alloc: Add unstable Cfg feature no-global_oom_handling
For certain sorts of systems, programming, it's deemed essential that all allocation failures be explicitly handled where they occur. For example, see Linus Torvald's opinion in [1]. Merely not calling global panic handlers, or always `try_reserving` first (for vectors), is not deemed good enough, because the mere presence of the global OOM handlers is burdens static analysis. One option for these projects to use rust would just be to skip `alloc`, rolling their own allocation abstractions. But this would, in my opinion be a real shame. `alloc` has a few `try_*` methods already, and we could easily have more. Features like custom allocator support also demonstrate and existing to support diverse use-cases with the same abstractions. A natural way to add such a feature flag would a Cargo feature, but there are currently uncertainties around how std library crate's Cargo features may or not be stable, so to avoid any risk of stabilizing by mistake we are going with a more low-level "raw cfg" token, which cannot be interacted with via Cargo alone. Note also that since there is no notion of "default cfg tokens" outside of Cargo features, we have to invert the condition from `global_oom_handling` to to `not(no_global_oom_handling)`. This breaks the monotonicity that would be important for a Cargo feature (i.e. turning on more features should never break compatibility), but it doesn't matter for raw cfg tokens which are not intended to be "constraint solved" by Cargo or anything else. To support this use-case we create a new feature, "global-oom-handling", on by default, and put the global OOM handler infra and everything else it that depends on it behind it. By default, nothing is changed, but users concerned about global handling can make sure it is disabled, and be confident that all OOM handling is local and explicit. For this first iteration, non-flat collections are outright disabled. `Vec` and `String` don't yet have `try_*` allocation methods, but are kept anyways since they can be oom-safely created "from parts", and we hope to add those `try_` methods in the future. [1]: https://lore.kernel.org/lkml/CAHk-=wh_sNLoz84AUUzuqXEsYH35u=8HV3vK-jbRbJ_B-JjGrg@mail.gmail.com/
This commit is contained in:
John Ericson
parent
3ec0baa8bc
commit
19be438cda
16 changed files with 326 additions and 27 deletions
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@ -53,12 +53,16 @@
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#![stable(feature = "rust1", since = "1.0.0")]
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use core::cmp::{self, Ordering};
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#[cfg(not(no_global_oom_handling))]
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use core::cmp;
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use core::cmp::Ordering;
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use core::convert::TryFrom;
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use core::fmt;
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use core::hash::{Hash, Hasher};
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use core::intrinsics::{arith_offset, assume};
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use core::iter::{self, FromIterator};
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use core::iter;
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#[cfg(not(no_global_oom_handling))]
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use core::iter::FromIterator;
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use core::marker::PhantomData;
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use core::mem::{self, ManuallyDrop, MaybeUninit};
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use core::ops::{self, Index, IndexMut, Range, RangeBounds};
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@ -76,9 +80,11 @@ pub use self::drain_filter::DrainFilter;
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mod drain_filter;
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "vec_splice", since = "1.21.0")]
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pub use self::splice::Splice;
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#[cfg(not(no_global_oom_handling))]
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mod splice;
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#[stable(feature = "drain", since = "1.6.0")]
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@ -86,44 +92,60 @@ pub use self::drain::Drain;
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mod drain;
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#[cfg(not(no_global_oom_handling))]
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mod cow;
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#[cfg(not(no_global_oom_handling))]
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pub(crate) use self::into_iter::AsIntoIter;
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#[stable(feature = "rust1", since = "1.0.0")]
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pub use self::into_iter::IntoIter;
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mod into_iter;
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#[cfg(not(no_global_oom_handling))]
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use self::is_zero::IsZero;
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mod is_zero;
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#[cfg(not(no_global_oom_handling))]
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mod source_iter_marker;
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mod partial_eq;
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#[cfg(not(no_global_oom_handling))]
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use self::spec_from_elem::SpecFromElem;
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#[cfg(not(no_global_oom_handling))]
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mod spec_from_elem;
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#[cfg(not(no_global_oom_handling))]
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use self::set_len_on_drop::SetLenOnDrop;
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#[cfg(not(no_global_oom_handling))]
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mod set_len_on_drop;
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#[cfg(not(no_global_oom_handling))]
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use self::in_place_drop::InPlaceDrop;
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#[cfg(not(no_global_oom_handling))]
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mod in_place_drop;
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#[cfg(not(no_global_oom_handling))]
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use self::spec_from_iter_nested::SpecFromIterNested;
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#[cfg(not(no_global_oom_handling))]
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mod spec_from_iter_nested;
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#[cfg(not(no_global_oom_handling))]
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use self::spec_from_iter::SpecFromIter;
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#[cfg(not(no_global_oom_handling))]
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mod spec_from_iter;
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#[cfg(not(no_global_oom_handling))]
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use self::spec_extend::SpecExtend;
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#[cfg(not(no_global_oom_handling))]
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mod spec_extend;
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/// A contiguous growable array type, written as `Vec<T>` and pronounced 'vector'.
