From ec921db289ea87fd4030cb7f8a70f6ba3a31c2c7 Mon Sep 17 00:00:00 2001 From: Pavel Grigorenko Date: Sun, 23 Jun 2024 22:11:35 +0300 Subject: [PATCH 1/7] impl CloneToUninit for str and CStr --- library/core/src/clone.rs | 21 +++++++++++++++++++ library/core/tests/clone.rs | 40 +++++++++++++++++++++++++++++++++++++ 2 files changed, 61 insertions(+) diff --git a/library/core/src/clone.rs b/library/core/src/clone.rs index 76a89eaaff86e..409fd2746f588 100644 --- a/library/core/src/clone.rs +++ b/library/core/src/clone.rs @@ -346,6 +346,27 @@ unsafe impl CloneToUninit for [T] { } } +#[unstable(feature = "clone_to_uninit", issue = "126799")] +unsafe impl CloneToUninit for str { + #[cfg_attr(debug_assertions, track_caller)] + unsafe fn clone_to_uninit(&self, dst: *mut Self) { + // SAFETY: str is just a [u8] with UTF-8 invariant + unsafe { self.as_bytes().clone_to_uninit(dst as *mut [u8]) } + } +} + +#[unstable(feature = "clone_to_uninit", issue = "126799")] +unsafe impl CloneToUninit for crate::ffi::CStr { + #[cfg_attr(debug_assertions, track_caller)] + unsafe fn clone_to_uninit(&self, dst: *mut Self) { + // SAFETY: For now, CStr is just a #[repr(trasnsparent)] [c_char] with some invariants. + // And we can cast [c_char] to [u8] on all supported platforms (see: to_bytes_with_nul). + // The pointer metadata properly preserves the length (NUL included). + // See: `cstr_metadata_is_length_with_nul` in tests. + unsafe { self.to_bytes_with_nul().clone_to_uninit(dst as *mut [u8]) } + } +} + /// Ownership of a collection of values stored in a non-owned `[MaybeUninit]`, some of which /// are not yet initialized. This is sort of like a `Vec` that doesn't own its allocation. /// Its responsibility is to provide cleanup on unwind by dropping the values that *are* diff --git a/library/core/tests/clone.rs b/library/core/tests/clone.rs index b7130f16f8795..71a328733b7c4 100644 --- a/library/core/tests/clone.rs +++ b/library/core/tests/clone.rs @@ -1,5 +1,7 @@ use core::clone::CloneToUninit; +use core::ffi::CStr; use core::mem::MaybeUninit; +use core::ptr; #[test] #[allow(suspicious_double_ref_op)] @@ -81,3 +83,41 @@ fn test_clone_to_uninit_slice_drops_on_panic() { drop(a); assert_eq!(COUNTER.load(Relaxed), 0); } + +#[test] +fn test_clone_to_uninit_str() { + let a = "hello"; + + let mut storage: MaybeUninit<[u8; 5]> = MaybeUninit::uninit(); + unsafe { a.clone_to_uninit(storage.as_mut_ptr() as *mut [u8] as *mut str) }; + assert_eq!(a.as_bytes(), unsafe { storage.assume_init() }.as_slice()); + + let mut b: Box = "world".into(); + assert_eq!(a.len(), b.len()); + assert_ne!(a, &*b); + unsafe { a.clone_to_uninit(ptr::from_mut::(&mut b)) }; + assert_eq!(a, &*b); +} + +#[test] +fn test_clone_to_uninit_cstr() { + let a = c"hello"; + + let mut storage: MaybeUninit<[u8; 6]> = MaybeUninit::uninit(); + unsafe { a.clone_to_uninit(storage.as_mut_ptr() as *mut [u8] as *mut CStr) }; + assert_eq!(a.to_bytes_with_nul(), unsafe { storage.assume_init() }.as_slice()); + + let mut b: Box = c"world".into(); + assert_eq!(a.count_bytes(), b.count_bytes()); + assert_ne!(a, &*b); + unsafe { a.clone_to_uninit(ptr::from_mut::(&mut b)) }; + assert_eq!(a, &*b); +} + +#[test] +fn cstr_metadata_is_length_with_nul() { + let s: &CStr = c"abcdef"; + let p: *const CStr = ptr::from_ref(s); + let bytes: *const [u8] = p as *const [u8]; + assert_eq!(s.to_bytes_with_nul().len(), bytes.len()); +} From afabc583f7f646d45f506263a1c331383ebdc252 Mon Sep 17 00:00:00 2001 From: Pavel Grigorenko Date: Sun, 23 Jun 2024 23:05:10 +0300 Subject: [PATCH 2/7] impl CloneToUninit for Path and OsStr --- library/std/src/ffi/os_str.rs | 12 ++++++++++++ library/std/src/ffi/os_str/tests.rs | 17 +++++++++++++++++ library/std/src/lib.rs | 1 + library/std/src/path.rs | 11 +++++++++++ library/std/src/path/tests.rs | 19 +++++++++++++++++++ library/std/src/sys/os_str/bytes.rs | 12 ++++++++++++ library/std/src/sys/os_str/wtf8.rs | 12 ++++++++++++ library/std/src/sys_common/wtf8.rs | 11 +++++++++++ 8 files changed, 95 insertions(+) diff --git a/library/std/src/ffi/os_str.rs b/library/std/src/ffi/os_str.rs index a501bcc98cf38..f68ea3c562a5e 100644 --- a/library/std/src/ffi/os_str.rs +++ b/library/std/src/ffi/os_str.rs @@ -3,10 +3,13 @@ #[cfg(test)] mod tests; +use core::clone::CloneToUninit; + use crate::borrow::{Borrow, Cow}; use crate::collections::TryReserveError; use crate::hash::{Hash, Hasher}; use crate::ops::{self, Range}; +use crate::ptr::addr_of_mut; use crate::rc::Rc; use crate::str::FromStr; use crate::sync::Arc; @@ -1261,6 +1264,15 @@ impl Clone for Box { } } +#[unstable(feature = "clone_to_uninit", issue = "126799")] +unsafe impl CloneToUninit for OsStr { + #[cfg_attr(debug_assertions, track_caller)] + unsafe fn clone_to_uninit(&self, dst: *mut Self) { + // SAFETY: we're just a wrapper around a platform-specific Slice + unsafe { self.inner.clone_to_uninit(addr_of_mut!