SIGWINCH may not exist, even on non-Win32 platforms

[Matt Nordhoff]

bzrlib.osutils.watch_sigwinch() assumes that SIGWINCH exists on all non-Win32 platforms, even though this may not be the case.

Specifically, a user in #bzr had issues because an old MacPorts build of Python 2.4.6 lacks SIGWINCH. Switching to OS X's 2.6.1 build fixed the problem.

It should be simple enough to just use getattr to check if it's available instead of checking the platform, unless signal does something bizarre?

[Martin Packman (gz)]

I've a branch with a fix for this, but the code has been moved more
than once since it landed so repeated conflicts have got in the way of
getting it landed.

The change started as the below, but any similar alteration to the
conditional should work:

=== modified file 'bzrlib/osutils.py'
--- old/bzrlib/osutils.py 2009-12-17 22:16:59 +0000
+++ new/bzrlib/osutils.py 2009-12-17 22:17:42 +0000
@@ -1477,11 +1477,7 @@
     if width is not None:
         os.environ['COLUMNS'] = str(width)

-if sys.platform == 'win32':
- # Martin (gz) mentioned WINDOW_BUFFER_SIZE_RECORD from ReadConsoleInput but
- # I've no idea how to plug that in the current design -- vila 20091216
- pass
-else:
+if os.name == "posix" and getattr(signal, "SIGWINCH", None) is not None:
     signal.signal(signal.SIGWINCH, _terminal_size_changed)

[Martin Packman (gz)]

Should be resolved in r5180.

[Vincent Ladeuil (vila)]

@gz: we don't use fix committed anymore, we wait for the fix to land in either a stable branch or bzr.dev and set the milestone accordingly.

In retrospect, it's too bad we didn't put a NEWS entry to refer to this bug...