2011/5/18 Sven Severus: > let me report a strange behaviour with Cygwin Perl (I'm using cygwin1.dll > 1.7.9-1, full installation 2 weeks ago). > > File foo.h is an ordinary text file, all lines are terminated with DOS > style line endings <cr> <lf> (hex: 0d 0a). > It is located in a directory with textmode mounting in cygwin. > One <cr> <lf> sequence of foo.h is split by a 4096 byte boundary within > the file: "od -c -Ax foo.h" shows a <cr> (='\r') at byte offset 4095 > (0xfff) > and a <lf> (='\n') at offset 4096 (0x1000): > ... > 000ff0 / / / / / / \r \n / / X X X X X \r > 001000 \n / / \r \n / / \r \n > 001009 > > Now I issued the command "perl -pe 's/12345/54321/' foo.h >foomod.h" > to produce foomod.h, located in the same directory as foo.h, thus with > textmode mounting too. > When I examined the result, I noticed that foomod.h was one byte bigger > then foo.h. I expected identical size, and "od -c -Ax foomod.h" reports: > ... > 000ff0 / / / / / / \r \n / / X X X X X \r > 001000 \r \n / / \r \n / / \r \n > 00100a > > Ups! The original <cr> <lf> sequence starting at offset 4095 (0xfff) > became a three character sequence <cr> <cr> <lf>! The <cr> is duplicated! > > In other files created by Perl with output redirection I observed this > behaviour with every <cr> <lf> line ending, that is split by a 4096 byte > boundary (even multiple times in one output file). Line endings not > split by a 4096 byte boundary do not show this behaviour. > > The behaviour does not occur, when the destination file is located > in a directory with binmode mounting. It does not occur either, when > I use sed instead of Perl ("sed -e 's/12345/54321/' foo.h >foomod.h"), > so I think the problem is specific to Cygwin Perl, not to Cygwin in > general. > > I this a bug of the output buffering mechanism of Cygwin Perl? > Or do I anything wrong? > Any answer is highly appreciated. Thanks in advance.
Yes, this looks like a PerlIO buffering bug for MSWin32 and cygwin. The last char of the buffer is not stored when checking the first char of the new buffer. I think first we have to provide a sample test case to perl core. -- Reini Urban http://phpwiki.org/ http://murbreak.at/ -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple