weakrefs to resolve cyclical dependencies that prevent garbage collec…

…tion

sh.py

@@ -80,6 +80,7 @@
 import resource
 from collections import deque
 import logging
+import weakref
 
 
 # this is ugly, but we've added a module-level logging kill switch.  the reason
@@ -1002,14 +1003,14 @@ class NoStdinData(Exception): pass
 class StreamWriter(object):
     def __init__(self, name, process, stream, stdin, bufsize):
         self.name = name
-        self.process = process
+        self.process = weakref.ref(process)
         self.stream = stream
         self.stdin = stdin
 
         self.log = logging.getLogger(repr(self))
 
 
-        self.stream_bufferer = StreamBufferer(self.process.call_args["encoding"],
+        self.stream_bufferer = StreamBufferer(self.process().call_args["encoding"],
             bufsize)
 
         # determine buffering for reading from the input we set for stdin
@@ -1050,7 +1051,7 @@ def __init__(self, name, process, stream, stdin, bufsize):
 
 
     def __repr__(self):
-        return "<StreamWriter %s for %r>" % (self.name, self.process)
+        return "<StreamWriter %s for %r>" % (self.name, self.process())
 
     def fileno(self):
         return self.stream
@@ -1087,7 +1088,7 @@ def write(self):
         except DoneReadingStdin:
             if logging_enabled: self.log.debug("done reading")
 
-            if self.process.call_args["tty_in"]:
+            if self.process().call_args["tty_in"]:
                 # EOF time
                 try: char = termios.tcgetattr(self.stream)[6][termios.VEOF]
                 except: char = chr(4).encode()
@@ -1101,7 +1102,7 @@ def write(self):
 
         # if we're not bytes, make us bytes
         if IS_PY3 and hasattr(chunk, "encode"):
-            chunk = chunk.encode(self.process.call_args["encoding"])
+            chunk = chunk.encode(self.process().call_args["encoding"])
 
         for chunk in self.stream_bufferer.process(chunk):
             if logging_enabled: self.log.debug("got chunk size %d: %r", len(chunk), chunk[:30])
@@ -1120,25 +1121,26 @@ def close(self):
         if logging_enabled: self.log.debug("got chunk size %d to flush: %r", len(chunk), chunk[:30])
         try:
             if chunk: os.write(self.stream, chunk)
-            if not self.process.call_args["tty_in"]:
+            if not self.process().call_args["tty_in"]:
                 if logging_enabled: self.log.debug("we used a TTY, so closing the stream")
                 os.close(self.stream)
         except OSError: pass
 
 
 
 class StreamReader(object):
-
     def __init__(self, name, process, stream, handler, buffer, bufsize, pipe_queue=None):
         self.name = name
-        self.process = process
+        self.process = weakref.ref(process)
         self.stream = stream
         self.buffer = buffer
-        self.pipe_queue = pipe_queue
+
+        self.pipe_queue = None
+        if pipe_queue: self.pipe_queue = weakref.ref(pipe_queue)
 
         self.log = logging.getLogger(repr(self))
 
-        self.stream_bufferer = StreamBufferer(self.process.call_args["encoding"],
+        self.stream_bufferer = StreamBufferer(self.process().call_args["encoding"],
             bufsize)
 
         # determine buffering
@@ -1183,24 +1185,28 @@ def __init__(self, name, process, stream, handler, buffer, bufsize, pipe_queue=N
 
 
             self.handler_args = ()
-            if num_args == implied_arg + 2: self.handler_args = (self.process.stdin,)
-            elif num_args == implied_arg + 3: self.handler_args = (self.process.stdin, self.process)
+            if num_args == implied_arg + 2:
+                self.handler_args = (self.process().stdin,)
+            elif num_args == implied_arg + 3:
+                self.handler_args = (self.process().stdin, self.process())
+
 
     def fileno(self):
         return self.stream
 
     def __repr__(self):
-        return "<StreamReader %s for %r>" % (self.name, self.process)
+        return "<StreamReader %s for %r>" % (self.name, self.process())
 
     def close(self):
         chunk = self.stream_bufferer.flush()
-        if logging_enabled: self.log.debug("got chunk size %d to flush: %r", len(chunk), chunk[:30])
+        if logging_enabled: self.log.debug("got chunk size %d to flush: %r",
+            len(chunk), chunk[:30])
         if chunk: self.write_chunk(chunk)
 
         if self.handler_type == "fd" and hasattr(self.handler, "close"):
             self.handler.flush()
 
-        if self.pipe_queue: self.pipe_queue.put(None)
+        if self.pipe_queue: self.pipe_queue().put(None)
         try: os.close(self.stream)
         except OSError: pass
 
@@ -1211,20 +1217,20 @@ def write_chunk(self, chunk):
         if self.handler_type == "fn" and not self.should_quit:
             # try to use the encoding first, if that doesn't work, send
             # the bytes
-            try: to_handler = chunk.decode(self.process.call_args["encoding"])
+            try: to_handler = chunk.decode(self.process().call_args["encoding"])
             except UnicodeDecodeError: to_handler = chunk
             self.should_quit = self.handler(to_handler, *self.handler_args)
 
         elif self.handler_type == "stringio":
-            self.handler.write(chunk.decode(self.process.call_args["encoding"]))
+            self.handler.write(chunk.decode(self.process().call_args["encoding"]))
 
         elif self.handler_type in ("cstringio", "fd"):
             self.handler.write(chunk)
 
 
         if self.pipe_queue:
             if logging_enabled: self.log.debug("putting chunk onto pipe: %r", chunk[:30])
-            self.pipe_queue.put(chunk)
+            self.pipe_queue().put(chunk)
         self.buffer.append(chunk)