Author: Armin Rigo <ar...@tunes.org> Branch: Changeset: r78355:d3d07e983854 Date: 2015-06-30 08:52 +0200 http://bitbucket.org/pypy/pypy/changeset/d3d07e983854/
Log: Mention issue #2030 in cpython_differences diff --git a/pypy/doc/cpython_differences.rst b/pypy/doc/cpython_differences.rst --- a/pypy/doc/cpython_differences.rst +++ b/pypy/doc/cpython_differences.rst @@ -135,7 +135,7 @@ Here are some more technical details. This issue affects the precise time at which ``__del__`` methods are called, which is not reliable in PyPy (nor Jython nor IronPython). It also means that -weak references may stay alive for a bit longer than expected. This +**weak references** may stay alive for a bit longer than expected. This makes "weak proxies" (as returned by ``weakref.proxy()``) somewhat less useful: they will appear to stay alive for a bit longer in PyPy, and suddenly they will really be dead, raising a ``ReferenceError`` on the @@ -143,6 +143,24 @@ ``ReferenceError`` at any place that uses them. (Or, better yet, don't use ``weakref.proxy()`` at all; use ``weakref.ref()``.) +Note a detail in the `documentation for weakref callbacks`__: + + If callback is provided and not None, *and the returned weakref + object is still alive,* the callback will be called when the object + is about to be finalized. + +There are cases where, due to CPython's refcount semantics, a weakref +dies immediately before or after the objects it points to (typically +with some circular reference). If it happens to die just after, then +the callback will be invoked. In a similar case in PyPy, both the +object and the weakref will be considered as dead at the same time, +and the callback will not be invoked. (Issue `#2030`__) + +.. __: https://docs.python.org/2/library/weakref.html +.. __: https://bitbucket.org/pypy/pypy/issue/2030/ + +--------------------------------- + There are a few extra implications from the difference in the GC. Most notably, if an object has a ``__del__``, the ``__del__`` is never called more than once in PyPy; but CPython will call the same ``__del__`` several times _______________________________________________ pypy-commit mailing list pypy-commit@python.org https://mail.python.org/mailman/listinfo/pypy-commit
