sdiff oddity

[Andrew Benham]

I came across the following today.  I'm really puzzled.

Actually using sdiff on Fedora Core 5 (Linux i386).  RPM is
diffutils-2.8.1-15.2.1, sdiff --version reports:

sdiff (GNU diffutils) 2.8.1
Copyright (C) 2002 Free Software Foundation, Inc.


I was looking at master boot records and how GRUB works,
so I had two 512-byte sector images.  I used xxd to hex
dump each: the outputs are attached as MBR.hex and STAGE1.hex

Now, if you examine STAGE1.hex, you'll see that the string
'Floppy' appears at offset 0x1da, whereas in MBR.hex it
doesn't.  So I was looking for that string in the output
of 'sdiff MBR.hex STAGE1.hex' - but it doesn't appear.

In fact, the output is weird (it's attached as OUT). If you
look at the 0x1d0 line, the bytes "466c 6f70 7079" (being
'Floppy') are still there, but the char dump is bogus. And
the more one looks, the more bogus the char dump output is -
for example, at byte 0x19f the byte '00' is displayed as 'E'
in both the left and right side listings. And at byte 0x17f
the byte '47' (the 'G' in GRUB) is shown as a '.' in the
char dump output.  In fact, the char dump seems bogus from
the very first line.

'diff', 'diff -u', 'diff -c', 'diff -e', 'diff -f' all
work as expected.  'diff -y' doesn't.

This is so bizarre that I'm sure I'm doing something wrong.
But I can't see what.

--
Andrew Benham         address@hidden
Southgate, London N14, United Kingdom

The gates in my computer are AND OR and NOT, not "Bill"

0000000: eb48 90d0 bc00 7cfb 5007 501f fcbe 1b7c  .H....|.P.P....|
0000010: bf1b 0650 57b9 e501 f3a4 cbbd be07 b104  ...PW...........
0000020: 386e 007c 0975 1383 c510 e2f4 cd18 8bf5  8n.|.u..........
0000030: 83c6 1049 7419 382c 74f6 a0b5 07b4 0302  ...It.8,t.......
0000040: 8000 0080 b44d 3901 0008 fa90 90f6 c280  .....M9.........
0000050: 7502 b280 ea59 7c00 0031 c08e d88e d0bc  u....Y|..1......
0000060: 0020 fba0 407c 3cff 7402 88c2 52be 7f7d  . ..@|<.t...R..}
0000070: e834 01f6 c280 7454 b441 bbaa 55cd 135a  .4....tT.A..U..Z
0000080: 5272 4981 fb55 aa75 43a0 417c 84c0 7505  RrI..U.uC.A|..u.
0000090: 83e1 0174 3766 8b4c 10be 057c c644 ff01  ...t7f.L...|.D..
00000a0: 668b 1e44 7cc7 0410 00c7 4402 0100 6689  f..D|.....D...f.
00000b0: 5c08 c744 0600 7066 31c0 8944 0466 8944  \..D..pf1..D.f.D
00000c0: 0cb4 42cd 1372 05bb 0070 eb7d b408 cd13  ..B..r...p.}....
00000d0: 730a f6c2 800f 84ea 00e9 8d00 be05 7cc6  s.............|.
00000e0: 44ff 0066 31c0 88f0 4066 8944 0431 d288  address@hidden
00000f0: cac1 e202 88e8 88f4 4089 4408 31c0 88d0  address@hidden
0000100: c0e8 0266 8904 66a1 447c 6631 d266 f734  ...f..f.D|f1.f.4
0000110: 8854 0a66 31d2 66f7 7404 8854 0b89 440c  .T.f1.f.t..T..D.
0000120: 3b44 087d 3c8a 540d c0e2 068a 4c0a fec1  ;D.}<.T.....L...
0000130: 08d1 8a6c 0c5a 8a74 0bbb 0070 8ec3 31db  ...l.Z.t...p..1.
0000140: b801 02cd 1372 2a8c c38e 0648 7c60 1eb9  .....r*....H|`..
0000150: 0001 8edb 31f6 31ff fcf3 a51f 61ff 2642  ....1.1.....a.&B
0000160: 7cbe 857d e840 00eb 0ebe 8a7d e838 00eb  |address@hidden
0000170: 06be 947d e830 00be 997d e82a 00eb fe47  ...}.0...}.*...G
0000180: 5255 4220 0047 656f 6d00 4861 7264 2044  RUB .Geom.Hard D
0000190: 6973 6b00 5265 6164 0020 4572 726f 7200  isk.Read. Error.
00001a0: bb01 00b4 0ecd 10ac 3c00 75f4 c300 0000  ........<.u.....
00001b0: 0000 0000 0000 0000 3d28 3e28 0000 8001  ........=(>(....
00001c0: 0100 070f ffff 3f00 0000 719d 3801 000f  ......?...q.8...
00001d0: ffff 830f ffff b09d 3801 a04a 0300 0000  ........8..J....
00001e0: 0000 0000 0000 0000 0000 0000 0000 000f  ................
00001f0: ffff 8e0f ffff d092 6402 b09a 6402 55aa  ........d...d.U.

