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Path: utzoo!mnetor!seismo!husc6!panda!teddy!jpn
From: jpn@teddy.UUCP (John P. Nelson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Turbo C division bug
Message-ID: <4130@teddy.UUCP>
Date: Mon, 22-Jun-87 18:29:10 EDT
Article-I.D.: teddy.4130
Posted: Mon Jun 22 18:29:10 1987
Date-Received: Tue, 23-Jun-87 05:42:51 EDT
References: <105@flnexus.ATT.COM>
Reply-To: jpn@teddy.UUCP (John P. Nelson)
Organization: GenRad, Inc., Concord, Mass.
Lines: 115

>It [Turbo C] does, however, seem to have a serious bug with the floating
>point division routines. If your program does division on two constants:
>
>float x;
>
>x = 5.0/4.0;
>
>The result will be as if the division was inverted (i.e x = 4.0/5.0)

And here is the patch.  Apparently only the earliest copies are afflicted
with the bug.  Enjoy.

PRODUCT : TURBO C
VERSION : 1.0
     OS : PC-DOS
   DATE : MAY 20, 1987                                       PAGE : 1/2

  TITLE : FLOATING POINT EVALUATION - PATCH




     The following patch solves a problem with dividing floating point
     evaluation.

     To apply this patch, you will need to use the DOS utility DEBUG.COM.
     You may obtain a copy of DEBUG.COM from one of your original PC-DOS
     or  MS-DOS diskettes.

     NOTE:   1. Do not patch your original Turbo C disk, use a working or
                backup copy of TCC.EXE and TC.EXE for this patch.

             2. DEBUG is not sensitive to upper and lower case.  All ad-
                dresses are listed in upper case for ease of readibility.

             3. XXXX,YYYY,ZZZZ are hexidecimal digits returned by DEBUG.
                You must  replace these  digits accordingly when  typing
                in your commands.

             4. While in DEBUG, the prompt will appear as a dash (-).

             5. If you do not receive the appropriate response,press "q"
                followed by  <Enter>,  to exit  from DEBUG.   Check your
                version number and, if correct, try again.

             6. TCC.EXE and TC.EXE will not fit together onto a 360K disk.
                To patch both  programs on a floppy disk,  you may need to
                copy  TCC.EXE and DEBUG.COM  onto one disk and perform the
                patch.  Save the patched version of TCC.EXE to another
                disk.  Repeat the same steps using TC.EXE.

     At the  DOS prompt,  type the  following  information exactly as it
     appears (Conclude each line by pressing <Enter>).

PRODUCT : TURBO C
VERSION : 1.0
     OS : PC-DOS
   DATE : MAY 20, 1987                                       PAGE : 2/2
  TITLE : DIVISION OF CONSTANTS - PATCH

                         Patch for TCC.EXE

     Type the following:                      You will see:

     ren tcc.exe tcc.xex<Enter>               A>

     debug tcc.xex<Enter>                     -

     r<Enter>                                 ... CS=XXXX ...
                                              -

     h XXXX 2420<Enter>                       YYYY  ZZZZ
                                              -

     e YYYY:369<Enter>                        YYYY:0369   0A.

     6<Enter>                                 -

     e YYYY:36F<Enter>                        YYYY:036F   06.

     A<Enter>                                 -

     w<Enter>                                 Writing 2948A bytes

     q<Enter>                                 A>

     ren tcc.xex tcc.exe<Enter>

                             Patch for TC.EXE

     Type the following:                      You will see:

     ren tc.exe tc.xex<Enter>                 A>

     debug tc.xex<Enter>                      -

     r<Enter>                                 ... CS=XXXX ...
                                              -

     h XXXX 2D01<Enter>                       YYYY  ZZZZ
                                              -

     e YYYY:35E<Enter>                        YYYY:035E   0A.

     6<Enter>                                 -

     e YYYY:364<Enter>                        YYYY:0364   06.

     A<Enter>                                 -

     w<Enter>                                 Writing 38759 bytes

     q<Enter>                                 A>

     ren tc.xex tc.exe<Enter>