((*dst).inner)) } + } +} + #[stable(feature = "shared_from_slice2", since = "1.24.0")] impl From for Arc { /// Converts an [`OsString`] into an [Arc]<[OsStr]> by moving the [`OsString`] diff --git a/library/std/src/ffi/os_str/tests.rs b/library/std/src/ffi/os_str/tests.rs index 5b39b9e34d8c7..67147934b4db3 100644 --- a/library/std/src/ffi/os_str/tests.rs +++ b/library/std/src/ffi/os_str/tests.rs @@ -1,4 +1,6 @@ use super::*; +use crate::mem::MaybeUninit; +use crate::ptr; #[test] fn test_os_string_with_capacity() { @@ -286,3 +288,18 @@ fn slice_surrogate_edge() { assert_eq!(post_crab.slice_encoded_bytes(..4), "🦀"); assert_eq!(post_crab.slice_encoded_bytes(4..), surrogate); } + +#[test] +fn clone_to_uninit() { + let a = OsStr::new("hello.txt"); + + let mut storage = vec![MaybeUninit::::uninit(); size_of_val::(a)]; + unsafe { a.clone_to_uninit(ptr::from_mut::<[_]>(storage.as_mut_slice()) as *mut OsStr) }; + assert_eq!(a.as_encoded_bytes(), unsafe { MaybeUninit::slice_assume_init_ref(&storage) }); + + let mut b: Box = OsStr::new("world.exe").into(); + assert_eq!(size_of_val::(a), size_of_val::(&b)); + assert_ne!(a, &*b); + unsafe { a.clone_to_uninit(ptr::from_mut::(&mut b)) }; + assert_eq!(a, &*b); +} diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs index ee6f5a6f3c0d5..5cc6376a32d72 100644 --- a/library/std/src/lib.rs +++ b/library/std/src/lib.rs @@ -323,6 +323,7 @@ // tidy-alphabetical-start #![feature(c_str_module)] #![feature(char_internals)] +#![feature(clone_to_uninit)] #![feature(core_intrinsics)] #![feature(core_io_borrowed_buf)] #![feature(duration_constants)] diff --git a/library/std/src/path.rs b/library/std/src/path.rs index 80163667636ae..d6c78883f2804 100644 --- a/library/std/src/path.rs +++ b/library/std/src/path.rs @@ -70,6 +70,8 @@ #[cfg(test)] mod tests; +use core::clone::CloneToUninit; + use crate::borrow::{Borrow, Cow}; use crate::collections::TryReserveError; use crate::error::Error; @@ -3109,6 +3111,15 @@ impl Path { } } +#[unstable(feature = "clone_to_uninit", issue = "126799")] +unsafe impl CloneToUninit for Path { + #[cfg_attr(debug_assertions, track_caller)] + unsafe fn clone_to_uninit(&self, dst: *mut Self) { + // SAFETY: Path is just a wrapper around OsStr + unsafe { self.inner.clone_to_uninit(core::ptr::addr_of_mut!((*dst).inner)) } + } +} + #[stable(feature = "rust1", since = "1.0.0")] impl AsRef for Path { #[inline] diff --git a/library/std/src/path/tests.rs b/library/std/src/path/tests.rs index a12e42cba0c5c..6436872087d6c 100644 --- a/library/std/src/path/tests.rs +++ b/library/std/src/path/tests.rs @@ -3,6 +3,8 @@ use core::hint::black_box; use super::*; use crate::collections::{BTreeSet, HashSet}; use crate::hash::DefaultHasher; +use crate::mem::MaybeUninit; +use crate::ptr; #[allow(unknown_lints, unused_macro_rules)] macro_rules! t ( @@ -2054,3 +2056,20 @@ fn bench_hash_path_long(b: &mut test::Bencher) { black_box(hasher.finish()); } + +#[test] +fn clone_to_uninit() { + let a = Path::new("hello.txt"); + + let mut storage = vec![MaybeUninit::::uninit(); size_of_val::(a)]; + unsafe { a.clone_to_uninit(ptr::from_mut::<[_]>(storage.as_mut_slice()) as *mut Path) }; + assert_eq!(a.as_os_str().as_encoded_bytes(), unsafe { + MaybeUninit::slice_assume_init_ref(&storage) + }); + + let mut b: Box = Path::new("world.exe").into(); + assert_eq!(size_of_val::(a), size_of_val::(&b)); + assert_ne!(a, &*b); + unsafe { a.clone_to_uninit(ptr::from_mut::(&mut b)) }; + assert_eq!(a, &*b); +} diff --git a/library/std/src/sys/os_str/bytes.rs b/library/std/src/sys/os_str/bytes.rs index 0f8bd6453528e..8529207366e93 100644 --- a/library/std/src/sys/os_str/bytes.rs +++ b/library/std/src/sys/os_str/bytes.rs @@ -1,6 +1,9 @@ //! The underlying OsString/OsStr implementation on Unix and many other //! systems: just a `Vec`/`[u8]`. +use core::clone::CloneToUninit; +use core::ptr::addr_of_mut; + use crate::borrow::Cow; use crate::collections::TryReserveError; use crate::fmt::Write; @@ -345,3 +348,12 @@ impl Slice { self.inner.eq_ignore_ascii_case(&other.inner) } } + +#[unstable(feature = "clone_to_uninit", issue = "126799")] +unsafe impl CloneToUninit for Slice { + #[cfg_attr(debug_assertions, track_caller)] + unsafe fn clone_to_uninit(&self, dst: *mut Self) { + // SAFETY: we're just a wrapper around [u8] + unsafe { self.inner.clone_to_uninit(addr_of_mut!((*dst).inner)) } + } +} diff --git a/library/std/src/sys/os_str/wtf8.rs b/library/std/src/sys/os_str/wtf8.rs index ed975ba58b5e2..e5755a4b87443 100644 --- a/library/std/src/sys/os_str/wtf8.rs +++ b/library/std/src/sys/os_str/wtf8.rs @@ -1,5 +1,8 @@ //! The underlying OsString/OsStr implementation on Windows is a //! wrapper around the "WTF-8" encoding; see the `wtf8` module for more. +use core::clone::CloneToUninit; +use core::ptr::addr_of_mut; + use crate::borrow::Cow; use crate::collections::TryReserveError; use crate::rc::Rc; @@ -268,3 +271,12 @@ impl Slice { self.inner.eq_ignore_ascii_case(&other.inner) } } + +#[unstable(feature = "clone_to_uninit", issue = "126799")] +unsafe impl CloneToUninit for Slice { + #[cfg_attr(debug_assertions, track_caller)] + unsafe fn clone_to_uninit(&self, dst: *mut Self) { + // SAFETY: we're just a wrapper around Wtf8 + unsafe { self.inner.clone_to_uninit(addr_of_mut!