! *** PREDECLARED TYPES
     
      %IF %DECLARED ( %BASIC$QUADWORD_DECLARED ) = 0 %THEN
         RECORD BASIC$QUADWORD
            LONG FILL ( 2 )
         END RECORD
         %LET %BASIC$QUADWORD_DECLARED = 1
      %END %IF
     
      %IF %DECLARED ( %BASIC$OCTAWORD_DECLARED ) = 0 %THEN
         RECORD BASIC$OCTAWORD
            LONG FILL ( 4 )
         END RECORD
         %LET %BASIC$OCTAWORD_DECLARED = 1
      %END %IF
     
      %IF %DECLARED ( %BASIC$HFLOAT_AXP_DECLARED ) = 0 %THEN
         RECORD BASIC$HFLOAT_AXP
            LONG FILL ( 4 )
         END RECORD
         %LET %BASIC$HFLOAT_AXP_DECLARED = 1
      %END %IF
     
      %IF %DECLARED ( %BASIC$F_FLOATING_COMPLEX_DECL ) = 0 %THEN
         RECORD BASIC$F_FLOATING_COMPLEX
            SINGLE REAL_PART
            SINGLE IMAGINARY_PART
         END RECORD
         %LET %BASIC$F_FLOATING_COMPLEX_DECL = 1
      %END %IF
     
      %IF %DECLARED ( %BASIC$D_FLOATING_COMPLEX_DECL ) = 0 %THEN
         RECORD BASIC$D_FLOATING_COMPLEX
            DOUBLE REAL_PART
            DOUBLE IMAGINARY_PART
         END RECORD
         %LET %BASIC$D_FLOATING_COMPLEX_DECL = 1
      %END %IF
     
      %IF %DECLARED ( %BASIC$G_FLOATING_COMPLEX_DECL ) = 0 %THEN
         RECORD BASIC$G_FLOATING_COMPLEX
            GFLOAT REAL_PART
            GFLOAT IMAGINARY_PART
         END RECORD
         %LET %BASIC$G_FLOATING_COMPLEX_DECL = 1
      %END %IF
     
      %IF %DECLARED ( %BASIC$H_FLOAT_AXP_CMPLX_DCL ) = 0 %THEN
         RECORD BASIC$H_FLOATING_COMPLEX_AXP
            BASIC$HFLOAT_AXP REAL_PART
            BASIC$HFLOAT_AXP IMAGINARY_PART
         END RECORD
         %LET %BASIC$H_FLOAT_AXP_CMPLX_DCL = 1
      %END %IF
    
    
      DECLARE LONG CONSTANT LIB$K_PROC_VALUE_NULL = 0
      DECLARE LONG CONSTANT LIB$K_INVO_HANDLE_NULL = 0
      DECLARE LONG CONSTANT LIBICB$K_INVO_HANDLE_SIZE = 8
      DECLARE LONG CONSTANT LIBICB$K_INVO_CONTEXT_VERSION = 2
    !  The header quadword contains:
      DECLARE LONG CONSTANT LIBICB$M_FFLAGS_BITS = x'00FFFFFF'
      DECLARE LONG CONSTANT LIBICB$M_BOTTOM_OF_STACK = x'00000001'
      DECLARE LONG CONSTANT LIBICB$M_HANDLER_PRESENT = x'00000002'
      DECLARE LONG CONSTANT LIBICB$M_IN_PROLOGUE = x'00000004'
      DECLARE LONG CONSTANT LIBICB$M_IN_EPILOGUE = x'00000008'
      DECLARE LONG CONSTANT LIBICB$M_HAS_MEM_STK_FRAME = x'00000010'
      DECLARE LONG CONSTANT LIBICB$M_HAS_REG_STK_FRAME = x'00000020'
      DECLARE LONG CONSTANT LIBICB$K_INVO_CONTEXT_T_LENGTH = 1888
      DECLARE LONG CONSTANT LIBICB$K_SDA_COPY_LENGTH = 1960
      DECLARE LONG CONSTANT LIBICB$M_UO_FLAG_CACHE_UNWIND = x'00000001'
      DECLARE LONG CONSTANT LIBICB$M_UO_FLAG_EMULATION_MODE = x'00000002'
      DECLARE LONG CONSTANT LIBICB$K_UO_LENGTH = 88
    ! 