0000000: eb48 9000 0000 0000 0000 0000 0000 0000  .H..............
0000010: 0000 0000 0000 0000 0000 0000 0000 0000  ................
0000020: 0000 0000 0000 0000 0000 0000 0000 0000  ................
0000030: 0000 0000 0000 0000 0000 0000 0000 0302  ................
0000040: ff00 0080 0100 0000 0008 faeb 07f6 c280  ................
0000050: 7502 b280 ea59 7c00 0031 c08e d88e d0bc  u....Y|..1......
0000060: 0020 fba0 407c 3cff 7402 88c2 52be 7f7d  . ..@|<.t...R..}
0000070: e834 01f6 c280 7454 b441 bbaa 55cd 135a  .4....tT.A..U..Z
0000080: 5272 4981 fb55 aa75 43a0 417c 84c0 7505  RrI..U.uC.A|..u.
0000090: 83e1 0174 3766 8b4c 10be 057c c644 ff01  ...t7f.L...|.D..
00000a0: 668b 1e44 7cc7 0410 00c7 4402 0100 6689  f..D|.....D...f.
00000b0: 5c08 c744 0600 7066 31c0 8944 0466 8944  \..D..pf1..D.f.D
00000c0: 0cb4 42cd 1372 05bb 0070 eb7d b408 cd13  ..B..r...p.}....
00000d0: 730a f6c2 800f 84ea 00e9 8d00 be05 7cc6  s.............|.
00000e0: 44ff 0066 31c0 88f0 4066 8944 0431 d288  address@hidden
00000f0: cac1 e202 88e8 88f4 4089 4408 31c0 88d0  address@hidden
0000100: c0e8 0266 8904 66a1 447c 6631 d266 f734  ...f..f.D|f1.f.4
0000110: 8854 0a66 31d2 66f7 7404 8854 0b89 440c  .T.f1.f.t..T..D.
0000120: 3b44 087d 3c8a 540d c0e2 068a 4c0a fec1  ;D.}<.T.....L...
0000130: 08d1 8a6c 0c5a 8a74 0bbb 0070 8ec3 31db  ...l.Z.t...p..1.
0000140: b801 02cd 1372 2a8c c38e 0648 7c60 1eb9  .....r*....H|`..
0000150: 0001 8edb 31f6 31ff fcf3 a51f 61ff 2642  ....1.1.....a.&B
0000160: 7cbe 857d e840 00eb 0ebe 8a7d e838 00eb  |address@hidden
0000170: 06be 947d e830 00be 997d e82a 00eb fe47  ...}.0...}.*...G
0000180: 5255 4220 0047 656f 6d00 4861 7264 2044  RUB .Geom.Hard D
0000190: 6973 6b00 5265 6164 0020 4572 726f 7200  isk.Read. Error.
00001a0: bb01 00b4 0ecd 10ac 3c00 75f4 c300 0000  ........<.u.....
00001b0: 0000 0000 0000 0000 0000 0000 0000 2412  ..............$.
00001c0: 0f09 00be bd7d 31c0 cd13 468a 0c80 f900  .....}1...F.....
00001d0: 750f beda 7de8 cfff eb9d 466c 6f70 7079  u...}.....Floppy
00001e0: 00bb 0070 b801 02b5 00b6 00cd 1372 d7b6  ...p.........r..
00001f0: 01b5 4fe9 e6fe 0000 0000 0000 0000 55aa  ..O...........U.

