Note C API incompatibilities
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@ -1453,6 +1453,23 @@ actually drop when you delete them, and the memory may be returned to
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the operating system. (Implemented by Evan Jones, and reworked by Tim
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Peters.)
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Note that this change means extension modules need to be more careful
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with how they allocate memory. Python's API has a number of different
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functions for allocating memory that are grouped into families. For
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example, \cfunction{PyMem_Malloc()}, \cfunction{PyMem_Realloc()}, and
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\cfunction{PyMem_Free()} are one family that allocates raw memory,
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while \cfunction{PyObject_Malloc()}, \cfunction{PyObject_Realloc()},
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and \cfunction{PyObject_Free()} are another family that's supposed to
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be used for creating Python objects.
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Previously these different families all reduced to the platform's
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\cfunction{malloc()} and \cfunction{free()} functions. This meant
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it didn't matter if you got things wrong and allocated memory with the
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\cfunction{PyMem} function but freed it with the \cfunction{PyObject}
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function. With the obmalloc change, these families now do different
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things, and mismatches will probably result in a segfault. You should
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carefully test your C extension modules with Python 2.5.
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\item Coverity, a company that markets a source code analysis tool
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called Prevent, provided the results of their examination of the Python
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source code. The analysis found a number of refcounting bugs, often
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@ -1472,6 +1489,21 @@ changes to your code:
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\item The \module{pickle} module no longer uses the deprecated \var{bin} parameter.
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\item C API: Many functions now use \ctype{Py_ssize_t}
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instead of \ctype{int} to allow processing more data
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on 64-bit machines. Extension code may need to make
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the same change to avoid warnings and to support 64-bit machines.
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See the earlier
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section~ref{section-353} for a discussion of this change.
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\item C API:
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The obmalloc changes mean that
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you must be careful to not mix usage
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of the \cfunction{PyMem_*()} and \cfunction{PyObject_*()}
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families of functions. Memory allocated with
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one family's \cfunction{*_Malloc()} must be
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freed with the corresponding family's \cfunction{*_Free()} function.
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\end{itemize}
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