Greetings, Thomas Wolff! > Am 19.02.2015 um 10:51 schrieb Corinna Vinschen: >> On Feb 18 22:08, Lasse Collin wrote: >>> (Please Cc me when replying, I'm not subscribed to the list.) >>> >>> Hi! >>> >>> I suspect that there is a bug in Cygwin: >>> >>> 1. Create a pipe with both ends in blocking mode (O_NONBLOCK >>> is not set). >>> 2. The writer sets its end to non-blocking mode. >>> 3. The writer writes to the pipe. >>> 4. The writer restores its end of the pipe to blocking mode >>> before the reader has read anything from the pipe. >>> 5. The writer closes its end of the pipe. >>> 6. The reader reads from the pipe in blocking mode. The last >>> bytes written by the writer never appear at the reader, >>> thus data is silently lost. >>> >>> Omitting the step 4 above makes the problem go away. >> I can imagine. A few years back, when changing the pipe code to >> using overlapped IO, we stumbled over a problem in Windows. When >> closing an overlapped pipe while I/O is still ongoing, Windows >> simply destroys the pipe buffers without flushing the data to the >> reader. This is not much of a problem for blocking IO, but it >> obviously is for non-blocking. >> >> The workaround for this behaviour is this: If the pipe is closed, and >> this is the writing side of a nonblocking pipe, a background thread gets >> started which keeps the overlapped structure open and continues to wait >> for IO completion (i.e. the data has been sent to the reader). >> >> However, if you switch back to blocking before closing the pipe, the >> aforementioned mechanism does not kick in. > Could not "switching back to blocking" simply be handled like closing as > far as the waiting is concerned, > thus effectively flushing the pipe buffer?
You can't "just flush" it, if the receiving end isn't reading from it. -- WBR, Andrey Repin (anrdae...@yandex.ru) 20.02.2015, <02:46> Sorry for my terrible english... -- 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