((*dst).inner)) } + } +} diff --git a/library/std/src/sys_common/wtf8.rs b/library/std/src/sys_common/wtf8.rs index 277c9506febbb..2bdeff78ddfd6 100644 --- a/library/std/src/sys_common/wtf8.rs +++ b/library/std/src/sys_common/wtf8.rs @@ -19,12 +19,14 @@ mod tests; use core::char::{encode_utf16_raw, encode_utf8_raw}; +use core::clone::CloneToUninit; use core::str::next_code_point; use crate::borrow::Cow; use crate::collections::TryReserveError; use crate::hash::{Hash, Hasher}; use crate::iter::FusedIterator; +use crate::ptr::addr_of_mut; use crate::rc::Rc; use crate::sync::Arc; use crate::sys_common::AsInner; @@ -1046,3 +1048,12 @@ impl Hash for Wtf8 { 0xfeu8.hash(state) } } + +#[unstable(feature = "clone_to_uninit", issue = "126799")] +unsafe impl CloneToUninit for Wtf8 { + #[cfg_attr(debug_assertions, track_caller)] + unsafe fn clone_to_uninit(&self, dst: *mut Self) { + // SAFETY: we're just a wrapper around [u8] + unsafe { self.bytes.clone_to_uninit(addr_of_mut!((*dst).bytes)) } + } +} From dbc13fb309f3a1539e8bb1cdeeb5fbb2e3eaaa43 Mon Sep 17 00:00:00 2001 From: Pavel Grigorenko Date: Mon, 24 Jun 2024 18:09:27 +0300 Subject: [PATCH 3/7] Sparkle some attributes over `CloneToUninit` stuff --- library/core/src/clone.rs | 7 +++++++ library/std/src/ffi/os_str.rs | 1 + library/std/src/path.rs | 1 + library/std/src/sys/os_str/bytes.rs | 1 + library/std/src/sys/os_str/wtf8.rs | 1 + library/std/src/sys_common/wtf8.rs | 1 + 6 files changed, 12 insertions(+) diff --git a/library/core/src/clone.rs b/library/core/src/clone.rs index 409fd2746f588..88f7990c017df 100644 --- a/library/core/src/clone.rs +++ b/library/core/src/clone.rs @@ -272,6 +272,7 @@ pub unsafe trait CloneToUninit { #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for T { + #[inline] default unsafe fn clone_to_uninit(&self, dst: *mut Self) { // SAFETY: The safety conditions of clone_to_uninit() are a superset of those of // ptr::write(). @@ -285,8 +286,10 @@ unsafe impl CloneToUninit for T { // Specialized implementation for types that are [`Copy`], not just [`Clone`], // and can therefore be copied bitwise. +#[doc(hidden)] #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for T { + #[inline] unsafe fn clone_to_uninit(&self, dst: *mut Self) { // SAFETY: The safety conditions of clone_to_uninit() are a superset of those of // ptr::copy_nonoverlapping(). @@ -298,6 +301,7 @@ unsafe impl CloneToUninit for T { #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for [T] { + #[inline] #[cfg_attr(debug_assertions, track_caller)] default unsafe fn clone_to_uninit(&self, dst: *mut Self) { let len = self.len(); @@ -326,8 +330,10 @@ unsafe impl CloneToUninit for [T] { } } +#[doc(hidden)] #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for [T] { + #[inline] #[cfg_attr(debug_assertions, track_caller)] unsafe fn clone_to_uninit(&self, dst: *mut Self) { let len = self.len(); @@ -348,6 +354,7 @@ unsafe impl CloneToUninit for [T] { #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for str { + #[inline] #[cfg_attr(debug_assertions, track_caller)] unsafe fn clone_to_uninit(&self, dst: *mut Self) { // SAFETY: str is just a [u8] with UTF-8 invariant diff --git a/library/std/src/ffi/os_str.rs b/library/std/src/ffi/os_str.rs index f68ea3c562a5e..918eec2d0d8ef 100644 --- a/library/std/src/ffi/os_str.rs +++ b/library/std/src/ffi/os_str.rs @@ -1266,6 +1266,7 @@ impl Clone for Box { #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for OsStr { + #[inline] #[cfg_attr(debug_assertions, track_caller)] unsafe fn clone_to_uninit(&self, dst: *mut Self) { // SAFETY: we're just a wrapper around a platform-specific Slice diff --git a/library/std/src/path.rs b/library/std/src/path.rs index d6c78883f2804..9eaa0e01c2c00 100644 --- a/library/std/src/path.rs +++ b/library/std/src/path.rs @@ -3113,6 +3113,7 @@ impl Path { #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for Path { + #[inline] #[cfg_attr(debug_assertions, track_caller)] unsafe fn clone_to_uninit(&self, dst: *mut Self) { // SAFETY: Path is just a wrapper around OsStr diff --git a/library/std/src/sys/os_str/bytes.rs b/library/std/src/sys/os_str/bytes.rs index 8529207366e93..992767211d083 100644 --- a/library/std/src/sys/os_str/bytes.rs +++ b/library/std/src/sys/os_str/bytes.rs @@ -351,6 +351,7 @@ impl Slice { #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for Slice { + #[inline] #[cfg_attr(debug_assertions, track_caller)] unsafe fn clone_to_uninit(&self, dst: *mut Self) { // SAFETY: we're just a wrapper around [u8] diff --git a/library/std/src/sys/os_str/wtf8.rs b/library/std/src/sys/os_str/wtf8.rs index e5755a4b87443..433237aa6e7bf 100644 --- a/library/std/src/sys/os_str/wtf8.rs +++ b/library/std/src/sys/os_str/wtf8.rs @@ -274,6 +274,7 @@ impl Slice { #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for Slice { + #[inline] #[cfg_attr(debug_assertions, track_caller)] unsafe fn clone_to_uninit(&self, dst: *mut Self) { // SAFETY: we're just a wrapper around Wtf8 diff --git a/library/std/src/sys_common/wtf8.rs b/library/std/src/sys_common/wtf8.rs