      DECLARE LONG CONSTANT LIBICB$m_using_client_memread = x'00000001'
      DECLARE LONG CONSTANT LIBICB$m_my_mode = x'00000006'
      DECLARE LONG CONSTANT LIBICB$K_CONTEXT_BLK_SIZE = 2080
    !  The following is an "internal" area that's reserved for use by
      DECLARE LONG CONSTANT LIBICB$K_REGION_BLK_SIZE = 1096
      DECLARE LONG CONSTANT LIBICB$K_REGIONLABEL_BLK_SIZE = 32
      DECLARE LONG CONSTANT LIBICB$K_DESCRIPTOR_BLK_SIZE = 1280
    !  Action codes:
      DECLARE LONG CONSTANT LIBICB$K_ACTION_KP_FIND_UNWIND = 1  !  override call to exe$kp_find_unwind_context
    !  prototype:
    !    uint64 sp = action_routine (enum action_code code, uint64 sp, uint64 ident);
      DECLARE LONG CONSTANT LIBICB$K_ACTION_USE_DEFAULT = -1  !  action routine return value to "use default"
    !  Alert codes:  (matches _UNW_ReturnCode enum in unwind.h)
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_KRNL_SAV_STATE = -2  !  _UNW_STEP_KERNEL_SAVE_STATE = -2
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_BOTTOM = -1  !  _UNW_STEP_BOTTOM
      DECLARE LONG CONSTANT LIBICB$K_AC_OK = 0  !  _UNW_OK = 0
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_ERROR = 1  !  _UNW_STEP_ERROR
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_INVALID_IP = 2  !  _UNW_STEP_INVALID_IP
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_INVALID_SP = 3  !  _UNW_STEP_INVALID_SP
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_INVALID_GR = 4  !  _UNW_STEP_INVALID_GR
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_INVALID_PFS = 5  !  _UNW_STEP_INVALID_PFS
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_INVALID_RSC = 6  !  _UNW_STEP_INVALID_RSC
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_INVALID_BSP = 7  !  _UNW_STEP_INVALID_BSP
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_INV_BSPSTORE = 8  !  _UNW_STEP_INVALID_BSPSTORE
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_INVALID_CFM = 9  !  _UNW_STEP_INVALID_CFM
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_INVALID_BR = 10  !  _UNW_STEP_INVALID_BR
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_BAD_BSP_ALIGN = 11  !  _UNW_STEP_BAD_BSP_ALIGNMENT
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_INVALID_RNAT = 12  !  _UNW_STEP_INVALID_RNAT
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_NODSC4_NONLEAF = 13  !  _UNW_STEP_NO_DESCRIPTOR_FOR_NON_LEAF
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_CORRUPT_DESC = 14  !  _UNW_STEP_CORRUPT_DESCRIPTOR
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_RSE_NOT_FLUSHD = 15  !  _UNW_STEP_RSE_NOT_FLUSHED
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_SIGNAL_CONTEXT = 16  !  _UNW_STEP_SIGNAL_CONTEXT
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_BAD_STATE = 17  !  _UNW_STEP_NOT_ALLOWED_IN_STATE
      DECLARE LONG CONSTANT LIBICB$K_AC_INIT_RANGE_ERROR = 18  !  _UNW_INITIALIZATION_RANGE_ERROR
      DECLARE LONG CONSTANT LIBICB$K_AC_QUERY_RANGE_ERROR = 19  !  _UNW_QUERY_RANGE_ERROR
