library/core/src/ffi/c_void.md - rust - Git at Google

 Equivalent to C's `void` type when used as a [pointer].

 In essence, `*const c_void` is equivalent to C's `const void*`
 and `*mut c_void` is equivalent to C's `void*`. That said, this is
 *not* the same as C's `void` return type, which is Rust's `()` type.

 To model pointers to opaque types in FFI, until `extern type` is
 stabilized, it is recommended to use a newtype wrapper around an empty
 byte array. See the [Nomicon] for details.

 One could use `std::os::raw::c_void` if they want to support old Rust
 compiler down to 1.1.0. After Rust 1.30.0, it was re-exported by
 this definition. For more information, please read [RFC 2521].

 [Nomicon]: https://doc.rust-lang.org/nomicon/ffi.html#representing-opaque-structs
 [RFC 2521]: https://github.com/rust-lang/rfcs/blob/master/text/2521-c_void-reunification.md
	Equivalent to C's `void` type when used as a [pointer].

	In essence, `const c_void` is equivalent to C's `const void`
	and `mut c_void` is equivalent to C's `void`. That said, this is
	not the same as C's `void` return type, which is Rust's `()` type.

	To model pointers to opaque types in FFI, until `extern type` is
	stabilized, it is recommended to use a newtype wrapper around an empty
	byte array. See the [Nomicon] for details.

	One could use `std::os::raw::c_void` if they want to support old Rust
	compiler down to 1.1.0. After Rust 1.30.0, it was re-exported by
	this definition. For more information, please read [RFC 2521].

	[Nomicon]: https://doc.rust-lang.org/nomicon/ffi.html#representing-opaque-structs
	[RFC 2521]: https://github.com/rust-lang/rfcs/blob/master/text/2521-c_void-reunification.md