Support 3 allocator schemes

nightly - unstable allocator_api
allocator-api2 - stable version of allocator_api
neither - custom trait implemented only for default allocator parameter

Author: zakarumych

Cargo.toml

@@ -39,10 +39,13 @@ doc-comment = "0.3.1"
 [features]
 default = ["ahash", "inline-more", "allocator-api2"]
 
-nightly = []
+nightly-base = [] # non-public feature to use nightly features without depending on `allocator-api2`
+
+nightly = ["allocator-api2/nightly", "nightly-base"]
+
 rustc-internal-api = []
 rustc-dep-of-std = [
-    "nightly",
+    "nightly-base",
     "core",
     "compiler_builtins",
     "alloc",

ci/tools.sh

@@ -30,7 +30,7 @@ if retry rustup component add rustfmt ; then
 fi
 
 if retry rustup component add clippy ; then
-    cargo clippy --all --tests --features serde,rayon,bumpalo -- -D clippy::all
+    cargo clippy --all --tests --features serde,rayon -- -D clippy::all
     cargo clippy --all --tests --features raw -- -D clippy::all
 fi
 

src/lib.rs

@@ -11,7 +11,7 @@
 
 #![no_std]
 #![cfg_attr(
-    feature = "nightly",
+    feature = "nightly-base",
     feature(
         test,
         core_intrinsics,
@@ -37,7 +37,7 @@
 )]
 #![warn(missing_docs)]
 #![warn(rust_2018_idioms)]
-#![cfg_attr(feature = "nightly", warn(fuzzy_provenance_casts))]
+#![cfg_attr(feature = "nightly-base", warn(fuzzy_provenance_casts))]
 
 #[cfg(test)]
 #[macro_use]
@@ -46,7 +46,7 @@ extern crate std;
 #[cfg_attr(test, macro_use)]
 extern crate alloc;
 
-#[cfg(feature = "nightly")]
+#[cfg(feature = "nightly-base")]
 #[cfg(doctest)]
 doc_comment::doctest!("../README.md");
 

src/macros.rs

@@ -56,13 +56,13 @@ macro_rules! cfg_if {
 
 // Helper macro for specialization. This also helps avoid parse errors if the
 // default fn syntax for specialization changes in the future.
-#[cfg(feature = "nightly")]
+#[cfg(feature = "nightly-base")]
 macro_rules! default_fn {
 	(#[$($a:tt)*] $($tt:tt)*) => {
         #[$($a)*] default $($tt)*
     }
 }
-#[cfg(not(feature = "nightly"))]
+#[cfg(not(feature = "nightly-base"))]
 macro_rules! default_fn {
 	($($tt:tt)*) => {
         $($tt)*

src/map.rs

@@ -237,7 +237,7 @@ where
     move |x| k.equivalent(x)
 }
 
-#[cfg(not(feature = "nightly"))]
+#[cfg(not(feature = "nightly-base"))]
 #[cfg_attr(feature = "inline-more", inline)]
 pub(crate) fn make_hash<Q, S>(hash_builder: &S, val: &Q) -> u64
 where
@@ -250,7 +250,7 @@ where
     state.finish()
 }
 
-#[cfg(feature = "nightly")]
+#[cfg(feature = "nightly-base")]
 #[cfg_attr(feature = "inline-more", inline)]
 pub(crate) fn make_hash<Q, S>(hash_builder: &S, val: &Q) -> u64
 where
@@ -260,7 +260,7 @@ where
     hash_builder.hash_one(val)
 }
 
-#[cfg(not(feature = "nightly"))]
+#[cfg(not(feature = "nightly-base"))]
 #[cfg_attr(feature = "inline-more", inline)]
 pub(crate) fn make_insert_hash<K, S>(hash_builder: &S, val: &K) -> u64
 where
@@ -273,7 +273,7 @@ where
     state.finish()
 }
 
-#[cfg(feature = "nightly")]
+#[cfg(feature = "nightly-base")]
 #[cfg_attr(feature = "inline-more", inline)]
 pub(crate) fn make_insert_hash<K, S>(hash_builder: &S, val: &K) -> u64
 where
@@ -6498,13 +6498,13 @@ where
     }
 
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     fn extend_one(&mut self, (k, v): (K, V)) {
         self.insert(k, v);
     }
 
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     fn extend_reserve(&mut self, additional: usize) {
         // Keys may be already present or show multiple times in the iterator.
         // Reserve the entire hint lower bound if the map is empty.
@@ -6572,13 +6572,13 @@ where
     }
 
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     fn extend_one(&mut self, (k, v): (&'a K, &'a V)) {
         self.insert(*k, *v);
     }
 
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     fn extend_reserve(&mut self, additional: usize) {
         Extend::<(K, V)>::extend_reserve(self, additional);
     }
@@ -6632,13 +6632,13 @@ where
     }
 
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     fn extend_one(&mut self, &(k, v): &'a (K, V)) {
         self.insert(k, v);
     }
 
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     fn extend_reserve(&mut self, additional: usize) {
         Extend::<(K, V)>::extend_reserve(self, additional);
     }

src/raw/alloc.rs

@@ -1,6 +1,10 @@
 pub(crate) use self::inner::{do_alloc, Allocator, Global};
 
-#[cfg(feature = "nightly")]
+// Nightly-case.
+// Use unstable `allocator_api` feature.
+// This is compatible with `allocator-api2` which can be enabled or not.
+// This is used when building for `std`.
+#[cfg(feature = "nightly-base")]
 mod inner {
     use crate::alloc::alloc::Layout;
     pub use crate::alloc::alloc::{Allocator, Global};
@@ -15,7 +19,13 @@ mod inner {
     }
 }
 
