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Diffstat (limited to 'library/core/src/ffi.rs')
| -rw-r--r-- | library/core/src/ffi.rs | 405 |
1 files changed, 405 insertions, 0 deletions
diff --git a/library/core/src/ffi.rs b/library/core/src/ffi.rs new file mode 100644 index 00000000000..e9689af39d5 --- /dev/null +++ b/library/core/src/ffi.rs @@ -0,0 +1,405 @@ +#![stable(feature = "", since = "1.30.0")] +#![allow(non_camel_case_types)] + +//! Utilities related to foreign function interface (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. +/// +/// 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]. +/// +/// [pointer]: ../../std/primitive.pointer.html +/// [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 +// 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 = "core_c_void", since = "1.30.0")] +pub enum c_void { + #[unstable( + feature = "c_void_variant", + reason = "temporary implementation detail", + issue = "none" + )] + #[doc(hidden)] + __variant1, + #[unstable( + feature = "c_void_variant", + reason = "temporary implementation detail", + issue = "none" + )] + #[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")), + all(target_arch = "aarch64", target_os = "ios"), + target_arch = "wasm32", + target_arch = "asmjs", + 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")), + all(target_arch = "aarch64", target_os = "ios"), + target_arch = "wasm32", + target_arch = "asmjs", + 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>, +} + +/// 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") + ), + all(target_arch = "aarch64", target_os = "ios"), + target_arch = "wasm32", + target_arch = "asmjs", + windows + ))] + inner: VaListImpl<'f>, + + #[cfg(all( + any(target_arch = "aarch64", target_arch = "powerpc", target_arch = "x86_64"), + any(not(target_arch = "aarch64"), not(target_os = "ios")), + not(target_arch = "wasm32"), + not(target_arch = "asmjs"), + 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")), + all(target_arch = "aarch64", target_os = "ios"), + target_arch = "wasm32", + target_arch = "asmjs", + 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"), + any(not(target_arch = "aarch64"), not(target_os = "ios")), + not(target_arch = "wasm32"), + not(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> 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 permits the allowed types to be used with [VaList::arg]. + /// + /// [VaList::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 { + // SAFETY: the caller must uphold the safety contract for `va_arg`. + unsafe { 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()); + // SAFETY: the caller must uphold the safety contract for `va_end`. + unsafe { + 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(); + // SAFETY: we write to the `MaybeUninit`, thus it is initialized and `assume_init` is legal + 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; +} |