On Dec 14 11:50, Corinna Vinschen wrote: > On Dec 13 19:36, Eric Blake wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > > Hash: SHA1 > > > > According to Jack Brennen on 12/13/2007 6:34 PM: > > > sh-3.2$ echo ABCDEFGHIJKLMNOPQRST > foo.txt > > > sh-3.2$ cmd /c echo UVWXYZ >> foo.txt > > > sh-3.2$ cat foo.txt > > > UVWXYZ > > > IJKLMNOPQRST > > > > This issue was discussed on the lists in May: > > > > http://thread.gmane.org/gmane.os.cygwin/89327/focus=89411 > > > > Cygwin 1.5.24 was incorrectly positioning fd's opened in append mode to > > the last byte just before exec'ing a child process, rather than leaving > > the position untouched (note that POSIX requires > > open(O_RDWR|O_APPEND)/lseek to always be at position 0, but > > fopen("a+")/ftell can be either 0 [as on Linux] or the end of the file [as > > on BSD] - cygwin currently uses the Linux approach). > > > > But it looks like this means that Windows programs are too stupid to > > realize that they are being handed a file opened in append mode [...] > > Even though it sounds nice to blame Windows, the blame is on Cygwin > entirely here. The problem with O_APPEND mode is that you can switch > a file descriptor to and from append mode at will using fcntl. This > functionality doesn't exist in the Win32 API. You either open the > file handle in append mode or not, but you can't switch it back and > forth. > > For that reason, the file is always opened in generic write mode in > Cygwin. Append mode is emulated in the write() call by seeking to > the end of the file before writing (in 1.5.x) or by using a feature > of the native NT ZwWriteFile call (in 1.7.x). > > At this point we have three choices: > [...]
Scratch that, I implemented the forth choice. Eric's point > Maybe it is worth teaching cygwin's exec code that fd's in append mode > must be repositioned to the end if the child about to be spawned is a > non-cygwin program? was right. I implemented this now, for 1.5.25 as well as for the main trunk. I will look into implementing this in a more transparent way for 1.7.x, though. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Project Co-Leader cygwin AT cygwin DOT com Red Hat -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/