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@ -435,6 +457,7 @@ impl<T> Vec<T> {
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/// assert_eq!(vec.len(), 11);
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/// assert!(vec.capacity() >= 11);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[inline]
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#[doc(alias = "malloc")]
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#[stable(feature = "rust1", since = "1.0.0")]
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@ -574,6 +597,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// assert_eq!(vec.len(), 11);
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/// assert!(vec.capacity() >= 11);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[inline]
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#[unstable(feature = "allocator_api", issue = "32838")]
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pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
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@ -774,6 +798,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// vec.reserve(10);
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/// assert!(vec.capacity() >= 11);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[doc(alias = "realloc")]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn reserve(&mut self, additional: usize) {
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@ -800,6 +825,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// vec.reserve_exact(10);
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/// assert!(vec.capacity() >= 11);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[doc(alias = "realloc")]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn reserve_exact(&mut self, additional: usize) {
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@ -900,6 +926,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// vec.shrink_to_fit();
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/// assert!(vec.capacity() >= 3);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[doc(alias = "realloc")]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn shrink_to_fit(&mut self) {
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@ -930,6 +957,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// vec.shrink_to(0);
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/// assert!(vec.capacity() >= 3);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[doc(alias = "realloc")]
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#[unstable(feature = "shrink_to", reason = "new API", issue = "56431")]
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pub fn shrink_to(&mut self, min_capacity: usize) {
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@ -962,6 +990,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// let slice = vec.into_boxed_slice();
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/// assert_eq!(slice.into_vec().capacity(), 3);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn into_boxed_slice(mut self) -> Box<[T], A> {
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unsafe {
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@ -1299,6 +1328,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// vec.insert(4, 5);
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/// assert_eq!(vec, [1, 4, 2, 3, 5]);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn insert(&mut self, index: usize, element: T) {
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#[cold]
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@ -1627,6 +1657,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// vec.push(3);
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/// assert_eq!(vec, [1, 2, 3]);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[inline]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn push(&mut self, value: T) {
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@ -1680,6 +1711,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// assert_eq!(vec, [1, 2, 3, 4, 5, 6]);
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/// assert_eq!(vec2, []);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[inline]
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#[stable(feature = "append", since = "1.4.0")]
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pub fn append(&mut self, other: &mut Self) {
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@ -1690,6 +1722,7 @@ impl<T, A: Allocator> Vec<T, A> {
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}
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/// Appends elements to `Self` from other buffer.
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#[cfg(not(no_global_oom_handling))]
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#[inline]
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unsafe fn append_elements(&mut self, other: *const [T]) {
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let count = unsafe { (*other).len() };
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@ -1827,6 +1860,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// assert_eq!(vec, [1]);
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/// assert_eq!(vec2, [2, 3]);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[inline]
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#[must_use = "use `.truncate()` if you don't need the other half"]
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#[stable(feature = "split_off", since = "1.4.0")]
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@ -1891,6 +1925,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// vec.resize_with(4, || { p *= 2; p });
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/// assert_eq!(vec, [2, 4, 8, 16]);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "vec_resize_with", since = "1.33.0")]
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pub fn resize_with<F>(&mut self, new_len: usize, f: F)
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where
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@ -1926,6 +1961,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// static_ref[0] += 1;
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/// assert_eq!(static_ref, &[2, 2, 3]);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "vec_leak", since = "1.47.0")]
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#[inline]
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pub fn leak<'a>(self) -> &'a mut [T]
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@ -2084,6 +2120,7 @@ impl<T: Clone, A: Allocator> Vec<T, A> {
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/// vec.resize(2, 0);
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/// assert_eq!(vec, [1, 2]);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "vec_resize", since = "1.5.0")]
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pub fn resize(&mut self, new_len: usize, value: T) {
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let len = self.len();
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/// ```
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///
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/// [`extend`]: Vec::extend
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "vec_extend_from_slice", since = "1.6.0")]
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pub fn extend_from_slice(&mut self, other: &[T]) {
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self.spec_extend(other.iter())
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/// vec.extend_from_within(4..8);
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/// assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1, 4, 2, 3, 4]);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "vec_extend_from_within", since = "1.53.0")]
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pub fn extend_from_within<R>(&mut self, src: R)
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where
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@ -2188,6 +2227,7 @@ impl<T, F: FnMut() -> T> ExtendWith<T> for ExtendFunc<F> {
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}
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impl<T, A: Allocator> Vec<T, A> {
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#[cfg(not(no_global_oom_handling))]
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/// Extend the vector by `n` values, using the given generator.
