OpenVMS AXPLIBO02_061 Alpha V6.1 LIBOTS ECO Summary

 
Copyright (c) Digital Equipment Corporation 1994, 1995. All rights reserved.

OP/SYS:      OpenVMS Alpha

COMPONENTS:  LIBOTS

SOURCE:      Digital Equipment Corporation

ECO INFORMATION:

     ECO Kit Name:  AXPLIBO02_061
     ECO Kits Superseded by This ECO Kit:  AXPLIBO01_061
     ECO Kit Approximate Size:  670 Blocks
     Kit Applies To:  OpenVMS Alpha V6.1, V6.1-1H1, V6.1-1H2
     System Reboot Necessary:  Yes


ECO KIT SUMMARY:

An ECO kit exists for LIBOTS on OpenVMS Alpha V6.1 through V6.1-1H2. 
This kit addresses the following problems: 
 
Problems addressed in the AXPLIBO02_061 kit:

  o  Using the compiler switch /GRANULARITY=BYTE will cause the wrong
     bits to be fetched.  This could result in user programs that
     cause data corruption.

  o  Small X-Floats in T-Float denorm range were being incorrectly
     converted to zero.

  o  T-Float denorms converted to X-Float were incorrect by a factor
     of 2.

     NOTE:  The X-Float datatype is a new datatype supported by
            OpenVMS Alpha starting with OpenVMS Alpha V6.1.  It is a 
            128 bit IEEE floating point datatype that is implemented 
            in software, specifically LIBOTS.  X-Float is represented 
            as a REAL*16 in Fortran. 


Problems addressed in the AXPLIBO01_061 kit:

  o  The LIBOTS routine OTS$INSV_VOL can write values to the wrong
     address and corrupt data.

     The LIBOTS INSV/EXTV corruption can be seen if a volatile 
     longword doesn't start on a byte-boundary.  This can seen 
     in languages like C and Pascal when dealing with poorly aligned
     data. 

     For Pascal, you can see it with a record like:

        type r = packed record
                 f1 : boolean;
                 f2 : integer;
                end;

     For C, you can see it with a record like:

        #pragma nomember_alignment
        struct r {

            unsigned f1 : 1;
            unsigned f2 : 32;
           };

    Given a Pascal user's tendency to use the PACKED keyword, the
    problem is more likely to occur in Pascal rather than C.  C users
    would have to go out of their way to use a 32-bit bitfield which
    is not very common.  This problem can also be seen from BLISS and 
    possibly Ada. 


INSTALLATION NOTES:

In order for the corrections in this kit to take effect, the system
must be rebooted.  If the system is a member of a VMScluster, the entire
cluster should be rebooted in order to make use of the new image(s).

Colorado Site
Georgia Site

axplibo02_061_libots.README
axplibo02_061.CHKSUM
axplibo02_061.a-dcx_axpexe