```
mruby % doxygen -u
warning: Tag 'CLANG_ASSISTED_PARSING' at line 50 of file 'Doxyfile' belongs to an option that was not enabled at compile time.
This tag has been removed.
warning: Tag 'CLANG_OPTIONS' at line 51 of file 'Doxyfile' belongs to an option that was not enabled at compile time.
This tag has been removed.
warning: Tag 'TCL_SUBST' at line 238 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'COLS_IN_ALPHA_INDEX' at line 1075 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'FORMULA_TRANSPARENT' at line 1481 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'LATEX_SOURCE_CODE' at line 1769 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'RTF_SOURCE_CODE' at line 1851 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'DOCBOOK_PROGRAMLISTING' at line 1949 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'PERL_PATH' at line 2094 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'CLASS_DIAGRAMS' at line 2107 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'MSCGEN_PATH' at line 2116 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'DOT_FONTNAME' at line 2158 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'DOT_FONTSIZE' at line 2165 of file 'Doxyfile' has become obsolete.
This tag has been removed.
warning: Tag 'DOT_TRANSPARENT' at line 2391 of file 'Doxyfile' has become obsolete.
This tag has been removed.
Configuration file 'Doxyfile' updated.
```
Since `bin/mruby-config` now points to a directory relative to itself, it is no longer possible to reach `include/` or `lib/`.
Therefore, avoid placing entities in them.
This is so that the build directory can be regarded as a temporary installation directory to work in.
Directories set in `MRuby::Gem::Specification#export_include_paths` are used as they are if they are subdirectories placed under `gem.dir`.
Files are placed under `<build-dir>/include/mruby/gems/<gem-name>/<gem-include_paths>` to separate each GEM.
When GEM is compiled by building `libmruby.a`, the same `include_paths` will be set as before, so it is expected that no unintended references will be made.
This function is the entity of the `Kernel.#raise` or `Kernel#fail` method.
I don't think users can use it whenever they want, and I don't think there is any need to expose it as an entity of a user-defined method.