Hello, On trečiadienis 04 Gegužė 2011 11:40:43 Ibragimov Rinat wrote: > > This though is not totally clear to me. On the major architectures, > > char is signed, so I would assume that a chksum error in this area > > should have hit a lot of people already? Given that int is signed by > > default I wonder if this is the proper approach and it shouldn't rather > > be cast to signed char (signedness of char varies across the different > > architectures). > > The error only occurs when file name have characters with codes larger than > 128. All ASCII have codes lower than 127, so in that case there is no > difference. UTF-8 uses most significant bit as flag, so some charactes have > codes larger than 128. I'll explain with example: > > int check = 32; > check += buffer[j]; > > assume buffer==128, i.e. 0x80. When one adds signed char 0x80 to an > integer, signed char extents to a signed integer and becomes 0xffffff80. > It is not 0x80, as one may expect. > > But if all file names are in english, no one can face the bug. > > > Out of curiosity, you filed this from an i386 system. Did you maybe > > copy around the backup from/to any architcture including arm, armel, > > powerpc or s390? Were they somehow involved in the assumingly checksum > > error of yours? The thing behind the question is: If we "fix" the > > calculation in the direction that you propose, this would break backups > > done now on the architectures that do have char signed by default > > because it would result in a different checksum. > > No, unfortunately I don't have access to architectures other than amd64 and > i386. What I'm concerned about is that your patch may not be complete. There are more similar "checks" in ktar.cpp. As I absolutely have no idea how tar works, this will take time to handle properly (or hopefully upstream responds in the meantime). Thanks for forwarding the bug. -- Modestas Vainius <firstname.lastname@example.org>
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