index 2bdeff78ddfd6..063451ad54e1c 100644 --- a/library/std/src/sys_common/wtf8.rs +++ b/library/std/src/sys_common/wtf8.rs @@ -1051,6 +1051,7 @@ impl Hash for Wtf8 { #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for Wtf8 { + #[inline] #[cfg_attr(debug_assertions, track_caller)] unsafe fn clone_to_uninit(&self, dst: *mut Self) { // SAFETY: we're just a wrapper around [u8] From 110c273f4fb40c318be59a557ba90314fbbc42a6 Mon Sep 17 00:00:00 2001 From: Pavel Grigorenko Date: Wed, 26 Jun 2024 02:22:07 +0300 Subject: [PATCH 4/7] CloneToUninit: use a private specialization trait and move implementation details into a submodule --- library/core/src/clone.rs | 123 ++--------------------------- library/core/src/clone/uninit.rs | 128 +++++++++++++++++++++++++++++++ 2 files changed, 134 insertions(+), 117 deletions(-) create mode 100644 library/core/src/clone/uninit.rs diff --git a/library/core/src/clone.rs b/library/core/src/clone.rs index 88f7990c017df..2150463067205 100644 --- a/library/core/src/clone.rs +++ b/library/core/src/clone.rs @@ -36,8 +36,7 @@ #![stable(feature = "rust1", since = "1.0.0")] -use crate::mem::{self, MaybeUninit}; -use crate::ptr; +mod uninit; /// A common trait for the ability to explicitly duplicate an object. /// @@ -248,7 +247,7 @@ pub unsafe trait CloneToUninit { /// * `dst` must be properly aligned. /// * `dst` must have the same [pointer metadata] (slice length or `dyn` vtable) as `self`. /// - /// [valid]: ptr#safety + /// [valid]: crate::ptr#safety /// [pointer metadata]: crate::ptr::metadata() /// /// # Panics @@ -272,83 +271,20 @@ pub unsafe trait CloneToUninit { #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for T { - #[inline] - default unsafe fn clone_to_uninit(&self, dst: *mut Self) { - // SAFETY: The safety conditions of clone_to_uninit() are a superset of those of - // ptr::write(). - unsafe { - // We hope the optimizer will figure out to create the cloned value in-place, - // skipping ever storing it on the stack and the copy to the destination. - ptr::write(dst, self.clone()); - } - } -} - -// Specialized implementation for types that are [`Copy`], not just [`Clone`], -// and can therefore be copied bitwise. -#[doc(hidden)] -#[unstable(feature = "clone_to_uninit", issue = "126799")] -unsafe impl CloneToUninit for T { #[inline] unsafe fn clone_to_uninit(&self, dst: *mut Self) { - // SAFETY: The safety conditions of clone_to_uninit() are a superset of those of - // ptr::copy_nonoverlapping(). - unsafe { - ptr::copy_nonoverlapping(self, dst, 1); - } + // SAFETY: we're calling a specialization with the same contract + unsafe { ::clone_one(self, dst) } } } #[unstable(feature = "clone_to_uninit", issue = "126799")] unsafe impl CloneToUninit for [T] { - #[inline] - #[cfg_attr(debug_assertions, track_caller)] - default unsafe fn clone_to_uninit(&self, dst: *mut Self) { - let len = self.len(); - // This is the most likely mistake to make, so check it as a debug assertion. - debug_assert_eq!( - len, - dst.len(), - "clone_to_uninit() source and destination must have equal lengths", - ); - - // SAFETY: The produced `&mut` is valid because: - // * The caller is obligated to provide a pointer which is valid for writes. - // * All bytes pointed to are in MaybeUninit, so we don't care about the memory's - // initialization status. - let uninit_ref = unsafe { &mut *(dst as *mut [MaybeUninit]) }; - - // Copy the elements - let mut initializing = InitializingSlice::from_fully_uninit(uninit_ref); - for element_ref in self.iter() { - // If the clone() panics, `initializing` will take care of the cleanup. - initializing.push(element_ref.clone()); - } - // If we reach here, then the entire slice is initialized, and we've satisfied our - // responsibilities to the caller. Disarm the cleanup guard by forgetting it. - mem::forget(initializing); - } -} - -#[doc(hidden)] -#[unstable(feature = "clone_to_uninit", issue = "126799")] -unsafe impl CloneToUninit for [T] { #[inline] #[cfg_attr(debug_assertions, track_caller)] unsafe fn clone_to_uninit(&self, dst: *mut Self) { - let len = self.len(); - // This is the most likely mistake to make, so check it as a debug assertion. - debug_assert_eq!( - len, - dst.len(), - "clone_to_uninit() source and destination must have equal lengths", - ); - - // SAFETY: The safety conditions of clone_to_uninit() are a superset of those of - // ptr::copy_nonoverlapping(). - unsafe { - ptr::copy_nonoverlapping(self.as_ptr(), dst.as_mut_ptr(), len); - } + // SAFETY: we're calling a specialization with the same contract + unsafe { ::clone_slice(self, dst) } } } @@ -374,53 +310,6 @@ unsafe impl CloneToUninit for crate::ffi::CStr { } } -/// Ownership of a collection of values stored in a non-owned `[MaybeUninit]`, some of which -/// are not yet initialized. This is sort of like a `Vec` that doesn't own its allocation. -/// Its responsibility is to provide cleanup on unwind by dropping the values that *are* -/// initialized, unless disarmed by forgetting. -/// -/// This is a helper for `impl CloneToUninit