Re: bug #41707: RCS 5.8 file corruption when using file descriptor IO for large files

[Thien-Thi Nguyen]

() Achim Gratz <address@hidden>
() Thu, 19 Jun 2014 23:30:34 +0200

   As described in

   https://cygwin.com/ml/cygwin/2012-06/msg00334.html
   https://cygwin.com/ml/cygwin/2012-09/msg00331.html

   and demonstrated with

   https://cygwin.com/ml/cygwin/2013-10/msg00086.html

   the STDIO code path fails for work files above a certain size on
   Cygwin.  Based on the analysis of how the breakage occurs I've
   developed the following patch for your consideration:

Thanks for the patch, and the analysis, too.  The latter i could
not / cannot do since i don't have access to such a platform.  As
for the patch (and because of the lack of platform access), i
request your help to proceed as follows:

- I have rewritten the test, attached here, to be more idiomatic.

t820
Description: Binary data

  The first step is to check that this test fails for you when
  unpatched, and passes when patched.  Could you please confirm?
  (NB the ??? re ‘need_subdir’.)  The "maybe" in the description
  is because there was no way for 5.7 to force STDIO operation,
  so the problem might have been latent at that time.

- I'm wary of adding the close/re-open sequence unconditionally and
  wonder if there is a way to detect systems that misbehave thusly
  with a short C program (or better yet, sequence of shell
  commands) to be run by the configure script.  What do you think?

- etc

It's probably best to worry about "etc" after we surmount these
first two steps.  I understand that there is a difference between
GNU/Linux (say) and Cygwin, but i don't understand (yet) if that
difference is legitimate (i.e., allowed by POSIX or other relevant
standards).  What do you suggest i read to understand the analysis
linked in the URL above?
  
-- 
Thien-Thi Nguyen
   GPG key: 4C807502
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