(Alpha and I64 only.) The Get Invocation Handle routine gets an
    invocation handle of any active procedure.

    A thread can obtain an invocation handle corresponding to any
    invocation context block by using the following function format.

    Format

      LIB$GET_INVO_HANDLE  invo_context

1  –  Returns

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

    Invocation handle of the invocation context that was passed.
    If the returned value is LIB$K_INVO_HANDLE_NULL, the invocation
    context that was passed was invalid.

2  –  Argument

 invo_context

    OpenVMS usage:invo_context_blk
    type:         structure
    access:       read only
    mechanism:    by reference

    Address of an invocation context block. Here, only the frame
    pointer and stack pointer fields of an invocation context block
    must be defined.