swig/TODO

SWIG TO-DO

Release: SWIG-1.3.36

-----------------------------------------------------------------------------

****    = High Priority
***     = Implement if possible.
**      = Will implement if time.
*       = Implement if bored (or deemed necessary).

defer   = Implement in next version

CORE:

****   Add support for nested classes.   The type system should be
defer  ready to go.  The primary obstacle lies in the target language
       modules (which were never programmed with nested classes in
       mind).  There are also issues with nested C structures.  For
       example:

             struct Foo {
                 struct {
                     int x,y;
                 } z;
             };

       This is one of the last remaining "hard" problems in the SWIG
       core, but it is important that we solve it.

***    "Nested" typemaps. The basic idea is similar to allowing one to 
       use $descriptor(T) for any T, rather than just $descriptor
       for the type currently being typemapped.

       In short (ha!), given a previously defined typemap:

       %typemap(in) Foo {
           // whatever it takes to initialize $1 from $input
       }

       it would be possible to inline its code inside another typemap. 
       While the syntax is still to be defined, the use would be
       along the lines of:

       template <class T> class vector {
           %typemap(in) vector<T> {
               ...
               for (int i=0; i<N; i++) {
                   PyObject* x = ... // i-th element
                   $typemap(in, T, x, $1[i]);
               }
               ...
           }
           ...
       }

       i.e., when $typemap(in,Foo,x,y) is encountered, it will
       be replaced by the code for %typemap(in) Foo; in the latter,
       x will be replaced for $input and y will be replaced for $1. 
       As in the case above, x and y themselves might need to be 
       expanded before or after being substituted in the typemap code.
       Also, $typemap(what,Foo,x,y,z,...) will be used in case of 
       multi-arguments typemaps. The same will hold for "out" typemaps
       and all the others.

       Comment by mkoeppe:  

	  I think we need to be careful to keep the syntax readable.
	  I would like to get a syntax that is close to that of
	  typemap definitions.  So consider this typemap:

		 %typemap(in) int { ... }

	  I would like to refer to this typemap like this:

		 $typemap(in, input=x) int = foo;

	  Here $input would be replaced by the given keyword argument
	  x, and $1 would be replaced by foo.

	  This syntax would extend easily to multi-typemaps:

		 %typemap(in) ( int FIRST, double SECOND ) { ... }

	      -> $typemap(in, input=x) 
	      	    ( int FIRST = foo, double SECOND = bar );

	  The advantage of this syntax would be that the formal
	  arguments (int FIRST, double SECOND) are close to the
	  actual arguments (foo, bar).

	Comment by beazley

               $typemap(in, input=x) int = foo;

        is a little bit hard to parse in terms of variable substitution.
        I'm considering something like this:

               $typemap(in,1=int foo, input=x)

       Note: This is partially implemented in the new Unified Typemap
       Library(python,tcl,ruby and perl) via %fragments and the
       SWIG_From/SWIG_AsVal methdos.

***    Implement $fail special variable substitution in wrappers. Used
       to properly transfer control out of a wrapper function while
       reclaiming resources.

       Note: Implemented in languages that uses the UTL via the
       'SWIG_fail' macro.

***    Rewrite declaration annotation to better unify %rename and related
       directives.  Add a selector mechanism that allows specific parse tree
       nodes to be identified.  For example:

             %feature("foo", nodetype="class") Foo { ... some code ... };

       Consider use of wildcards.   Namespace/nested scope support in
       %feature is currently weak.  It works, but is fragile.  Consider
       an implementation that is better integrated with symbol table
       management.  Continue to consolidate SWIG directives to %feature.

       Note: Initial implementation in the %rename directive.

***    Add more intelligent information related to object ownership.
       SWIG should be able to automatically strip ownership from
       objects when they are assigned to pointer variables and structure
       members as well as stored in a container (i.e., an array of pointers).

       [ Partially finished for Ruby/Perl/Tcl/Python. ]

**     Restoration of the documentation system.
       [ Partially done for Python. ]
              

**     Restoration of Objective-C support.

**     Unification of symbol tables and type system scopes.  In a sense
       they capture the same information so it is not necessary to have
       both.  The existence of two symbol management systems is mostly
       historical.

Build
-----

Library
-------

****   Add more support for the C++ standard library.  std::complex and other
       core datatypes.   Refine support for STL vector.   Add more STL objects.

       [ Partially finished for Python. ]

****   Continue to expand the set of recognized typemaps.

Windows
-------

All language modules
--------------------

Python
------

***    Ability to wrap certain classes as Python built-in types.

Perl
----

****   Rewrite runtime pointer type checking to better integrate
       shadow classes.   Creation of shadow classes should be done
       in C instead of Perl.   This will fix a number of problems
       related to typemaps and reduce the amount of Perl wrapper code.

****   Create tests for existing support for operator overloading

Tcl
---

Ruby
----

****   The "Resource Management in Proxies" section of the "SWIG and C++"
       chapter discusses how proxies' ownership of their associated C++
       object can change, and the use of the special disown() and
       acquire() methods to change this ownership status. Need to
       address this for Ruby as well.