      DECLARE LONG CONSTANT LIBICB$K_AC_QUERY_INVALID_ERROR = 20  !  _UNW_QUERY_INVALID_ERROR
      DECLARE LONG CONSTANT LIBICB$K_AC_SET_BAD_STATE = 21  !  _UNW_SET_NOT_ALLOWED_IN_STATE
      DECLARE LONG CONSTANT LIBICB$K_AC_CURR_CTXT_FAILED = 22  !  _UNW_CURRENT_CONTEXT_FAILED
      DECLARE LONG CONSTANT LIBICB$K_AC_CURR_CTXT_BAD_STATE = 23  !  _UNW_CURRENT_CONTEXT_NOT_ALLOWED_IN_STATE
      DECLARE LONG CONSTANT LIBICB$K_AC_MEMORY_ALLOC_ERROR = 24  !  _UNW_MEMORY_ALLOCATION_ERROR
      DECLARE LONG CONSTANT LIBICB$K_AC_CLEAR_BAD_STATE = 25  !  _UNW_CLEAR_NOT_ALLOWED_IN_STATE
      DECLARE LONG CONSTANT LIBICB$K_AC_QUERY_BAD_STATE = 26  !  _UNW_QUERY_NOT_ALLOWED_IN_STATE
      DECLARE LONG CONSTANT LIBICB$K_AC_INTERNAL_ERROR = 27  !  _UNW_INTERNAL_ERROR
      DECLARE LONG CONSTANT LIBICB$K_AC_STEP_I_ABI_MISMATCH = 28  !  _UNW_STEP_INTERRUPTION_ABI_MISMATCH
      DECLARE LONG CONSTANT LIBICB$K_AC_UNALIGNED_ICB = 29  !  _UNW_UNALIGNED_ICB
      DECLARE LONG CONSTANT LIBICB$K_AC_READ_MEM_FAILURE = 30  !  _UNW_READ_MEMORY_FAILURE
      DECLARE LONG CONSTANT LIBICB$K_AC_WRITE_MEM_FAILURE = 31  !  _UNW_WRITE_MEMORY_FAILURE
      DECLARE LONG CONSTANT LIBICB$K_AC_WRITE_REG_FAILURE = 32  !  _UNW_WRITE_REGISTER_FAILURE
      DECLARE LONG CONSTANT LIBICB$K_AC_UO_INCON_CALLBACK = 33  !  _UNW_USER_OVERRIDE_INCONSISTENT_CALLBACK_PARAM
      DECLARE LONG CONSTANT LIBICB$K_AC_PUT_REG_INVALID = 34  !  _UNW_PUT_REGISTER_INVALID
      DECLARE LONG CONSTANT LIBICB$K_INVO_CONTEXT_BLK_SIZE = 2112
      DECLARE LONG CONSTANT LIBICB$S_INVO_CONTEXT_BLK = 2112
      record INVO_CONTEXT_BLK
    ! 
    ! 	 The length of the structure in bytes (a longword field),
    ! 	 The frame flags (a 3 byte field of bits), and
    ! 	 The version number (a 1 byte field)
         group LIBICB$R_HDR
            variant
               case
                  BASIC$QUADWORD LIBICB$IH_HEADER  !  Header (length, flags, version)
               case
                  group LIBICB$R_HDR_DESC
                     LONG LIBICB$L_CONTEXT_LENGTH
                     group LIBICB$R_FRAMEFLAGS
                        variant
                        case
                           LONG FFLAGS_BITS_bits   ! COMMENT ADDED BY SDL - FFLAGS_BITS_bits contains bits FFLAGS_BITS through  &
 ! FFLAGS_BITS
                        case
                           group LIBICB$R_FFLAGS_DESC
                              BYTE BOTTOM_OF_STACK_bits   ! COMMENT ADDED BY SDL - BOTTOM_OF_STACK_bits contains bits  &
 ! BOTTOM_OF_STACK through FILL_0_
                           end group LIBICB$R_FFLAGS_DESC
                        end variant
                     end group LIBICB$R_FRAMEFLAGS
                     BYTE LIBICB$B_BLOCK_VERSION
                  end group LIBICB$R_HDR_DESC
            end variant
         end group LIBICB$R_HDR
         BASIC$QUADWORD LIBICB$ih_spare_01  !  Start of context_t must be octaword aligned
    ! ***** Start of context_t ******************
    ! 
