# Boost.Python TODO list

copyright: | Copyright David Abrahams 2003. Use, modification, and distribution are subject to the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

Outline

- Class Support
  - Base Class for Virtual Function Callback Wrappers
- Miscellaneous
  - Support for Enums with Duplicate Values
- Functions
  - Wrapping Function Objects
  - "Best Match" Overload Resolution
- Type Converters
  - Lvalue conversions from non-const `PyTypeObject*`s
  - Converter Scoping
  - `FILE*` conversions
  - `void*` conversions
  - Post-Call Actions
  - `PyUnicode` Support
  - Ownership Metadata
- Documentation
  - Builtin Converters
  - Internals
- Large Scale
  - Full Threading Support
  - Langbinding
  - Refactoring and Reorganization
  - NumArray Support Enhancements
  - `PyFinalize` Safety

# Class Support

## Base Class for Virtual Function Callback Wrappers

- http://aspn.activestate.com/ASPN/Mail/Message/c++-sig/1456023 (bottom of message)
- http://mail.python.org/pipermail/c++-sig/2003-August/005297.html (search for `VirtualDispatcher`) describes how callback classes can swap ownership relationship with their Python wrappers.
- http://aspn.activestate.com/ASPN/Mail/Message/c++-sig/1860301 describes how this can also be used to considerably simplify callback classes, solve some "dangling reference" problems, and optimize the calling of non-overridden virtual functions.

# Miscellaneous

## Support for Enums with Duplicate Values

> Scott Snyder provided a patch; Dave was dissatisfied for some reason, but maybe it should just be applied if no further action occurs http://aspn.activestate.com/ASPN/Mail/Message/1824616.

# Functions

## Wrapping Function Objects

> It should be possible to wrap classes which support `operator()` as Python methods.

> http://mail.python.org/pipermail/c++-sig/2003-August/005184.html

## "Best Match" Overload Resolution

> Overload resolution currently depends on the order in which `def` calls are made (preferring later overloads). This should be changed so that the best-matching overload is always selected. This may await Langbinding integration, since the technology is already in Luabind.

# Type Converters

## Lvalue conversions from non-const `PyTypeObject*`s

> http://aspn.activestate.com/ASPN/Mail/Message/C++-sig/1662717

## Converter Scoping

> http://article.gmane.org/gmane.comp.python.c++/2044

> If this gets done at all, it is going to happen in conjunction with Luabind integration.

## `FILE*` conversions

> http://aspn.activestate.com/ASPN/Mail/Message/1411366

## `void*` conversions

> Pointers to cv `void` should be able to be passed and returned as opaque values.

## Post-Call Actions

> From-Python converters should be passed an extra reference to a chain of post-call actions in the Policies object, where they can register an additional action. See the end of http://aspn.activestate.com/ASPN/Mail/Message/C++-sig/1755435

## `PyUnicode` Support

> Review and possibly incorporate changes from Lijun Qin at http://aspn.activestate.com/ASPN/Mail/Message/C++-sig/1771145

## Ownership Metadata

> In the thread at http://aspn.activestate.com/ASPN/Mail/Message/c++-sig/1860301, Niall Douglas describes an idea for solving some "false" dangling pointer/reference return errors by attaching data about objects which lets the framework determine that the reference count on an object doesn't tell us anything about the lifetime of its data.

# Documentation

## Builtin Converters

> Builtin correspondences between builtiin Python types and C++ types need to be documented

## Internals

> The structure of the framework needs to get documented; Brett Calcott has promised to turn this document into something fit for users

# Large Scale

## Full Threading Support

> Various people have proposed patches to improve threading support in Boost.Python: see the thread at http://aspn.activestate.com/ASPN/Mail/Message/1826544 and http://aspn.activestate.com/ASPN/Mail/Message/1865842 for some examples. The only problem is that these are incomplete solutions and verifying that we do have a complete solution is going to take some time and attention.

## Langbinding

> This project to generalizes Boost.Python to work for other languages, initially Lua. See discussions at http://lists.sourceforge.net/lists/listinfo/boost-langbinding

## Refactoring and Reorganization

> http://aspn.activestate.com/ASPN/Mail/Message/c++-sig/1673338

## NumArray Support Enhancements

> Consider integrating the enhancements described in http://aspn.activestate.com/ASPN/Mail/Message/C++-sig/1757092

## `PyFinalize` Safety

> Currently Boost.Python has several global (or function-static) objects whose existence keeps reference counts from dropping to zero until the Boost.Python shared object is unloaded. This can cause a crash because when the reference counts do go to zero, there's no interpreter. In order to make it safe to call `PyFinalize()` we must register an `atexit` routine which destroys these objects and releases all Python reference counts so that Python can clean them up while there's still an interpreter. Dirk Gerrits has promised to do this job.