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#![stable(feature = "", since = "1.30.0")]
#![allow(non_camel_case_types)]
//! Utilities related to FFI bindings.
use crate::fmt;
use crate::marker::PhantomData;
use crate::ops::{Deref, DerefMut};
/// 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.
///
/// [pointer]: ../../std/primitive.pointer.html
/// [Nomicon]: https://doc.rust-lang.org/nomicon/ffi.html#representing-opaque-structs
// N.B., 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 and we need at least one variant as otherwise the enum
// would be uninhabited and at least dereferencing such pointers would
// be UB.
#[repr(u8)]
#[stable(feature = "raw_os", since = "1.1.0")]
pub enum c_void {
#[unstable(feature = "c_void_variant", reason = "temporary implementation detail",
issue = "0")]
#[doc(hidden)] __variant1,
#[unstable(feature = "c_void_variant", reason = "temporary implementation detail",
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")
}
}
/// Basic implementation of a `va_list`.
// The name is WIP, using `VaListImpl` for now.
#[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
not(target_arch = "x86_64"), not(target_arch = "asmjs")),
all(target_arch = "aarch64", target_os = "ios"),
windows))]
#[repr(transparent)]
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
#[lang = "va_list"]
pub struct VaListImpl<'f> {
ptr: *mut c_void,
// Invariant over `'f`, so each `VaListImpl<'f>` object is tied to
// the region of the function it's defined in
_marker: PhantomData<&'f mut &'f c_void>,
}
#[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
not(target_arch = "x86_64"), not(target_arch = "asmjs")),
all(target_arch = "aarch64", target_os = "ios"),
windows))]
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<'f> fmt::Debug for VaListImpl<'f> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "va_list* {:p}", self.ptr)
}
}
/// AArch64 ABI implementation of a `va_list`. See the
/// [AArch64 Procedure Call Standard] for more details.
///
/// [AArch64 Procedure Call Standard]:
/// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055b/IHI0055B_aapcs64.pdf
#[cfg(all(target_arch = "aarch64", not(target_os = "ios"), not(windows)))]
#[repr(C)]
#[derive(Debug)]
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
#[lang = "va_list"]
pub struct VaListImpl<'f> {
stack: *mut c_void,
gr_top: *mut c_void,
vr_top: *mut c_void,
gr_offs: i32,
vr_offs: i32,
_marker: PhantomData<&'f mut &'f c_void>,
}
/// PowerPC ABI implementation of a `va_list`.
#[cfg(all(target_arch = "powerpc", not(windows)))]
#[repr(C)]
#[derive(Debug)]
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
#[lang = "va_list"]
pub struct VaListImpl<'f> {
gpr: u8,
fpr: u8,
reserved: u16,
overflow_arg_area: *mut c_void,
reg_save_area: *mut c_void,
_marker: PhantomData<&'f mut &'f c_void>,
}
/// x86_64 ABI implementation of a `va_list`.
#[cfg(all(target_arch = "x86_64", not(windows)))]
#[repr(C)]
#[derive(Debug)]
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
#[lang = "va_list"]
pub struct VaListImpl<'f> {
gp_offset: i32,
fp_offset: i32,
overflow_arg_area: *mut c_void,
reg_save_area: *mut c_void,
_marker: PhantomData<&'f mut &'f c_void>,
}
/// asm.js ABI implementation of a `va_list`.
// asm.js uses the PNaCl ABI, which specifies that a `va_list` is
// an array of 4 32-bit integers, according to the old PNaCl docs at
// https://web.archive.org/web/20130518054430/https://www.chromium.org/nativeclient/pnacl/bitcode-abi#TOC-Derived-Types
// and clang does the same in `CreatePNaClABIBuiltinVaListDecl` from `lib/AST/ASTContext.cpp`
#[cfg(all(target_arch = "asmjs", not(windows)))]
#[repr(C)]
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
#[lang = "va_list"]
pub struct VaListImpl<'f> {
inner: [crate::mem::MaybeUninit<i32>; 4],
_marker: PhantomData<&'f mut &'f c_void>,
}
#[cfg(all(target_arch = "asmjs", not(windows)))]
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<'f> fmt::Debug for VaListImpl<'f> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
unsafe {
write!(f, "va_list* [{:#x}, {:#x}, {:#x}, {:#x}]",
self.inner[0].read(), self.inner[1].read(),
self.inner[2].read(), self.inner[3].read())
}
}
}
/// A wrapper for a `va_list`
#[repr(transparent)]
#[derive(Debug)]
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
pub struct VaList<'a, 'f: 'a> {
#[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
not(target_arch = "x86_64"), not(target_arch = "asmjs")),
all(target_arch = "aarch64", target_os = "ios"),
windows))]
inner: VaListImpl<'f>,
#[cfg(all(any(target_arch = "aarch64", target_arch = "powerpc",
target_arch = "x86_64", target_arch = "asmjs"),
any(not(target_arch = "aarch64"), not(target_os = "ios")),
not(windows)))]
inner: &'a mut VaListImpl<'f>,
_marker: PhantomData<&'a mut VaListImpl<'f>>,
}
#[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
not(target_arch = "x86_64"), not(target_arch = "asmjs")),
all(target_arch = "aarch64", target_os = "ios"),
windows))]
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<'f> VaListImpl<'f> {
/// Convert a `VaListImpl` into a `VaList` that is binary-compatible with C's `va_list`.