    !  a context_t structure should be octaword (16-byte) aligned, and is passed by
    !  reference to the "get initial context" callback routine and establishes
    !  the "current" state of the machine and forms the inital context for for unwinding.
    !  
         group LIBICB$r_i_reg
            variant
               case
                  BASIC$QUADWORD LIBICB$IH_IREG ( 127 )  !  General (integer) Registers
    !  32 static registers, plus
    !  up to 96 stacked/rotating registers
               case
                  group LIBICB$r_i_overlay
                     BASIC$QUADWORD LIBICB$ih_i_used0  !  R0
                     BASIC$QUADWORD LIBICB$IH_GP  !  synonym for R1 (Global Data Pointer)
                     BASIC$QUADWORD LIBICB$ih_i_used1 ( 2 to 11 )  !  R2 - R11
                     BASIC$QUADWORD LIBICB$IH_SP  !  synonym for R12 (Memory Stack Pointer)
                     BASIC$QUADWORD LIBICB$IH_TP  !  synonym for R13 (Thread Pointer)
                     BASIC$QUADWORD LIBICB$ih_i_used2 ( 14 to 24 )  !  R14 - R24
                     BASIC$QUADWORD LIBICB$IH_AI  !  synonym for R25 (Argument Information register)
                     BASIC$QUADWORD LIBICB$ih_i_used3 ( 26 to 127 )  !  R26 - R127
                  end group LIBICB$r_i_overlay
            end variant
         end group LIBICB$r_i_reg
         BASIC$QUADWORD LIBICB$IH_GRNAT ( 1 )  !  General Register NaT Collection Registers
         BASIC$OCTAWORD LIBICB$FO_F2_F31 ( 2 to 31 )  !  Floating Point Registers.
    !  32 static floating point registers.
    !  Floating Point Registers are 82 bits wide
    !  but stored here in octawords.
         BASIC$QUADWORD LIBICB$PH_F32_F127  !  Pointer to upper Floating Register save
    !  area.  Zero if not saved.
         BASIC$QUADWORD LIBICB$IH_BRANCH ( 7 )  !  Branch Registers
    !  Application Registers (ARs)
    ! 
         BASIC$QUADWORD LIBICB$IH_RSC       !  Register Stack Configuration Register
         BASIC$QUADWORD LIBICB$IH_BSP       !  Backing store pointer
         BASIC$QUADWORD LIBICB$IH_BSPSTORE  !  Backing store write pointer
         BASIC$QUADWORD LIBICB$IH_RNAT      !  RSE NaT Collection Register
         BASIC$QUADWORD LIBICB$IH_CCV       !  Compare ? Exchange Value Register
         BASIC$QUADWORD LIBICB$IH_UNAT      !  User NaT Collection Register
         BASIC$QUADWORD LIBICB$FH_FPSR      !  OBSOLETE - do not rely on the contents of this field.
         BASIC$QUADWORD LIBICB$IH_PFS       !  Previous Function State
         BASIC$QUADWORD LIBICB$IH_LC        !  Loop Count Register
         BASIC$QUADWORD LIBICB$IH_EC        !  Epilogue Count Register
         BASIC$QUADWORD LIBICB$IH_CSD       !  Copy of AR.CSD
         BASIC$QUADWORD LIBICB$IH_SSD       !  Copy of AR.SSD
    ! 