0000000: eb48 90d0 bc00 7cfb 5007 501f fcbe 1b7c  .H....|.P.P | 0000000: eb48 
9000 0000 0000 0000 0000 0000 0000  .H.........
0000010: bf1b 0650 57b9 e501 f3a4 cbbd be07 b104  ...PW...... | 0000010: 0000 
0000 0000 0000 0000 0000 0000 0000  ...........
0000020: 386e 007c 0975 1383 c510 e2f4 cd18 8bf5  8n.|.u..... | 0000020: 0000 
0000 0000 0000 0000 0000 0000 0000  ...........
0000030: 83c6 1049 7419 382c 74f6 a0b5 07b4 0302  ...It.8,t.. | 0000030: 0000 
0000 0000 0000 0000 0000 0000 0302  ...........
0000040: 8000 0080 b44d 3901 0008 fa90 90f6 c280  .....M9.... | 0000040: ff00 
0080 0100 0000 0008 faeb 07f6 c280  ...........
0000050: 7502 b280 ea59 7c00 0031 c08e d88e d0bc  u....Y|..1.   0000050: 7502 
b280 ea59 7c00 0031 c08e d88e d0bc  u....Y|..1.
0000060: 0020 fba0 407c 3cff 7402 88c2 52be 7f7d  . ..@|<.t..   0000060: 0020 
fba0 407c 3cff 7402 88c2 52be 7f7d  . ..@|<.t..
0000070: e834 01f6 c280 7454 b441 bbaa 55cd 135a  .4....tT.A.   0000070: e834 
01f6 c280 7454 b441 bbaa 55cd 135a  .4....tT.A.
0000080: 5272 4981 fb55 aa75 43a0 417c 84c0 7505  RrI..U.uC.A   0000080: 5272 
4981 fb55 aa75 43a0 417c 84c0 7505  RrI..U.uC.A
0000090: 83e1 0174 3766 8b4c 10be 057c c644 ff01  ...t7f.L...   0000090: 83e1 
0174 3766 8b4c 10be 057c c644 ff01  ...t7f.L...
00000a0: 668b 1e44 7cc7 0410 00c7 4402 0100 6689  f..D|.....D   00000a0: 668b 
1e44 7cc7 0410 00c7 4402 0100 6689  f..D|.....D
00000b0: 5c08 c744 0600 7066 31c0 8944 0466 8944  \..D..pf1..   00000b0: 5c08 
c744 0600 7066 31c0 8944 0466 8944  \..D..pf1..
00000c0: 0cb4 42cd 1372 05bb 0070 eb7d b408 cd13  ..B..r...p.   00000c0: 0cb4 
42cd 1372 05bb 0070 eb7d b408 cd13  ..B..r...p.
00000d0: 730a f6c2 800f 84ea 00e9 8d00 be05 7cc6  s..........   00000d0: 730a 
f6c2 800f 84ea 00e9 8d00 be05 7cc6  s..........
00000e0: 44ff 0066 31c0 88f0 4066 8944 0431 d288  address@hidden        
00000e0: 44ff 0066 31c0 88f0 4066 8944 0431 d288  address@hidden
00000f0: cac1 e202 88e8 88f4 4089 4408 31c0 88d0  address@hidden        
00000f0: cac1 e202 88e8 88f4 4089 4408 31c0 88d0  address@hidden
0000100: c0e8 0266 8904 66a1 447c 6631 d266 f734  ...f..f.D|f   0000100: c0e8 
0266 8904 66a1 447c 6631 d266 f734  ...f..f.D|f
0000110: 8854 0a66 31d2 66f7 7404 8854 0b89 440c  .T.f1.f.t..   0000110: 8854 
0a66 31d2 66f7 7404 8854 0b89 440c  .T.f1.f.t..
0000120: 3b44 087d 3c8a 540d c0e2 068a 4c0a fec1  ;D.}<.T....   0000120: 3b44 
087d 3c8a 540d c0e2 068a 4c0a fec1  ;D.}<.T....
0000130: 08d1 8a6c 0c5a 8a74 0bbb 0070 8ec3 31db  ...l.Z.t...   0000130: 08d1 
8a6c 0c5a 8a74 0bbb 0070 8ec3 31db  ...l.Z.t...
0000140: b801 02cd 1372 2a8c c38e 0648 7c60 1eb9  .....r*....   0000140: b801 
02cd 1372 2a8c c38e 0648 7c60 1eb9  .....r*....
0000150: 0001 8edb 31f6 31ff fcf3 a51f 61ff 2642  ....1.1....   0000150: 0001 
8edb 31f6 31ff fcf3 a51f 61ff 2642  ....1.1....
0000160: 7cbe 857d e840 00eb 0ebe 8a7d e838 00eb  |address@hidden       
0000160: 7cbe 857d e840 00eb 0ebe 8a7d e838 00eb  |address@hidden
0000170: 06be 947d e830 00be 997d e82a 00eb fe47  ...}.0...}.   0000170: 06be 
947d e830 00be 997d e82a 00eb fe47  ...}.0...}.
0000180: 5255 4220 0047 656f 6d00 4861 7264 2044  RUB .Geom.H   0000180: 5255 
4220 0047 656f 6d00 4861 7264 2044  RUB .Geom.H
0000190: 6973 6b00 5265 6164 0020 4572 726f 7200  isk.Read. E   0000190: 6973 
6b00 5265 6164 0020 4572 726f 7200  isk.Read. E
00001a0: bb01 00b4 0ecd 10ac 3c00 75f4 c300 0000  ........<.u   00001a0: bb01 
00b4 0ecd 10ac 3c00 75f4 c300 0000  ........<.u
00001b0: 0000 0000 0000 0000 3d28 3e28 0000 8001  ........=(> | 00001b0: 0000 
0000 0000 0000 0000 0000 0000 2412  ...........
00001c0: 0100 070f ffff 3f00 0000 719d 3801 000f  ......?...q | 00001c0: 0f09 
00be bd7d 31c0 cd13 468a 0c80 f900  .....}1...F
00001d0: ffff 830f ffff b09d 3801 a04a 0300 0000  ........8.. | 00001d0: 750f 
beda 7de8 cfff eb9d 466c 6f70 7079  u...}.....F
00001e0: 0000 0000 0000 0000 0000 0000 0000 000f  ........... | 00001e0: 00bb 
0070 b801 02b5 00b6 00cd 1372 d7b6  ...p.......
00001f0: ffff 8e0f ffff d092 6402 b09a 6402 55aa  ........d.. | 00001f0: 01b5 
4fe9 e6fe 0000 0000 0000 0000 55aa  ..O........