Below are the changes for the current release.
See the CHANGES file for changes in older releases.
See the RELEASENOTES file for a summary of changes in each release.
Issue # numbers mentioned below can be found on Github. For more details, add
the issue number to the end of the URL: https://github.com/swig/swig/issues/

Version 4.2.0 (in progress)
===========================

2023-04-19: mmomtchev
            https://sourceforge.net/p/swig/bugs/1163/ #2525 Fix preprocessor
            expansion when a macro expands to the name of another macro which
            takes parameters from the input following the original macro
            expansion.

2023-04-19: wildmaples
	    [Ruby] #2527 Fix "undefining the allocator of T_DATA" warning seen
	    with Ruby 3.2.

2023-04-18: davidcl
	    [Scilab] #894 extract values with ":" for typemap (int* IN, int IN_SIZE)

2023-04-14: olly
	    [PHP7] Support for PHP7 has been removed.  PHP7 security support
	    ended 2022-11-28 so it doesn't make sense to include support for
	    it in the SWIG 4.2.x release series.

	    *** POTENTIAL INCOMPATIBILITY ***

2023-03-25: alatina 
            [Octave] #2512 Add support for Octave 8.1.

2023-03-22: wsfulton
            [C#] #2478 Minor enhancements to std::array wrappers in std_array.i.

2023-03-13: wsfulton
            Improved error checking when using %template to instantiate templates within
            the correct scope.

            1. When a template is instantiated via %template and uses the unary scope
            operator ::, an error occurs if the instantiation is attempted within a
            namespace that does not enclose the instantiated template.
            For example, the following will now error as ::test::max is not enclosed within test1:

            Error: '::test::max' resolves to 'test::max' and was incorrectly instantiated in
            scope 'test1' instead of within scope 'test'.
              namespace test1 {
                %template(maxchar) ::test::max<char>;
              }

            2. SWIG previously failed to always detect a template did not exist when using
            %template. In particular when instantiating a global template incorrectly within
            namespace. The code below now correctly emits an error:

            Error: Template 'test5::GlobalVector' undefined.
              namespace test5 {
              }
              template<typename T> struct GlobalVector {};
              %template(GVI) test5::GlobalVector<int>;

2023-03-13: wsfulton
            Error out if an attempt is made to define a class using the unary scope
            operator ::. The following is not legal C++ and now results in an error:

            Error: Using the unary scope operator :: in class definition '::Space2::B' is invalid.
              namespace Space2 {
                struct B;
              }
              struct ::Space2::B {};

2023-03-08: wsfulton
            Fix duplicate const in generated code when template instantiation type is const
            and use of template parameter is also explicitly const, such as:

              template <typename T> struct Conster {
                void cccc1(T const& t) {}
              };
              %template(ConsterInt) Conster<const int>;

            Above previously led to generated code:
              (arg1)->cccc1((int const const &)*arg2);
            instead of
              (arg1)->cccc1((int const &)*arg2);

2023-03-01: wsfulton
            Partial template specialization fixes to support default arguments from the primary
            template's parameter list.

              template<class Y, class T=int> struct X { void primary() {} };
              // Previously the specialization below resulted in:
              // Error: Inconsistent argument count in template partial specialization. 1 2
              template<class YY> struct X<YY*> { void special(YY*) {} };

              // Both of these correctly wrap the partially specialized template
              %template(StringPtr) X<const char *>;
              %template(ShortPtr) X<short *, int>;

2023-02-15: wsfulton
            #1300 Further partial template specialization fixes.
            Fixes when templates are used as a template parameter in a partially specialized
            instantiation such as:

              template<typename V> struct Vect {};
              template<class T, typename TT> class Foo { ... };
              template<class TS, typename TTS> class Foo<Vect<TS>, TTS> { ... };
              %template(VectInt) Vect<int>;
              %template(FooVectIntDouble) Foo<Vect<int>, double>; // was previously attempting to use primary template

            Also fixes partial specialization where the same template parameter name is used twice,
            for example:

              template<typename X, typename Y> struct H { ... };
              template<typename T> struct H<T, T> { ... };
              %template(HInts) H<int, int>; // was previously attempting to use primary template

2023-01-27: jschueller
	    #2492 [python] Fix unused parameter warnings for self parameter in
	    generated C/C++ wrapper code.

2023-01-14: wsfulton
            Fix deduction of partially specialized template parameters when the specialized
            parameter is non-trivial, used in a wrapped method and the type to %template uses
            typedefs. For example:

              typedef double & DoubleRef;
              template <typename T> struct XX {};
              template <typename T> struct XX<T &> { void fn(T t) {} };
              %template(XXD) XX<DoubleRef>;

            The type of the parameter in the instantiated template for fn is now correctly deduced
            as double.

2023-01-03: wsfulton
            #983 Fix seg fault when instantiating templates with parameters that are function
            parameters containing templates, such as:

              %template(MyC) C<int(std::vector<int>)>;

2023-01-03: wsfulton
            Complete support for C++11 variadic function templates. Support was previously limited
            to just one template parameter. Now zero or more template parameters are supported
            in the %template instantiation.

