Detect failures to explicitly close mmaps in py3 too

[bup.git] / lib / bup / io.py

diff --git a/lib/bup/io.py b/lib/bup/io.py
index 512d36434ed57e800f3b1f647a8982a909ec6ac2..a384f1007e5d5f0452d646633a658b01b1dad9f0 100644 (file)
--- a/lib/bup/io.py
+++ b/lib/bup/io.py
@@ -1,7 +1,9 @@
 
 from __future__ import absolute_import, print_function
+import mmap as py_mmap
 
 from bup import compat
+from bup.compat import pending_raise
 
 
 if compat.py_maj > 2:
@@ -20,3 +22,47 @@ else:
         """Return a string representation of a path."""
         # FIXME: configurability (might git-config quotePath be involved?)
         return x
+
+
+assert not hasattr(py_mmap.mmap, '__del__')
+if hasattr(py_mmap.mmap, '__enter__'):
+    assert hasattr(py_mmap.mmap, '__exit__')
+
+class mmap(py_mmap.mmap):
+    '''mmap.mmap wrapper that detects and complains about any instances
+    that aren't explicitly closed.
+
+    '''
+
+    def __init__(self, *args, **kwargs):
+        self._bup_closed = True
+        # Silence deprecation warnings.  mmap's current parent is
+        # object, which accepts no params and as of at least 2.7
+        # warns about them.
+        if py_mmap.mmap.__init__ is not object.__init__:
+            super(mmap, self).__init__(self, *args, **kwargs)
+        self._bup_closed = False
+
+    def close(self):
+        self._bup_closed = True
+        super(mmap, self).close()
+
+    if hasattr(py_mmap.mmap, '__enter__'):
+        def __enter__(self):
+            super(mmap, self).__enter__()
+            return self
+        def __exit__(self, type, value, traceback):
+            # Don't call self.close() when the parent has its own __exit__;
+            # defer to it.
+            self._bup_closed = True
+            result = super(mmap, self).__exit__(type, value, traceback)
+            return result
+    else:
+        def __enter__(self):
+            return self
+        def __exit__(self, type, value, traceback):
+            with pending_raise(value, rethrow=False):
+                self.close()
+
+    def __del__(self):
+        assert self._bup_closed