Message-Id: <588311DB-B528-4386-8C6D-A14A37F85737@free.fr>
From: Denis Excoffier <Denis DOT Excoffier AT free DOT fr>
To: cygwin AT cygwin DOT com
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Subject: Re: enlarge MAXSYMLINKS
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Date: Tue, 10 Mar 2009 19:05:17 +0100
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Again about symbolic links, here is some new inputs:

1) MAXSYMLINKS is no longer used in modern Cygwin's;
    indeed, cygwin-1.5.25-15 uses MAX_LINK_DEPTH and
    cygwin-1.7.0-42 uses SYMLOOP_MAX; both are set to 10
    (in ./winsup/cygwin/path.h for 1.5 and in
    ./winsup/cygwin/include/limits.h for 1.7)

2) whether the filesystem is NTFS or not makes no difference;
    whether the symlinks are created using winsymlinks or nowinsymlinks
    makes no difference

3) the only clean way to make cygwin1.dll accept a chain of 32 symlinks
    (instead of 10) is through recompilation

4) for those interested in not-so-clean items, the following may also  
work
    - for 1.5.25-15 (this one i have tested)
      - cd /usr/bin
      - cat cygwin1.dll | perl -pi -e 's|\203\275\224\371\377\377\012| 
\203\275\224\371\377\377\040|' > cygwin1.dll.new
      - check that cksum before is 3685478250
      - check that cksum after is 3302069714
      - set the appropriate permissions/owners/groups etc. on  
cygwin1.dll.new
      - from outside Cygwin (eg. from Windows):
        - rename cygwin1.dll into cygwin1.dll.old
        - rename cygwin1.dll.new into cygwin1.dll
    - for 1.7.0-42 (this one i have not tested, please report if fails)
      - same as before, with the -e expression replaced by
        -e 's|\203\275\344\355\377\377\013| 
\203\275\344\355\377\377\041|'
    - how you can find these strings yourself:
      1) either
         - objdump -d cygwin1.dll
         - look for path_conv::check(...)
         - search into those 1000 lines, trying to make the names to  
match
         - try
      2) or
         - recompile with SYMLOOP_MAX set to 10 (result1)
         - recompile with SYMLOOP_MAX set to 10 (result2)
         - recompile with SYMLOOP_MAX set to 32 (result3)
         - compare result1 and result2 to discover the impact of current
           time in the result
         - compare result1 and result3 and eliminate the impact of
           current time
         - (make sure that compilation options are the same as  
originally)

5) i would also make the following suggestions:

    1) to enhance cygcheck to report whether a given symlink is
       implemented as a Windows'shortcut or as an adhoc Cygwin symlink
       (although this can be seen easily from outside Windows)

    2) to use "#define SYMLOOP_MAX 32" in future Cygwin-1.7


Hope this helps,

Denis Excoffier.


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