for [T]`. -struct InitializingSlice<'a, T> { - data: &'a mut [MaybeUninit], - /// Number of elements of `*self.data` that are initialized. - initialized_len: usize, -} - -impl<'a, T> InitializingSlice<'a, T> { - #[inline] - fn from_fully_uninit(data: &'a mut [MaybeUninit]) -> Self { - Self { data, initialized_len: 0 } - } - - /// Push a value onto the end of the initialized part of the slice. - /// - /// # Panics - /// - /// Panics if the slice is already fully initialized. - #[inline] - fn push(&mut self, value: T) { - MaybeUninit::write(&mut self.data[self.initialized_len], value); - self.initialized_len += 1; - } -} - -impl<'a, T> Drop for InitializingSlice<'a, T> { - #[cold] // will only be invoked on unwind - fn drop(&mut self) { - let initialized_slice = ptr::slice_from_raw_parts_mut( - MaybeUninit::slice_as_mut_ptr(self.data), - self.initialized_len, - ); - // SAFETY: - // * the pointer is valid because it was made from a mutable reference - // * `initialized_len` counts the initialized elements as an invariant of this type, - // so each of the pointed-to elements is initialized and may be dropped. - unsafe { - ptr::drop_in_place::<[T]>(initialized_slice); - } - } -} - /// Implementations of `Clone` for primitive types. /// /// Implementations that cannot be described in Rust diff --git a/library/core/src/clone/uninit.rs b/library/core/src/clone/uninit.rs new file mode 100644 index 0000000000000..8b738bec796de --- /dev/null +++ b/library/core/src/clone/uninit.rs @@ -0,0 +1,128 @@ +use crate::mem::{self, MaybeUninit}; +use crate::ptr; + +/// Private specialization trait used by CloneToUninit, as per +/// [the dev guide](https://std-dev-guide.rust-lang.org/policy/specialization.html). +pub(super) unsafe trait CopySpec: Clone { + unsafe fn clone_one(src: &Self, dst: *mut Self); + unsafe fn clone_slice(src: &[Self], dst: *mut [Self]); +} + +unsafe impl CopySpec for T { + #[inline] + default unsafe fn clone_one(src: &Self, dst: *mut Self) { + // SAFETY: The safety conditions of clone_to_uninit() are a superset of those of + // ptr::write(). + unsafe { + // We hope the optimizer will figure out to create the cloned value in-place, + // skipping ever storing it on the stack and the copy to the destination. + ptr::write(dst, src.clone()); + } + } + + #[inline] + #[cfg_attr(debug_assertions, track_caller)] + default unsafe fn clone_slice(src: &[Self], dst: *mut [Self]) { + let len = src.len(); + // This is the most likely mistake to make, so check it as a debug assertion. + debug_assert_eq!( + len, + dst.len(), + "clone_to_uninit() source and destination must have equal lengths", + ); + + // SAFETY: The produced `&mut` is valid because: + // * The caller is obligated to provide a pointer which is valid for writes. + // * All bytes pointed to are in MaybeUninit, so we don't care about the memory's + // initialization status. + let uninit_ref = unsafe { &mut *(dst as *mut [MaybeUninit]) }; + + // Copy the elements + let mut initializing = InitializingSlice::from_fully_uninit(uninit_ref); + for element_ref in src { + // If the clone() panics, `initializing` will take care of the cleanup. + initializing.push(element_ref.clone()); + } + // If we reach here, then the entire slice is initialized, and we've satisfied our + // responsibilities to the caller. Disarm the cleanup guard by forgetting it. + mem::forget(initializing); + } +} + +// Specialized implementation for types that are [`Copy`], not just [`Clone`], +// and can therefore be copied bitwise. +unsafe impl CopySpec for T { + #[inline] + unsafe fn clone_one(src: &Self, dst: *mut Self) { + // SAFETY: The safety conditions of clone_to_uninit() are a superset of those of + // ptr::copy_nonoverlapping(). + unsafe { + ptr::copy_nonoverlapping(src, dst, 1); + } + } + + #[inline] + #[cfg_attr(debug_assertions, track_caller)] + unsafe fn clone_slice(src: &[Self], dst: *mut [Self]) { + let len = src.len(); + // This is the most likely mistake to make, so check it as a debug assertion. + debug_assert_eq!( + len, + dst.len(), + "clone_to_uninit() source and destination must have equal lengths", + ); + + // SAFETY: The safety conditions of clone_to_uninit() are a superset of those of + // ptr::copy_nonoverlapping(). + unsafe { + ptr::copy_nonoverlapping(src.as_ptr(), dst.as_mut_ptr(), len); + } + } +} + +/// Ownership of a collection of values stored in a non-owned `[MaybeUninit]`, some of which +/// are not yet initialized. This is sort of like a `Vec` that doesn't own its allocation. +/// Its responsibility is to provide cleanup on unwind by dropping the values that *are* +/// initialized, unless disarmed by forgetting. +/// +/// This is a helper for `impl CloneToUninit for [T]`. +struct InitializingSlice<'a, T> { + data: &'a mut [MaybeUninit], + /// Number of elements of `*self.data` that are initialized. + initialized_len: usize, +} + +impl<'a, T> InitializingSlice<'a, T> { + #[inline] + fn from_fully_uninit(data: &'a mut [MaybeUninit]) -> Self { + Self { data, initialized_len: 0 } + } + + /// Push a value onto the end