNAL routine allows applications and user-written TPU
    routines such as FILEIO to easily signal error messages in order
    for TPU error handlers to perform correctly.

    Format

      TPU$SIGNAL  condition-code

1  –  Returns

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

    Longword condition value. In most cases, the routine returns
    either the same signal passed to it in the condition value
    argument, or the return value of LIB$SIGNAL. If the routine
    fails, it signals TPU$_FAILURE and returns control to the caller.

2  –  Argument

 condition-code

    OpenVMS usage: cond_value
    type:          longword (unsigned)
    access:        read only
    mechanism:     by value
    The condition-code is an unsigned longword that contains the
    condition code to be signaled. In most cases, this argument is a
    TPU message code.

3  –  Description

    TPU$SIGNAL performs the same function as the Run-Time Library
    routine LIB$SIGNAL, but it also processes TPU facility messages
    to allow TPU language ON_ERROR handlers to be called.

    For example, assume that a user-written file input/output routine
    is designed to signal the error TPU$_OPENIN when it fails to
    open a file. Calling the TPU$SIGNAL routine and passing the value
    TPU$_OPENIN allows a case-style TPU ON_ERROR handler to receive
    the error, thus preserving the documented return values for TPU
    built-in procedures such as READ_FILE.

                                   NOTE

       You must call TPU$INITIALIZE before you call the TPU$SIGNAL
       routine.

    If TPU$_QUITTING, TPU$_EXITING, or TPU$_RECOVERFAIL are passed to
    the routine, it calls the Run-Time Library routine LIB$SIGNAL.

    If facility messages other than TPU messages are passed to the
    TPU$SIGNAL routine, it calls the LIB$SIGNAL routine and passes
    the appropriate condition value.