2022-12-29: wsfulton
            #1863 Syntax error fixes parsing more elaborate parameter pack arguments that are
            used in function pointers, member function pointers:

              template <typename... V> struct VariadicParms {
                void ParmsFuncPtrPtr(int (*)(V*...)) {}
                void ParmsFuncPtrPtrRef(int (*)(V*&...)) {}
                void ParmsFuncPtrPtrRValueRef(int (*)(V*&&...)) {}
                void ParmsFuncPtrRef(int (*)(V&...)) {}
                void ParmsFuncPtrRValueRef(int (*)(V&&...)) {}

                void ParmsMemFuncPtrPtr(int (KlassMemFuncs::*)(V*...)) {}
                void ParmsMemFuncPtrPtrRef(int (KlassMemFuncs::*)(V*&...)) {}
                void ParmsMemFuncPtrPtrRValueRef(int (KlassMemFuncs::*)(V*&&...)) {}
                void ParmsMemFuncPtrRef(int (KlassMemFuncs::*)(V&...)) {}
                void ParmsMemFuncPtrRValueRef(int (KlassMemFuncs::*)(V&&...)) {}
              };

              %template(VariadicParms0) VariadicParms<>;
              %template(VariadicParms1) VariadicParms<A>;

            Also in various other places such as within noexcept specifiers:

              template<typename T, typename... Args>
              void emplace(Args &&... args) noexcept(
                  std::is_nothrow_constructible<T, Args &&...>::value);

2022-12-27: wsfulton
            Fix instantiation of variadic class templates containing parameter pack arguments that
            are function pointers.

              template <typename... V> struct VariadicParms {
                void ParmsFuncPtrVal(int (*)(V...)) {}
              };

              %template(VariadicParms0) VariadicParms<>;
              %template(VariadicParms1) VariadicParms<A>;

2022-12-23: wsfulton
            #1863 Fix syntax error parsing variadic templates containing parameter pack arguments that
            are function pointers.

2022-12-22: wsfulton
            Complete support for C++11 variadic class templates. Support was previously limited
            to just one template parameter. Now zero or more template parameters are supported.

2022-12-06: wsfulton
            #1636 Fix syntax error for misplaced Doxygen comment after struct/class member.
            Fix syntax error using Doxygen member groups syntax, "///*}", when used after
            final struct/class member.

2022-12-05: wsfulton
            #2023 Fix garbled Doxygen post comments in parameter lists.
            Fix syntax error parsing a trailing Doxygen comment in parameter lists.

2022-12-03: wsfulton
            #1609 Fix syntax error parsing of Doxygen comments after last enum item.

2022-12-03: wsfulton
            #1715 Fix syntax error parsing of unconventionally placed Doxygen post
            comments for enum items.

2022-12-02: wsfulton
            #624 #1021 Improved template template parameters support. Previously, specifying more
            than one simple template template parameter resulted in a parse error. Now
            multiple template template parameters are working including instantiation with
            %template. Example:

              template <template<template<class> class, class> class Op, template<class> class X, class Y>
              class C { ... };

2022-11-26: wsfulton
            #1589 #1590 Slightly better decltype() support for expressions, such as:

              int i,j;
              ...  decltype(i+j) ...
              ...  decltype(&i) ...

            These result in a warning for non-trivial expressions which SWIG cannot evaluate:

              Warning 344: Unable to deduce decltype for 'i+j'.

            See 'Type Inference' in CPlusPlus.html for workarounds.

2022-11-22: wsfulton
            #1037 Fix seg fault handling template parameter expressions containing '<='
            or '>='.

2022-11-18: wsfulton
            Duplicate class template instantiations via %template now issue a warning and are ignored.

                %template(Aint) A<int>;
                %template(Aint2) A<int>; // Now ignored and issues a warning

            example.i:7: Warning 404: Duplicate template instantiation of 'A< int >' with name 'Aint2' ignored,
            example.i:6: Warning 404: previous instantiation of 'A< int >' with name 'Aint'.

            A single empty template instantiation before a named instantiation is the one exception
            for allowing duplicate template instantiations as the empty template instantation does not
            create a wrapper for the template, it merely adds the instantiation into SWIG's internal
            type system.
            Duplicate empty template instantiations are quietly ignored.

                %template() B<int>;
                %template(Bint) B<int>; // OK

                %template() C<int>;
                %template() C<int>; // Quietly ignored now
                %template(Cint) C<int>; // OK

            Note that default template parameters are considered when looking for duplicates such as:

                template <typename T, typename U = short> struct D {};
                %template(Dint) D<int>;
                %template(Dintshort) D<int, short>;

            example.i:7: Warning 404: Duplicate template instantiation of 'D< int,short >' with name 'Dintshort' ignored,
            example.i:6: Warning 404: previous instantiation of 'D< int >' with name 'Dint'.

            Note that the following always was ignored, but that was because the chosen name was a
            duplicate rather than the template being a duplicate:

                %template(Eint) E<int>;
                %template(Eint) E<int>; // Always has been ignored as a redefined identifier

            The old warning was:

            example.i:7: Warning 302: Identifier 'Eint' redefined (ignored) (Renamed from 'E< int >'),
            example.i:6: Warning 302: previous definition of 'Eint' (Renamed from 'E< int >').

	    *** POTENTIAL INCOMPATIBILITY ***