    !  End ARs
         BASIC$QUADWORD LIBICB$Q_PRED       !  Predicate Collection Register, PR0-PR63
         BASIC$QUADWORD LIBICB$IH_PC        !  Current PC (Instruction Pointer + slot)
         group LIBICB$r_cfm_u
            variant
               case
                  BASIC$QUADWORD LIBICB$IH_CFM  !  Current Frame Marker
               case
                  group LIBICB$r_cfm_s
                      !  Size of stack frame 
                      !  Size of locals portion of stack frame 
                      !  Size of rotating portion of stack frame 
                      !  Register Rename Base for General Registers
                      !  Register Rename Base for Floating-point Registers
                      !  Register Rename Base for Predicate Registers
                     BYTE SOF_bits ( 5 )   ! COMMENT ADDED BY SDL - SOF_bits contains bits SOF through FILL_1_
                  end group LIBICB$r_cfm_s
            end variant
         end group LIBICB$r_cfm_u
         group LIBICB$r_um_u
            variant
               case
                  BASIC$QUADWORD LIBICB$IH_UM  !  User Mask bits of the PSR.
               case
                  group LIBICB$r_um_s
                      !  Reserved
                      !  Big-endian memory access enable
                      !  User performance monitor enable
                      !  Alignment check data memory references
                      !  Lower (F2-F31) Floating-point registers written
                      !  Upper (F32-F127) Floating-point registers written
                     BYTE rv_bits   ! COMMENT ADDED BY SDL - rv_bits contains bits rv through FILL_2_
                  end group LIBICB$r_um_s
            end variant
         end group LIBICB$r_um_u
         BASIC$QUADWORD LIBICB$ih_next_bsp  !  Next frame's Backing Store Pointer (Internal use)
         BASIC$QUADWORD LIBICB$ih_next_pfs  !  Next frame's Previous Frame State (Internal use)
    !  The following two locations are used when walking from an inner
    !  mode stack to an outer mode and context has been saved in a INTSK structure,
    !  but the outer mode stacked registers have bee saved on the inner mode RSE backing store.
    ! 
         BASIC$QUADWORD LIBICB$ih_bspbase   !  Base for outer mode stacked registers saved in
    !  inner mode RSE backing store (Internal use)
         BASIC$QUADWORD LIBICB$ih_intstk_rnat  !  RNAT as saved in INTSTK (Internal use)
    !  the following "valid" bitmasks are used to record the validity
    !  of a given register for this context
         BASIC$OCTAWORD LIBICB$O_GR_VALID   !  General Register validity mask
         LONG LIBICB$L_FR_VALID             !  F2 - F31 validity mask (bit 2 for F2)
         LONG LIBICB$l_fr_valid_fill
         BASIC$QUADWORD LIBICB$Q_BR_VALID   !  Branch Register validity mask
         group LIBICB$r_ar_valid_u
            variant
               case
                  BASIC$QUADWORD LIBICB$Q_AR_VALID  !  Application Register validity mask
               case
                  group LIBICB$r_ar_valid_s
                      !  Register Stack Configuration Register
                      !  Backing store pointer
                      !  Backing store write pointer
                      !  RSE NaT Collection Register
                      !  Compare ? Exchange Value Register
                      !  User NaT Collection Register
                      !  Floating Point Status Register.
                      !  Previous Function State
                      !  Loop Count Register
                      !  Epilogue Count Register
                      !  Copy of AR.CSD
                      !  Copy of AR.SSD
                     WORD RSC_VALID_bits   ! COMMENT ADDED BY SDL - RSC_VALID_bits contains bits RSC_VALID through FILL_3_
                  end group LIBICB$r_ar_valid_s
            end variant
         end group LIBICB$r_ar_valid_u
         group LIBICB$r_other_valid_u
            variant
               case
                  BASIC$QUADWORD LIBICB$Q_OTHER_VALID  !  PC, CFM  validity mask
               case
                  group LIBICB$r_other_valid_s
                      !  Current PC
                      !  Current Frame Marker
                      !  User Mask field of PSR.
