src/libcore/ffi.rs

#![stable(feature = "", since = "1.30.0")]

#![allow(non_camel_case_types)]

//! Utilities related to FFI bindings.

use ::fmt;

/// 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.
///
/// Ideally, this type would be equivalent to [`!`], but currently it may
/// be more ideal to use `c_void` for FFI purposes.
///
/// [`!`]: ../../std/primitive.never.html
/// [pointer]: ../../std/primitive.pointer.html
// NB: For LLVM to recognize the void pointer type and by extension
//     functions like malloc(), we need to have it represented as i8* in
//     LLVM bitcode. The enum used here ensures this and prevents misuse
//     of the "raw" type by only having private variants.. We need two
//     variants, because the compiler complains about the repr attribute
//     otherwise.
#[repr(u8)]
#[stable(feature = "raw_os", since = "1.1.0")]
pub enum c_void {
    #[unstable(feature = "c_void_variant", reason = "should not have to exist",
               issue = "0")]
    #[doc(hidden)] __variant1,
    #[unstable(feature = "c_void_variant", reason = "should not have to exist",
               issue = "0")]
    #[doc(hidden)] __variant2,
}

#[stable(feature = "std_debug", since = "1.16.0")]
impl fmt::Debug for c_void {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.pad("c_void")
    }
}