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  1. #1
    Join Date
    Nov 2015
    Posts
    21

    Default BC4 bails out for large files?

    Continuing my testing of BC4 I found that it erroneously declares two large files identical if no differences are found within the initial 13-15MB of data. I'm not sure about the limits, they also seem to vary. Uploading an example pair is hopeless but you can artificially create a pair like below:

    dd if=/dev/zero bs=1M seek=32 count=0 of=bc4test.a
    echo a >> bc4test.a
    dd if=/dev/zero bs=1M seek=32 count=0 of=bc4test.b
    echo b >> bc4test.b

    bcompare bc4test.a bc4test.b

    and see what happens.

    On my system the files are reported equal while only the initial ~13MB diff is shown in the Hexview.

    BC3 does work fine in such cases.

    btw, would be nice to know what are the size limits that BC3, BC4 are supposed to handle safely (naturally, assuming plenty of RAM memory is available).

    Regards,
    /Mikko

  2. #2
    Join Date
    Oct 2007
    Location
    Madison, WI
    Posts
    11,949

    Default

    I am not seeing the same behavior on my test system. Running these commands on these files results in detecting they are different and launching the Hex Compare. Can you email us at support@scootersoftware.com with your BCSupport.zip (Help menu -> Support; Export)? Please include a link back to this forum thread in the email for our reference.

    What kind of custom brew Fedora are you running?
    Aaron P Scooter Software

  3. #3
    Join Date
    Nov 2015
    Posts
    21

    Default

    I'm running ~Fedora 23 with custom updates from rawhide but nothing really special, as far I can tell...
    BCSupport.zip is attached and the failure happens from a clean, generic 'user' account with a trial license and Pro features on.

    If I reopen the session from within BC4 then the comparison works fine, looks to fail only when started with the files as arguments on command line, perhaps another startup synchronisation thing...

    I've tried the trick with older glibc (official Fedora releases) but with vers. 2.20 BC4 crashes at start and with 2.21 it fails just as described with 2.22.

    /M
    Attached Files Attached Files
    Last edited by mikko; 20-Nov-2015 at 11:39 AM.

  4. #4
    Join Date
    Dec 2007
    Location
    U.S. East coast
    Posts
    303

    Default

    Ubuntu 12.04.5 64-bit
    BC Version 4.1.2 (build 20720) 64-bit

    I get the same results as mikko on those two test files (bc4test.a and bc4test.b). BC4 says the files are identical, and only displays the first 13303807 (hex CAFFFF) bytes.

    By comparison:
    Code:
    $ diff -s /tmp/bc4test.a /tmp/bc4test.b
    Binary files /tmp/bc4test.a and /tmp/bc4test.b differ
    Last edited by Dave_L; 20-Nov-2015 at 02:55 PM.

  5. #5
    Join Date
    Oct 2007
    Location
    Madison, WI
    Posts
    11,949

    Default

    Thanks, Dave.

    I tried several more times. One of these times I may have reproduced these results (or, in my many tests, made a mistake and accidentally called on two equal files ). I'll open a tracker entry to see if we can investigate. Did you use the exact command lines from the first post to generate the sample files?
    Aaron P Scooter Software

  6. #6
    Join Date
    Dec 2007
    Location
    U.S. East coast
    Posts
    303

    Default

    I just repeated the test, using these commands:

    Code:
    cd /tmp
    dd if=/dev/zero bs=1M seek=32 count=0 of=bc4test.a
    echo a >> bc4test.a
    dd if=/dev/zero bs=1M seek=32 count=0 of=bc4test.b
    echo b >> bc4test.b
    bcompare bc4test.a bc4test.b &
    BC reports "Binary same".

    The last byte displayed has offset 012AFFFF (decimal 19595263).

    I'm attaching a .zip containing the two test files.
    Attached Files Attached Files

  7. #7
    Join Date
    Oct 2007
    Location
    Madison, WI
    Posts
    11,949

    Default

    Thanks. I'm not seeing this 100% of the time on different systems, but I have managed to make it happen a few times on Ubuntu 12.04. Hopefully we can track this down and figure out what is happening here.
    Aaron P Scooter Software

  8. #8
    Join Date
    Dec 2007
    Location
    U.S. East coast
    Posts
    303

    Default

    Any progress on this? It's a concern for me that BC could report different files as being identical.

  9. #9
    Join Date
    Oct 2007
    Location
    Madison, WI
    Posts
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    Default

    We're still investigating. Our main Linux developer was mid-project on a few things, but he's wrapped up enough to help dig into this.
    Aaron P Scooter Software

  10. #10
    Join Date
    Dec 2007
    Location
    U.S. East coast
    Posts
    303

    Default

    I don't like pestering you about this, but I think it's a serious problem. It's worse than crashing. If BC crashes, at least you know the comparison failed. In this case, BC is providing bad information.

    So, any progress?

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