                     BYTE PC_VALID_bits   ! COMMENT ADDED BY SDL - PC_VALID_bits contains bits PC_VALID through FILL_4_
                  end group LIBICB$r_other_valid_s
            end variant
         end group LIBICB$r_other_valid_u
         BASIC$QUADWORD LIBICB$Q_PR_VALID   !  Predicate Register validity mask
         BASIC$QUADWORD LIBICB$IH_ORIGINAL_SPILL_ADDR  !  Original address of GR spill area (?LIBICB$IH_IREG[0])
    !  (needed for NaT bit podition calculations)
         BASIC$QUADWORD LIBICB$ih_true_psp  !  True Previous SP (for Invo Handle)
         BASIC$QUADWORD LIBICB$ih_spare_03
         BASIC$QUADWORD LIBICB$ih_spare_04
         BASIC$QUADWORD LIBICB$ih_spare_05
         BASIC$QUADWORD LIBICB$ih_spare_06
         BASIC$QUADWORD LIBICB$ih_spare_07
         BASIC$QUADWORD LIBICB$ih_spare_08
    ! 
    ! ******* End of context_t structure *********************
         BASIC$QUADWORD LIBICB$IH_PSP       !  SP at entry to routine (Previous SP)
         BASIC$QUADWORD LIBICB$ih_psp_valid  !  PreviousSP valid
         BASIC$QUADWORD LIBICB$IH_RETURN_PC  !  Return PC for SDA.
         BASIC$QUADWORD LIBICB$IH_PREV_BSP  !  BSP of preceding frame for SDA.
         BASIC$QUADWORD LIBICB$PH_CHFCTX_ADDR  !  Pointer to condition handler facility context block
         BASIC$QUADWORD LIBICB$PH_OTHER     !  Pointer to other interesting structure (if any)
         BASIC$QUADWORD LIBICB$IH_OSSD      !  Copy of OSSD from Unwind Information Block
         BASIC$QUADWORD LIBICB$IH_HANDLER_FV  !  Condition Handler Function Value
         BASIC$QUADWORD LIBICB$PH_LSDA      !  Virtual Address of LSD area of UIB
         BASIC$QUADWORD LIBICB$ph_desc      !  Pointer to _Unwind_Descriptor structure (Internal use)
         BASIC$QUADWORD LIBICB$ph_history   !  Pointer to _Unwind_History structure (Internal use)
    ! ******* Start of User Override *************************
    ! 
    !   The following locations can be used to alter the default behavior
    !   Typically this would be used for cross-process unwinding, and
    !   specifying an alternative memory allocation scheme.
         group LIBICB$r_op_flags
            variant
               case
                  LONG LIBICB$R_UO_BASE     !  base of User Override area
               case
                  BASIC$QUADWORD LIBICB$Q_UO_FLAGS  !  operational flags
               case
                  group LIBICB$r_uo_flag_bits
    !  cache unwind information between calls
    !  for effiecient stack walk.
                      !  Internal use only
                     BYTE UO_FLAG_CACHE_UNWIND_bits   ! COMMENT ADDED BY SDL - UO_FLAG_CACHE_UNWIND_bits contains bits  &
 ! UO_FLAG_CACHE_UNWIND through FILL_5_
                  end group LIBICB$r_uo_flag_bits
            end variant
         end group LIBICB$r_op_flags
         BASIC$QUADWORD LIBICB$IH_UO_IDENT  !  user context variable, passed by value
    !  to the following callback routines.
         BASIC$QUADWORD LIBICB$PH_UO_READ_MEM  !  Pointer to user "read memory" routine
         BASIC$QUADWORD LIBICB$PH_UO_GETUEINFO  !  Pointer to user "get Unwind Entry Information" routine
         BASIC$QUADWORD LIBICB$PH_UO_GETCONTEXT  !  Pointer to user "get Initial Context" routine
         BASIC$QUADWORD LIBICB$PH_UO_WRITE_MEM  !  Pointer to user "put memory" routine
         BASIC$QUADWORD LIBICB$PH_UO_WRITE_REG  !  Pointer to user "put register" routine
         BASIC$QUADWORD LIBICB$PH_UO_MALLOC  !  Pointer to user "malloc" routine
         BASIC$QUADWORD LIBICB$PH_UO_FREE   !  Pointer to user "free" routine
         BASIC$QUADWORD LIBICB$PH_UO_ACTION_ROUTINE  !  Pointer to user "action" routine - actions 
    !  are defined by "action codes" (see below).