of the initialized part of the slice. + /// + /// # Panics + /// + /// Panics if the slice is already fully initialized. + #[inline] + fn push(&mut self, value: T) { + MaybeUninit::write(&mut self.data[self.initialized_len], value); + self.initialized_len += 1; + } +} + +impl<'a, T> Drop for InitializingSlice<'a, T> { + #[cold] // will only be invoked on unwind + fn drop(&mut self) { + let initialized_slice = ptr::slice_from_raw_parts_mut( + MaybeUninit::slice_as_mut_ptr(self.data), + self.initialized_len, + ); + // SAFETY: + // * the pointer is valid because it was made from a mutable reference + // * `initialized_len` counts the initialized elements as an invariant of this type, + // so each of the pointed-to elements is initialized and may be dropped. + unsafe { + ptr::drop_in_place::<[T]>(initialized_slice); + } + } +} From 0732f7d5e1ea2b735db98d53b628e512f8d5a372 Mon Sep 17 00:00:00 2001 From: daxpedda Date: Sun, 8 Oct 2023 10:54:15 +0200 Subject: [PATCH 5/7] Stabilize `Ready::into_inner()` --- library/core/src/future/ready.rs | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/library/core/src/future/ready.rs b/library/core/src/future/ready.rs index a07b63fb62b90..6f6da8ce51ddf 100644 --- a/library/core/src/future/ready.rs +++ b/library/core/src/future/ready.rs @@ -34,13 +34,12 @@ impl Ready { /// # Examples /// /// ``` - /// #![feature(ready_into_inner)] /// use std::future; /// /// let a = future::ready(1); /// assert_eq!(a.into_inner(), 1); /// ``` - #[unstable(feature = "ready_into_inner", issue = "101196")] + #[stable(feature = "ready_into_inner", since = "CURRENT_RUSTC_VERSION")] #[must_use] #[inline] pub fn into_inner(self) -> T { From 29017e45a1c85afe457765a5d4c77e4fcdebb4f6 Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Fri, 16 Aug 2024 12:42:02 -0700 Subject: [PATCH 6/7] mir/pretty: use `Option` instead of `Either` `Either` is wasteful for a one-or-none iterator, especially since `Once` is already an `option::IntoIter` internally. We don't really need any of the iterator mechanisms in this case, just a single conditional insert. --- compiler/rustc_middle/src/mir/pretty.rs | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs index f2d8781413096..5dd0e69cf1fe6 100644 --- a/compiler/rustc_middle/src/mir/pretty.rs +++ b/compiler/rustc_middle/src/mir/pretty.rs @@ -1418,21 +1418,19 @@ pub fn write_allocations<'tcx>( alloc.inner().provenance().ptrs().values().map(|p| p.alloc_id()) } - fn alloc_ids_from_const_val(val: ConstValue<'_>) -> impl Iterator + '_ { + fn alloc_id_from_const_val(val: ConstValue<'_>) -> Option { match val { - ConstValue::Scalar(interpret::Scalar::Ptr(ptr, _)) => { - Either::Left(std::iter::once(ptr.provenance.alloc_id())) - } - ConstValue::Scalar(interpret::Scalar::Int { .. }) => Either::Right(std::iter::empty()), - ConstValue::ZeroSized => Either::Right(std::iter::empty()), + ConstValue::Scalar(interpret::Scalar::Ptr(ptr, _)) => Some(ptr.provenance.alloc_id()), + ConstValue::Scalar(interpret::Scalar::Int { .. }) => None, + ConstValue::ZeroSized => None, ConstValue::Slice { .. } => { // `u8`/`str` slices, shouldn't contain pointers that we want to print. - Either::Right(std::iter::empty()) + None } ConstValue::Indirect { alloc_id, .. } => { // FIXME: we don't actually want to print all of these, since some are printed nicely directly as values inline in MIR. // Really we'd want `pretty_print_const_value` to decide which allocations to print, instead of having a separate visitor. - Either::Left(std::iter::once(alloc_id)) + Some(alloc_id) } } } @@ -1443,7 +1441,9 @@ pub fn write_allocations<'tcx>( match c.const_ { Const::Ty(_, _) | Const::Unevaluated(..) => {} Const::Val(val, _) => { - self.0.extend(alloc_ids_from_const_val(val)); + if let Some(id) = alloc_id_from_const_val(val) { + self.0.insert(id); + } } } } From ed6315b3fef4ebd9aee053d407eb746c3b1d58bf Mon Sep 17 00:00:00 2001 From: Boxy Date: Fri, 16 Aug 2024 20:53:02 +0100 Subject: [PATCH 7/7] Rewrite `get_fn_id_for_return_block` --- compiler/rustc_middle/src/hir/map/mod.rs | 64 +++++----- tests/crashes/128810.rs | 25 ---- ..._body_owner_parent_found_in_diagnostics.rs | 34 ++++++ ...y_owner_parent_found_in_diagnostics.stderr | 113 ++++++++++++++++++ tests/ui/typeck/const-in-fn-call-generics.rs | 16 +++ .../typeck/const-in-fn-call-generics.stderr | 9 ++ 6 files changed, 199 insertions(+), 62 deletions(-) delete mode 100644 tests/crashes/128810.rs create mode 100644 tests/ui/delegation/correct_body_owner_parent_found_in_diagnostics.rs create mode 100644 tests/ui/delegation/correct_body_owner_parent_found_in_diagnostics.stderr create mode 100644 tests/ui/typeck/const-in-fn-call-generics.rs create mode 100644 tests/ui/typeck/const-in-fn-call-generics.stderr diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs index edab6b5ebde84..da08027d66b19 100644 --- a/compiler/rustc_middle/src/hir/map/mod.rs +++ b/compiler/rustc_middle/src/hir/map/mod.rs @@ -554,53 +554,43 @@ impl<'hir> Map<'hir> { /// } /// ``` pub fn get_fn_id_for_return_block(self, id: HirId) -> Option { - let