#[inline]
pub fn as_va_list<'a>(&'a mut self) -> VaList<'a, 'f> {
VaList {
inner: VaListImpl { ..*self },
_marker: PhantomData,
}
}
}
#[cfg(all(any(target_arch = "aarch64", target_arch = "powerpc",
target_arch = "x86_64", target_arch = "asmjs"),
any(not(target_arch = "aarch64"), not(target_os = "ios")),
not(windows)))]
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<'f> VaListImpl<'f> {
/// Convert a `VaListImpl` into a `VaList` that is binary-compatible with C's `va_list`.
#[inline]
pub fn as_va_list<'a>(&'a mut self) -> VaList<'a, 'f> {
VaList {
inner: self,
_marker: PhantomData,
}
}
}
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<'a, 'f: 'a> Deref for VaList<'a, 'f> {
type Target = VaListImpl<'f>;
#[inline]
fn deref(&self) -> &VaListImpl<'f> {
&self.inner
}
}
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<'a, 'f: 'a> DerefMut for VaList<'a, 'f> {
#[inline]
fn deref_mut(&mut self) -> &mut VaListImpl<'f> {
&mut self.inner
}
}
// The VaArgSafe trait needs to be used in public interfaces, however, the trait
// itself must not be allowed to be used outside this module. Allowing users to
// implement the trait for a new type (thereby allowing the va_arg intrinsic to
// be used on a new type) is likely to cause undefined behavior.
//
// FIXME(dlrobertson): In order to use the VaArgSafe trait in a public interface
// but also ensure it cannot be used elsewhere, the trait needs to be public
// within a private module. Once RFC 2145 has been implemented look into
// improving this.
mod sealed_trait {
/// Trait which whitelists the allowed types to be used with [VaList::arg]
///
/// [VaList::va_arg]: struct.VaList.html#method.arg
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
pub trait VaArgSafe {}
}
macro_rules! impl_va_arg_safe {
($($t:ty),+) => {
$(
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl sealed_trait::VaArgSafe for $t {}
)+
}
}
impl_va_arg_safe!{i8, i16, i32, i64, usize}
impl_va_arg_safe!{u8, u16, u32, u64, isize}
impl_va_arg_safe!{f64}
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<T> sealed_trait::VaArgSafe for *mut T {}
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<T> sealed_trait::VaArgSafe for *const T {}
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<'f> VaListImpl<'f> {
/// Advance to the next arg.
#[inline]
pub unsafe fn arg<T: sealed_trait::VaArgSafe>(&mut self) -> T {
va_arg(self)
}
/// Copies the `va_list` at the current location.
pub unsafe fn with_copy<F, R>(&self, f: F) -> R
where F: for<'copy> FnOnce(VaList<'copy, 'f>) -> R {
let mut ap = self.clone();
let ret = f(ap.as_va_list());
va_end(&mut ap);
ret
}
}
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<'f> Clone for VaListImpl<'f> {
#[inline]
fn clone(&self) -> Self {
let mut dest = crate::mem::MaybeUninit::uninit();
unsafe {
va_copy(dest.as_mut_ptr(), self);
dest.assume_init()
}
}
}
#[unstable(feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930")]
impl<'f> Drop for VaListImpl<'f> {
fn drop(&mut self) {
// FIXME: this should call `va_end`, but there's no clean way to
// guarantee that `drop` always gets inlined into its caller,
// so the `va_end` would get directly called from the same function as
// the corresponding `va_copy`. `man va_end` states that C requires this,
// and LLVM basically follows the C semantics, so we need to make sure
// that `va_end` is always called from the same function as `va_copy`.
// For more details, see https://github.com/rust-lang/rust/pull/59625
// and https://llvm.org/docs/LangRef.html#llvm-va-end-intrinsic.
//
// This works for now, since `va_end` is a no-op on all current LLVM targets.
}
}
extern "rust-intrinsic" {
/// Destroy the arglist `ap` after initialization with `va_start` or
/// `va_copy`.
fn va_end(ap: &mut VaListImpl<'_>);
/// Copies the current location of arglist `src` to the arglist `dst`.
fn va_copy<'f>(dest: *mut VaListImpl<'f>, src: &VaListImpl<'f>);
/// Loads an argument of type `T` from the `va_list` `ap` and increment the
/// argument `ap` points to.
fn va_arg<T: sealed_trait::VaArgSafe>(ap: &mut VaListImpl<'_>) -> T;
}