         BASIC$QUADWORD LIBICB$ih_spare_10
    ! ******* End of User Override area ***************************
    !  the following locations are used internally, and should not be
    !  modified by the user
         BASIC$QUADWORD LIBICB$ph_most_recent_context  !  Most recent user context used
         group LIBICB$r_int_flags
            variant
               case
                  LONG LIBICB$l_internal_flags  !  internal operational flags
               case
                  group LIBICB$r_int_flag_bits
                     BYTE using_client_memread_bits   ! COMMENT ADDED BY SDL - using_client_memread_bits contains bits  &
 ! using_client_memread through FILL_6_
                  end group LIBICB$r_int_flag_bits
            end variant
         end group LIBICB$r_int_flags
         LONG LIBICB$l_interface_state      !  enum InterfaceUsageState
         LONG LIBICB$l_ip_source            !  enum IP_SOURCE
    !  The alert code can be examined to a more detailed failure status
         LONG LIBICB$L_ALERT_CODE           !  enum _UNW_ReturnCode
         BASIC$QUADWORD LIBICB$ih_spare_11
         STRING LIBICB$t_align_2 = 0
    !  the operating system. It's size may vary over time.
         BASIC$QUADWORD LIBICB$IH_SYSTEM_DEFINED ( 1 )
    ! 
    !    Action codes are passed as the first parameter to the UO_ACTION_ROUTINE to indicate
    !    an action to be performed.  The remaining parameters to the action routine are action
    !    dependent, and usually include the ident value as the last parameter.
    ! 
    !    Action routine prototype:
    ! 
    !       uint64 return_value = action_routine (enum action_code code, ..., uint64 ident);
    ! 
    !    A return_value of ACTION_USE_DEFAULT indicates that the action was not performed
    !    and the calling standard routines should fall back to "default" processing.
    !    Other return values are action dependent.
    ! 
      end record INVO_CONTEXT_BLK
    
    !  Write Register callback routine - WhichReg enum.
    ! 
    !  The Write Register callback routine is only used when a live
    !  register in another (remote) process needs to be written as
    !  a result of a call to LIB$I64_PUT_INVO_REGISTERS.
    !  It is permissible to implement a subset of these registers,
    !  or not implement it at all if you are sure that these registers
    !  have been saved to memory before PUT_INVO is called
    ! 
    !  For the General Registers:
    !    whichReg = LIBICB$K_WhichReg_GR0 + register number
    !    value_1  = 64-bit register value
    !    value_2  = 0, or 1 for NaT bit value
    ! 
      DECLARE LONG CONSTANT LIBICB$K_WhichReg_GR0 = 0
    ! 
    !  For the Floating Registers:
    !    whichReg = LIBICB$K_WhichReg_FR0 + floating register number
    !    value_1  = 64-bit lower floating fill value
    !    value_2  = 64-bit upper floating fill value
    ! 
      DECLARE LONG CONSTANT LIBICB$K_WhichReg_FR0 = 128
    ! 
    !  For the Predicate Registers:
    !    whichReg = LIBICB$K_WhichReg_PR0 + predicate register number
    !    value_1  = 0, or 1 rgister (bit) value
    !    value_2  = ignored
    ! 
      DECLARE LONG CONSTANT LIBICB$K_WhichReg_PR0 = 256
    ! 
    !  For the Branch Registers:
    !    whichReg = LIBICB$K_WhichReg_BR0 + branch register number
    !    value_1  = 64-bit register value
    !    value_2  = ignored
    ! 
      DECLARE LONG CONSTANT LIBICB$K_WhichReg_BR0 = 320
    ! 
    !  For the Floating Point Status Register:
    !    whichReg = LIBICB$K_WhichReg_FPSR
    !    value_1  = 64-bit register value
    !    value_2  = ignored
    ! 
      DECLARE LONG CONSTANT LIBICB$K_WhichReg_FPSR = 328