mut iter = self.parent_iter(id).peekable(); - let mut ignore_tail = false; - if let Node::Expr(Expr { kind: ExprKind::Ret(_), .. }) = self.tcx.hir_node(id) { - // When dealing with `return` statements, we don't care about climbing only tail - // expressions. - ignore_tail = true; - } + let enclosing_body_owner = self.tcx.local_def_id_to_hir_id(self.enclosing_body_owner(id)); + + // Return `None` if the `id` expression is not the returned value of the enclosing body + let mut iter = [id].into_iter().chain(self.parent_id_iter(id)).peekable(); + while let Some(cur_id) = iter.next() { + if enclosing_body_owner == cur_id { + break; + } + + // A return statement is always the value returned from the enclosing body regardless of + // what the parent expressions are. + if let Node::Expr(Expr { kind: ExprKind::Ret(_), .. }) = self.tcx.hir_node(cur_id) { + break; + } - let mut prev_hir_id = None; - while let Some((hir_id, node)) = iter.next() { - if let (Some((_, next_node)), false) = (iter.peek(), ignore_tail) { - match next_node { - Node::Block(Block { expr: None, .. }) => return None, - // The current node is not the tail expression of its parent. - Node::Block(Block { expr: Some(e), .. }) if hir_id != e.hir_id => return None, + // If the current expression's value doesnt get used as the parent expressions value then return `None` + if let Some(&parent_id) = iter.peek() { + match self.tcx.hir_node(parent_id) { + // The current node is not the tail expression of the block expression parent expr. + Node::Block(Block { expr: Some(e), .. }) if cur_id != e.hir_id => return None, Node::Block(Block { expr: Some(e), .. }) if matches!(e.kind, ExprKind::If(_, _, None)) => { return None; } + + // The current expression's value does not pass up through these parent expressions + Node::Block(Block { expr: None, .. }) + | Node::Expr(Expr { kind: ExprKind::Loop(..), .. }) + | Node::LetStmt(..) => return None, + _ => {} } } - match node { - Node::Item(_) - | Node::ForeignItem(_) - | Node::TraitItem(_) - | Node::Expr(Expr { kind: ExprKind::Closure(_), .. }) - | Node::ImplItem(_) - // The input node `id` must be enclosed in the method's body as opposed - // to some other place such as its return type (fixes #114918). - // We verify that indirectly by checking that the previous node is the - // current node's body - if node.body_id().map(|b| b.hir_id) == prev_hir_id => { - return Some(hir_id) - } - // Ignore `return`s on the first iteration - Node::Expr(Expr { kind: ExprKind::Loop(..) | ExprKind::Ret(..), .. }) - | Node::LetStmt(_) => { - return None; - } - _ => {} - } - - prev_hir_id = Some(hir_id); } - None + + Some(enclosing_body_owner) } /// Retrieves the `OwnerId` for `id`'s parent item, or `id` itself if no diff --git a/tests/crashes/128810.rs b/tests/crashes/128810.rs deleted file mode 100644 index 68214ff010c99..0000000000000 --- a/tests/crashes/128810.rs +++ /dev/null @@ -1,25 +0,0 @@ -//@ known-bug: rust-lang/rust#128810 - -#![feature(fn_delegation)] - -use std::marker::PhantomData; - -pub struct InvariantRef<'a, T: ?Sized>(&'a T, PhantomData<&'a mut &'a T>); - -impl<'a> InvariantRef<'a, ()> { - pub const NEW: Self = InvariantRef::new(&()); -} - -trait Trait { - fn foo(&self) -> u8 { 0 } - fn bar(&self) -> u8 { 1 } - fn meh(&self) -> u8 { 2 } -} - -struct Z(u8); - -impl Trait for Z { - reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } -} - -fn main() { } diff --git a/tests/ui/delegation/correct_body_owner_parent_found_in_diagnostics.rs b/tests/ui/delegation/correct_body_owner_parent_found_in_diagnostics.rs new file mode 100644 index 0000000000000..0a7ec5ab5c1be --- /dev/null +++ b/tests/ui/delegation/correct_body_owner_parent_found_in_diagnostics.rs @@ -0,0 +1,34 @@ +#![feature(fn_delegation)] +#![allow(incomplete_features)] + +use std::marker::PhantomData; + +pub struct InvariantRef<'a, T: ?Sized>(&'a T, PhantomData<&'a mut &'a T>); + +impl<'a> InvariantRef<'a, ()> { + pub const NEW: Self = InvariantRef::new(&()); + //~^ ERROR: no function or associated item named `new` found +} + +trait Trait { + fn foo(&self) -> u8 { 0 } + fn bar(&self) -> u8 { 1 } + fn meh(&self) -> u8 { 2 } +} + +struct Z(u8); + +impl Trait for Z { + reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } + //~^ ERROR: use of undeclared lifetime name `'a` + //~| ERROR: use of undeclared lifetime name `'a` + //~| ERROR: use of undeclared lifetime name `'a` + //~| ERROR: the trait bound `u8: Trait` is not satisfied + //~| ERROR: the trait bound `u8: Trait` is not satisfied + //~| ERROR: the trait bound `u8: Trait` is not satisfied + //~| ERROR: mismatched types + //~| ERROR: mismatched types + //~| ERROR: mismatched types +} + +fn main() { } diff --git a/tests/ui/delegation/correct_body_owner_parent_found_in_diagnostics.stderr b/tests/ui/delegation/correct_body_owner_parent_found_in_diagnostics.stderr new file mode 100644 index 0000000000000..2ce3b388073c4 --- /dev/null +++ b/tests/ui/delegation/correct_body_owner_parent_found_in_diagnostics.stderr @@ -0,0 +1,113 @@ +error[E0261]: use of undeclared