- Don't cast between object and function pointers.
- Use standard compliant `__VA_ARGS__` in macros.
- Add explicit `__extension__` on unnamed union in struct (it's a GNU
extension).
- Remove ; after function definitions.
- Replace `const T foo = 3;` for integral types `T` with `enum { foo = 3 };`.
Folding integral constants like that as compile time constants is a GNU
extension. Arrays allocated with `foo` as dimension are VLAs on strictly
compliant C99 compilers.
- Replace empty initialiser list `{}` with zero-initialiser-list `{0}`.
The former is a GNU extension meaning the latter.
- Cast `T*` (where `T != void`) to `void *` in format arguments. While any
object pointer can be implicitly converted to and from `void *`, this
conversion does not happen in variadic function calls.
- Replace arithmetic on `void *` with arithmetic on `char *`. The former
is non-compliant.
- Replace non-`int`-derived types (like `uint16_t`, which is
`short`-derived) in bit fields with `int`-derived types. Using any type
other than `int` or `unsigned int` (or any of their aliases) in bit
fields is a GNU extension.
