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From: Eric Blake <ebb9 AT byu DOT net>
Subject:  Re: [1.7] getgroups regression?
Date: Fri, 4 Dec 2009 22:48:35 +0000 (UTC)
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Eric Blake <ebb9 <at> byu.net> writes:

> 
> On the same machine, I see:
> 
> cygwin-1.5$ id -G | wc
>       1      24     136
> 
> cygwin-1.7$ id -G | wc
>       1      46     264
> cygwin-1.7$ printf %s\\n `id -G` | sort -u | wc
>      24      24     136
> 
> In other words, under cygwin 1.7, the last 22 entries are placed in the 
> getgroups results twice.

On further review, I found my 1.7 /etc/group was more than twice the size of 
the 1.5 version; and all of that bulk came from duplicated entries.

$ ls -l /etc/group.old /etc/group
-rwxr-xr--+ 1 eblake Domain Users  75790 2008-12-15 10:56 /etc/group.old*
-rwxr-xr--  1 eblake Domain Users 151559 2009-05-11 07:51 /etc/group*
$ cmp <(sort -u /etc/group.old) <(sort -u /etc/group); echo $?
0

So, cygwin 1.7 getgroups was listing duplicates because my /etc/group had 
duplicates.  Remove the duplicates, and now I get the same results in id for 
1.7 as I did for 1.5.

But that still makes me wonder - is there anything we are doing in a typical 
install that might be accidentally inserting duplicate entries into /etc/group, 
or is this something I managed to fubar all by myself way back when I first 
created my side-by-side 1.5/1.7 installation (back before the transition was as 
smooth as it is now)?

Meanwhile, is sorting and/or pruning duplicate getgroups results something that 
cygwin should consider doing?  POSIX is explicit that the result is a 
mathematical set, and that two processes can have the same set membership but 
different orders based on the sequence of events that created those two 
processes.  But will Linux ever list a duplicate, even if duplicates appear 
in /etc/group?

-- 
Eric Blake




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