lifetime name `'a` + --> $DIR/correct_body_owner_parent_found_in_diagnostics.rs:22:68 + | +LL | reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } + | ^^ undeclared lifetime + | +help: consider introducing lifetime `'a` here + | +LL | reuse ::{foo'a, , bar, meh} { &const { InvariantRef::<'a>::NEW } } + | +++ +help: consider introducing lifetime `'a` here + | +LL | impl<'a> Trait for Z { + | ++++ + +error[E0261]: use of undeclared lifetime name `'a` + --> $DIR/correct_body_owner_parent_found_in_diagnostics.rs:22:68 + | +LL | reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } + | ^^ undeclared lifetime + | +help: consider introducing lifetime `'a` here + | +LL | reuse ::{foo, bar'a, , meh} { &const { InvariantRef::<'a>::NEW } } + | +++ +help: consider introducing lifetime `'a` here + | +LL | impl<'a> Trait for Z { + | ++++ + +error[E0261]: use of undeclared lifetime name `'a` + --> $DIR/correct_body_owner_parent_found_in_diagnostics.rs:22:68 + | +LL | reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } + | ^^ undeclared lifetime + | +help: consider introducing lifetime `'a` here + | +LL | reuse ::{foo, bar, meh'a, } { &const { InvariantRef::<'a>::NEW } } + | +++ +help: consider introducing lifetime `'a` here + | +LL | impl<'a> Trait for Z { + | ++++ + +error[E0599]: no function or associated item named `new` found for struct `InvariantRef` in the current scope + --> $DIR/correct_body_owner_parent_found_in_diagnostics.rs:9:41 + | +LL | pub struct InvariantRef<'a, T: ?Sized>(&'a T, PhantomData<&'a mut &'a T>); + | -------------------------------------- function or associated item `new` not found for this struct +... +LL | pub const NEW: Self = InvariantRef::new(&()); + | ^^^ function or associated item not found in `InvariantRef<'_, _>` + +error[E0308]: mismatched types + --> $DIR/correct_body_owner_parent_found_in_diagnostics.rs:22:53 + | +LL | reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } + | ^^^^^^^^^^^^^^^^^^^^^^^ expected `u8`, found `InvariantRef<'_, ()>` + | + = note: expected type `u8` + found struct `InvariantRef<'_, ()>` + +error[E0277]: the trait bound `u8: Trait` is not satisfied + --> $DIR/correct_body_owner_parent_found_in_diagnostics.rs:22:12 + | +LL | reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } + | ^^ the trait `Trait` is not implemented for `u8` + | + = help: the trait `Trait` is implemented for `Z` + +error[E0308]: mismatched types + --> $DIR/correct_body_owner_parent_found_in_diagnostics.rs:22:53 + | +LL | reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } + | ^^^^^^^^^^^^^^^^^^^^^^^ expected `u8`, found `InvariantRef<'_, ()>` + | + = note: expected type `u8` + found struct `InvariantRef<'_, ()>` + = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no` + +error[E0277]: the trait bound `u8: Trait` is not satisfied + --> $DIR/correct_body_owner_parent_found_in_diagnostics.rs:22:12 + | +LL | reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } + | ^^ the trait `Trait` is not implemented for `u8` + | + = help: the trait `Trait` is implemented for `Z` + = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no` + +error[E0308]: mismatched types + --> $DIR/correct_body_owner_parent_found_in_diagnostics.rs:22:53 + | +LL | reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } + | ^^^^^^^^^^^^^^^^^^^^^^^ expected `u8`, found `InvariantRef<'_, ()>` + | + = note: expected type `u8` + found struct `InvariantRef<'_, ()>` + = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no` + +error[E0277]: the trait bound `u8: Trait` is not satisfied + --> $DIR/correct_body_owner_parent_found_in_diagnostics.rs:22:12 + | +LL | reuse ::{foo, bar, meh} { &const { InvariantRef::<'a>::NEW } } + | ^^ the trait `Trait` is not implemented for `u8` + | + = help: the trait `Trait` is implemented for `Z` + = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no` + +error: aborting due to 10 previous errors + +Some errors have detailed explanations: E0261, E0277, E0308, E0599. +For more information about an error, try `rustc --explain E0261`. diff --git a/tests/ui/typeck/const-in-fn-call-generics.rs b/tests/ui/typeck/const-in-fn-call-generics.rs new file mode 100644 index 0000000000000..675dbcc305475 --- /dev/null +++ b/tests/ui/typeck/const-in-fn-call-generics.rs @@ -0,0 +1,16 @@ +fn generic() {} + +trait Collate { + type Pass; + fn collate(self) -> Self::Pass; +} + +impl Collate for i32 { + type Pass = (); + fn collate(self) -> Self::Pass { + generic::<{ true }>() + //~^ ERROR: mismatched types + } +} + +fn main() {} diff --git a/tests/ui/typeck/const-in-fn-call-generics.stderr b/tests/ui/typeck/const-in-fn-call-generics.stderr new file mode 100644 index 0000000000000..12dd454188cac --- /dev/null +++ b/tests/ui/typeck/const-in-fn-call-generics.stderr @@ -0,0 +1,9 @@ +error[E0308]: mismatched types + --> $DIR/const-in-fn-call-generics.rs:11:21 + | +LL | generic::<{ true }>() + | ^^^^ expected `u32`, found `bool` + +error: aborting due to 1 previous error + +For more information about this error, try `rustc --explain E0308`.