***    Add support for keyword arguments (by collecting them in a hash?).

Java
----


C#
--

PHP
---

****   Look at moving to using the UTL.

***    Director support.

**     When returning wrapped objects via alternate constructors if that
       pointer value already exists "out there" as a resource we should
       use the same resource, we can't have multiple ref-counted resources
       mapping to the same object in case it gets twice destroyed.  And check
       if ref count destroying is even working, see smart_pointer_rename

*      Work out how classes without even inherited constructors should
       interact with the php "new <class>" notation.
       See: abstract_inherit_wrap.cpptest

**     Look at pass by point and passby ref,
       Make sometype** to be auto allocated
       Make sometype& and sometype* to be autoallocated IF THEY ARE NOT
       ALREADY swigtype wrapped.

*      Review to see what else is missing!

Guile
-----

**     Maybe rename slot setters from CLASS-SLOT-set to CLASS-SLOT-set!
       to match Scheme convention for naming of mutators.

**     Support keyword args.

**     Director Support!

**     Cleaner handling of multiple values.
       Use a typemap keyword argument "numoutputs" of "out" and
       "argout" to indicate how many values are returned.

**     Make SWIG's types first-class by using a separate smob type for
       SWIG type descriptors; enable reflection on types.  (Maybe
       GOOPS metaclasses?)

**     Provide a clean way to construct type predicates.

**     In GOOPS mode, maybe make overloaded functions methods. 

**     Increase the safety of destructor functions.  John Lenz suggests:

	  I think the best way of doing this would be to use %feature to mark  
	  which classes allow for "normal" <swig> smobs to be deleted explicitly.

	  We separate pointers into two classes, those that can be deleted from  
	  scheme and those that can't.  The pointers that can be deleted use the
	  <collectable-swig> smob and those that can not be deleted use the  
	  <swig> smob.  A user can specify which type of each object they want  
	  with %newobject and the CONSUMED typemap.

	  By default, the exported destructor will only accept <collectable-swig>  
	  smobs, because by definition, collectable-swig smobs are those that can  
	  be deleted from scheme.  This allows for the user to implement  
	  protection.  In the interface file, the user has complete control over  
	  which objects can and can not be deleted, and can guarantee that  
	  objects that should not be deleted can not be deleted, and that objects  
	  that should eventually be deleted will be garbage collected.

	  This protection can then be overridden with a %feature directive,  
	  something like

	  %feature("guile_allow_destroy_all","1") Foo::~Foo;

	  I don't know what word we want to use, guile_allow_destroy_all is kinda  
	  bad.  This feature would then allow for a <swig Foo *> smob to be  
	  deleted by passing it to the destructor.  This would allow users to  
	  maintain the protection on other classes, only manually overriding the  
	  protection on the classes that need it.


Mzscheme
--------

**     Port list-vector.i and pointer-in-out.i from Guile.

**     Add shadow class support for the Swindle system. 

Pike
----

*      Decide how to handle global variables (probably using something
       like the Python module's cvar). Affects Examples/pike/simple.

*      Decide how to handle static class member functions and member
       variables.

*      Should investigate the possibility of generating .cmod files
       in addition to straight C/C++ code for extensions.

Common Lisp
-----------

*      Random thoughts by mkoeppe on supporting Common Lisp implementations:

       There are many different Foreign Function Interfaces (FFI) for
       the various CL implementations.  Probably SWIG should interface
       to UFFI, a least-common-denominator FFI that supports many
       implementations.

       Via the s-expression SWIG module we can export SWIG's parse
       tree and import it into CL.  It remains to check if all
       relevant information is dumped (for instance, the type
       information).  Experimental code is available to generate
       low-level UFFI declarations from this parse tree.

       However, for wrapping C++, we also need to create C wrappers
       because most FFIs cannot directly import C++.  A CL SWIG module
       could be exporting both these wrappers and UFFI declarations.
       I have experimental code (not checked in yet) that does this.

       This is fine for generating low-level wrappers. But how do we
       support user typemaps (like converting lists and vectors to C
       arrays on input)?  We have to generate Lisp code that does the
       conversion and then calls the low-level wrapper.  If we
       generate Lisp code, it should be beautiful and readable.
       Therefore, we need at least a Lisp pretty printer.  A Lisp
       pretty printer works best when the Lisp program is represented
       not as text but as Lisp data.  Moreover, typemap writers will
       feel very much constrained by SWIG's capabilities for
       generating wrapper code, when compared to writing Lisp macros.
       Thus we would need half a re-implementation of Lisp in SWIG to
       make users happy.

       The solution could be the following:

**     Build a SWIG library (again) and load it into a Common Lisp
       implementation.

       The FFI declarations could be written manually, or this could
       be bootstrapped via the s-expression module or the primitive
       UFFI wrappers.  This should be easy because SWIG's API is quite
       simple. 

       The embedded SWIG would be driven by a CL program.  High-level
       typemaps would be written as Lisp programs that generate Lisp
       code.

Ocaml
-----
**     I've been working with my camlp4 module and type information
       from the compiler.  When I'm done, the user will have access
       to type inference when writing code, when the inference is
       unambiguous.  This allows the user to write x = _foo 1.0
       instead of x = get_float (_foo (C_float 1.0)).  It's not as
       easy as it sounds, because O'caml doesn't keep type information
       at run time, and doesn't really have a mechanism for doing what
       I need.  However, it's possible to write a preprocessor that
       inserts correct type info at compile time.

       That having been said, the program must compile for type info
       to be available, so I need to attend to a lot of details;  The
       program must compile both with and without type augmentation.
       
Xml
---


Documentation
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****   Extending SWIG (and internals).

***    Perl, Python, Tcl modules.

***    add section for Perl module support for operator overloading

**     Add section on WAD.