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)
===========================

2022-10-26: wsfulton
            [R] #2386 Fix memory leak in R shared_ptr wrappers.
            Fix leak when a cast up a class inheritance chain is required.

2022-10-26: wsfulton
            [R] Improve R wrapper error message when calling overloaded methods
            when incorrect types passed are passed to the overloaded methods.

            Old unhelpful error message:
              Error in f(...) : could not find function "f"

            Example of new improved error message:
              Error in use_count(k) :
                cannot find overloaded function for use_count with argtypes (NULL)

2022-10-27: wsfulton
            [R] Allow NULL to be used in overloaded functions taking shared_ptr.
            Also fixes special variable $argtype expansion in rtypecheck typemaps.

2022-10-28: wsfulton
            [R] R rtypecheck typemaps

            Further switch to use rtypecheck typemaps instead of hard coded logic.
            The full switch to typemaps is deferred until swig-4.2 as it can't be fully
            backwards compatible. For now a warning is provided to help the
            transition. It provides the full typemap that should be placed into
            a user's interface file, for example:

            %typemap("rtype") int32_t * "integer"
            void testmethod(int32_t * i);
            void testmethod();

            If there is no rtypecheck typemap for int32_t *, the warning shown is:

              example.i:7: Warning 750: Optional rtypecheck code is deprecated. Add the
              following typemap to fix as the next version of SWIG will not work without it:
              %typemap("rtypecheck") int32_t * %{ (is.integer($arg) || is.numeric($arg)) %}

            The warning is shown for any code that previously used "numeric", "integer" or
            "character" for the rtype typemap. Copying the rtypecheck typemap as
            shown into the user interface file will provide the appropriate fix and
            the warning will disappear. This is important to do as swig-4.2 will
            not be able to provide this helpful warning.