- stdlib.h
- stddef.h
- stdint.h
- stdarg.h
- limits.h
- float.h

The `MRB_OBJ_ALLOC()` macro function returns a pointer of the type corresponding to the constant literal defined in `enum mrb_vtype`.

* `mrb_cstr_to_inum()`
* `mrb_cstr_to_dbl()`

Instead of using copyrighted `strtod`, now use the public domain
implementation of `strtod` by Yasuhiro Matsumoto (@mattn). The function
has been renamed to `mrb_float_read()`; ref #5460 as well.

Consistent number conversion function names:
* `mrb_value` to immediate (C) value
  * `mrb_int()` -> `mrb_as_int()`
  * `mrb_to_flo()` -> `mrb_as_float()`
* `mrb_value` to `mrb_value` (converted)
  * `mrb_to_int()'
  * `mrb_Integer()` - removed
  * `mrb_Float()` -> `mrb_to_float`

Consistent function name (avoid `_flo` suffix):
* `mrb_div_flo()` -> `mrb_div_float`

When the receiver is the instance of subclass of `String`.

- `String#each_char`
- `String#each_line`
- `String#partition`

The GitHub Super Linter is a more robust and better supported
tool than the current GitHub Actions we are using.

Running these checks:

ERROR_ON_MISSING_EXEC_BIT: true
VALIDATE_BASH: true
VALIDATE_BASH_EXEC: true
VALIDATE_EDITORCONFIG: true
VALIDATE_MARKDOWN: true
VALIDATE_SHELL_SHFMT: true
VALIDATE_YAML: true

https://github.com/marketplace/actions/super-linter
https://github.com/github/super-linter

Added the GitHub Super Linter badge to the README.

Also updated the pre-commit framework and added
more documentation on pre-commit.

Added one more pre-commit check: check-executables-have-shebangs

Added one extra check for merge conflicts to our
GitHub Actions.

EditorConfig and Markdown linting.

Minor grammar and spelling fixes.

Update linter.yml

This reverts commit dc51d89a.

Instead of including `mruby/presym.h` everywhere, we provided the
fallback `mruby/presym.inc` under `include/mruby` directory, and specify
`-I<build-dir>/include` before `-I<top-dir>/include` in `presym.rake`.
So even when someone drops `-I<build-dir>/include` in compiler options,
it just compiles without failure.

Addressed an issue where existing programs linking `libmruby.a` could only
be built by adding `<build-dir>/include` to compiler's include path.

The first byte of UTF-8 character should not be `80..c1`.

Also avoid using `uint64_t`.

I misunderstand the meaning of #4483. Sorry.

- Remove `mrb_ssize`
- Fix `MRB_FIXNUM_{MIN,MAX}` to 32 bits on `MRB_NAN_BOXING`

Redirect `mrb_str_to_str` to `mrb_obj_as_string` via C macro.
Inspired by #5082

Rename new functions:

- `mrb_convert_type(mrb,val,type,tname,method)`
   => `mrb_type_convert(mrb,val,type,tname,method)`
- `mrb_check_convert_type(mrb,val,type,tname,method)`
   => `mrb_type_convert_check(mrb,val,type,tname,method)`

Old names are defined by macros (support `tname` drop and
`char*` => `mrb_sym` conversion).

- Integrate `Fixnum` and `Integer`
- Remove `Integral`
- `int / int -> int`
- Replace `mrb_fixnum()` to `mrb_int()`
- Replace `mrb_fixnum_value()` to `mrb_int_value()`.
- Use `mrb_integer_p()` instead of `mrb_fixnum_p()`

We still have `#define MRB_TT_FIXNUM MRB_TT_INTEGER` for compatibility.

* The `Fixnum` constant is now an alias for the `Integer` class.
* Remove `struct mrb_state::fixnum_class` member.
  If necessary, use `struct mrb_state::integer_class` instead.

- `MRB_WITHOUT_FLOAT` => `MRB_NO_FLOAT`
- `MRB_USE_FLOAT` => `MRB_USE_FLOAT32`

The former is to use `USE_XXX` naming convention. The latter is to make
sure `float` is 32bit float and not floating point number in general.

Changes:
- `pool format is completely replaced
  - supported types: `STR`, `INT32`, `INT64`, `FLOAT`
  - `FLOAT` may be replaced by binary representation in the future
- insert `NUL` after string literals in `mrb` files
- `irep->pool` no longer store values in `mrb_value`
- instead it stores in `mrb_pool_value`
- less allocation
- `mrb_irep` can be stored in ROM

- `mrb_convert_type`
- `mrb_check_convert_type`

Those function no longer take `tname` string representation of desired
type, and take method symbols instead of `const char*` names. This is
incompatible change. I hope no third-party gems use those functions.

since mrb_str_to_str() also does it.

Note that the home brew version of `mrb_static_assert` only works within
the function body.  This reverts commit 8f99689b.

`mrb_get_arg1()` raises `ArgumentError` if the method does not receive one
argument.

And replaces all `mrb_get_args(mrb, "o", &arg)` by the new function.

- mrb_utf8len() - returns the size of a UTF-8 char (in bytes)
- mrb_utf8_strlen() - returns the length of a UTF-8 string (in char)