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fn extend_with<E: ExtendWith<T>>(&mut self, n: usize, mut value: E) {
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self.reserve(n);
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@ -2245,12 +2285,14 @@ impl<T: PartialEq, A: Allocator> Vec<T, A> {
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////////////////////////////////////////////////////////////////////////////////
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#[doc(hidden)]
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn from_elem<T: Clone>(elem: T, n: usize) -> Vec<T> {
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<T as SpecFromElem>::from_elem(elem, n, Global)
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}
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#[doc(hidden)]
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#[cfg(not(no_global_oom_handling))]
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#[unstable(feature = "allocator_api", issue = "32838")]
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pub fn from_elem_in<T: Clone, A: Allocator>(elem: T, n: usize, alloc: A) -> Vec<T, A> {
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<T as SpecFromElem>::from_elem(elem, n, alloc)
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@ -2331,6 +2373,7 @@ impl<T, A: Allocator> ops::DerefMut for Vec<T, A> {
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}
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}
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: Clone, A: Allocator + Clone> Clone for Vec<T, A> {
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#[cfg(not(test))]
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@ -2397,6 +2440,7 @@ impl<T, I: SliceIndex<[T]>, A: Allocator> IndexMut<I> for Vec<T, A> {
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}
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}
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T> FromIterator<T> for Vec<T> {
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#[inline]
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@ -2467,6 +2511,7 @@ impl<'a, T, A: Allocator> IntoIterator for &'a mut Vec<T, A> {
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}
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}
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T, A: Allocator> Extend<T> for Vec<T, A> {
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#[inline]
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@ -2488,6 +2533,7 @@ impl<T, A: Allocator> Extend<T> for Vec<T, A> {
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impl<T, A: Allocator> Vec<T, A> {
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// leaf method to which various SpecFrom/SpecExtend implementations delegate when
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// they have no further optimizations to apply
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#[cfg(not(no_global_oom_handling))]
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fn extend_desugared<I: Iterator<Item = T>>(&mut self, mut iterator: I) {
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// This is the case for a general iterator.
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//
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@ -2543,6 +2589,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// assert_eq!(v, &[7, 8, 3]);
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/// assert_eq!(u, &[1, 2]);
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/// ```
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#[cfg(not(no_global_oom_handling))]
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#[inline]
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#[stable(feature = "vec_splice", since = "1.21.0")]
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pub fn splice<R, I>(&mut self, range: R, replace_with: I) -> Splice<'_, I::IntoIter, A>
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@ -2619,6 +2666,7 @@ impl<T, A: Allocator> Vec<T, A> {
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/// append the entire slice at once.
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///
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/// [`copy_from_slice`]: slice::copy_from_slice
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "extend_ref", since = "1.2.0")]
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impl<'a, T: Copy + 'a, A: Allocator + 'a> Extend<&'a T> for Vec<T, A> {
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fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
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@ -2713,6 +2761,7 @@ impl<T, A: Allocator> AsMut<[T]> for Vec<T, A> {
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}
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}
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: Clone> From<&[T]> for Vec<T> {
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/// Allocate a `Vec<T>` and fill it by cloning `s`'s items.
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@ -2732,6 +2781,7 @@ impl<T: Clone> From<&[T]> for Vec<T> {
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}
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}
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "vec_from_mut", since = "1.19.0")]
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impl<T: Clone> From<&mut [T]> for Vec<T> {
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/// Allocate a `Vec<T>` and fill it by cloning `s`'s items.
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@ -2813,6 +2863,7 @@ impl<T, A: Allocator> From<Box<[T], A>> for Vec<T, A> {
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}
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// note: test pulls in libstd, which causes errors here
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#[cfg(not(no_global_oom_handling))]
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#[cfg(not(test))]
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#[stable(feature = "box_from_vec", since = "1.20.0")]
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impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A> {
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@ -2831,6 +2882,7 @@ impl<T, A: Allocator> From<Vec<T, A>> for Box<[T], A> {
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}
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}
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#[cfg(not(no_global_oom_handling))]
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#[stable(feature = "rust1", since = "1.0.0")]
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impl From<&str> for Vec<u8> {
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/// Allocate a `Vec<u8>` and fill it with a UTF-8 string.
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