hook: forcibly flush stderr for Windows test stability There are a handful of SSH related test failures on Windows. --- c:/Users/Matt/Projects/hg/tests/test-bundle2-exchange.t +++ c:/Users/Matt/Projects/hg/tests/test-bundle2-exchange.t.err @@ -305,16 +305,16 @@ remote: added 1 changesets with 1 changes to 1 files remote: 1 new obsolescence markers updating bookmark book_5fdd + pre-close-tip:02de42196ebe draft book_02de + postclose-tip:02de42196ebe draft book_02de + txnclose hook: HG_SOURCE=push-response HG_TXNNAME=push-response + ssh://user@dummy/other HG_URL=ssh://user@dummy/other remote: pre-close-tip:5fddd98957c8 draft book_5fdd remote: pushkey: lock state after "bookmarks" remote: lock: free remote: wlock: free remote: postclose-tip:5fddd98957c8 draft book_5fdd remote: txnclose hook: (env vars truncated) - pre-close-tip:02de42196ebe draft book_02de - postclose-tip:02de42196ebe draft book_02de - txnclose hook: HG_SOURCE=push-response HG_TXNNAME=push-response - ssh://user@dummy/other HG_URL=ssh://user@dummy/other $ hg -R other log -G o 6:5fddd98957c8 draft Nicolas Dumazet <...> book_5fdd C | --- c:/Users/Matt/Projects/hg/tests/test-ssh.t +++ c:/Users/Matt/Projects/hg/tests/test-ssh.t.err @@ -438,12 +438,12 @@ $ hg push pushing to ssh://user@dummy/remote searching for changes + local stdout remote: adding changesets remote: adding manifests remote: adding file changes remote: added 1 changesets with 1 changes to 1 files - remote: KABOOM - local stdout + remote: KABOOM\r (esc) $ cd .. What is happening is that no data is available in 'sshpeer.pipee' while the command is executing. As the command completes, local output is printed, and then sshpeer.cleanup() is called. When it calls 'self.pipeo.close()', the child process is shutdown, flushing stderr. As an experiment, I printed a line to stdout and another to stderr instead this flush(). The stdout data was immediately available to the hg client, and none of the stderr data was until the child exited. At that point, pipee has all of the buffered data, and it is read out and printed before the pipe is closed in sshpeer.cleanup(). This is probably a known issue, since ui.write_err() mentions that stderr may be buffered, and also flushes stderr. It would be nice if there was a more general fix (there is one more test that fails), but I'm not sure what it is. I've seen (ancient) references [1] to setvbuf() "crashing spectacularly" on some systems if any I/O has been done already, so it seems worth avoiding. https://sourceware.org/ml/gdb-patches/2013-08/msg00422.html [1] https://groups.google.com/forum/#!msg/comp.lang.python/JT8LiYzYDEY/Qg9d1HwyjScJ