-#[cfg(not(feature = "nightly"))]
+// Basic non-nightly case.
+// This uses `allocator-api2` enabled by default.
+// If any crate enables "nightly" in `allocator-api2`,
+// this will be equivalent to the nightly case,
+// since `allocator_api2::alloc::Allocator` would be re-export of
+// `core::alloc::Allocator`.
+#[cfg(all(not(feature = "nightly-base"), feature = "allocator-api2"))]
 mod inner {
     use crate::alloc::alloc::Layout;
     pub use allocator_api2::alloc::{Allocator, Global};
@@ -29,3 +39,48 @@ mod inner {
         }
     }
 }
+
+// No-defaults case.
+// When building with default-features turned off and
+// neither `nightly` nor `allocator-api2` is enabled,
+// this will be used.
+// Making it impossible to use any custom allocator with collections defined
+// in this crate.
+// Any crate in build-tree can enable `allocator-api2`,
+// or `nightly` without disturbing users that don't want to use it.
+#[cfg(not(any(feature = "nightly-base", feature = "allocator-api2")))]
+mod inner {
+    use crate::alloc::alloc::{alloc, dealloc, Layout};
+    use core::ptr::NonNull;
+
+    #[allow(clippy::missing_safety_doc)] // not exposed outside of this crate
+    pub unsafe trait Allocator {
+        fn allocate(&self, layout: Layout) -> Result<NonNull<u8>, ()>;
+        unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout);
+    }
+
+    #[derive(Copy, Clone)]
+    pub struct Global;
+
+    unsafe impl Allocator for Global {
+        #[inline]
+        fn allocate(&self, layout: Layout) -> Result<NonNull<u8>, ()> {
+            unsafe { NonNull::new(alloc(layout)).ok_or(()) }
+        }
+        #[inline]
+        unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
+            dealloc(ptr.as_ptr(), layout);
+        }
+    }
+
+    impl Default for Global {
+        #[inline]
+        fn default() -> Self {
+            Global
+        }
+    }
+
+    pub(crate) fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<u8>, ()> {
+        alloc.allocate(layout)
+    }
+}

src/raw/bitmask.rs

@@ -1,5 +1,5 @@
 use super::imp::{BitMaskWord, BITMASK_MASK, BITMASK_STRIDE};
-#[cfg(feature = "nightly")]
+#[cfg(feature = "nightly-base")]
 use core::intrinsics;
 
 /// A bit mask which contains the result of a `Match` operation on a `Group` and
@@ -64,12 +64,12 @@ impl BitMask {
     /// Returns the first set bit in the `BitMask`, if there is one. The
     /// bitmask must not be empty.
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     pub(crate) unsafe fn lowest_set_bit_nonzero(self) -> usize {
         intrinsics::cttz_nonzero(self.0) as usize / BITMASK_STRIDE
     }
     #[inline]
-    #[cfg(not(feature = "nightly"))]
+    #[cfg(not(feature = "nightly-base"))]
     pub(crate) unsafe fn lowest_set_bit_nonzero(self) -> usize {
         self.trailing_zeros()
     }

src/raw/mod.rs

@@ -42,25 +42,25 @@ use self::imp::Group;
 
 // Branch prediction hint. This is currently only available on nightly but it
 // consistently improves performance by 10-15%.
-#[cfg(feature = "nightly")]
+#[cfg(feature = "nightly-base")]
 use core::intrinsics::{likely, unlikely};
 
 // On stable we can use #[cold] to get a equivalent effect: this attributes
 // suggests that the function is unlikely to be called
-#[cfg(not(feature = "nightly"))]
+#[cfg(not(feature = "nightly-base"))]
 #[inline]
 #[cold]
 fn cold() {}
 
-#[cfg(not(feature = "nightly"))]
+#[cfg(not(feature = "nightly-base"))]
 #[inline]
 fn likely(b: bool) -> bool {
     if !b {
         cold();
     }
     b
 }
-#[cfg(not(feature = "nightly"))]
+#[cfg(not(feature = "nightly-base"))]
 #[inline]
 fn unlikely(b: bool) -> bool {
     if b {
@@ -70,10 +70,10 @@ fn unlikely(b: bool) -> bool {
 }
 
 // Use strict provenance functions if available.
-#[cfg(feature = "nightly")]
+#[cfg(feature = "nightly-base")]
 use core::ptr::invalid_mut;
 // Implement it with a cast otherwise.
-#[cfg(not(feature = "nightly"))]
+#[cfg(not(feature = "nightly-base"))]
 #[inline(always)]
 fn invalid_mut<T>(addr: usize) -> *mut T {
     addr as *mut T
@@ -936,7 +936,7 @@ impl<T, A: Allocator + Clone> RawTable<T, A> {
 
     /// Returns pointer to start of data table.
     #[inline]
-    #[cfg(any(feature = "raw", feature = "nightly"))]
+    #[cfg(any(feature = "raw", feature = "nightly-base"))]
     pub unsafe fn data_start(&self) -> NonNull<T> {
         NonNull::new_unchecked(self.data_end().as_ptr().wrapping_sub(self.buckets()))
     }
@@ -2562,7 +2562,7 @@ impl<T: Clone, A: Allocator + Clone> RawTableClone for RawTable<T, A> {
         }
     }
 }
-#[cfg(feature = "nightly")]
+#[cfg(feature = "nightly-base")]
 impl<T: Copy, A: Allocator + Clone> RawTableClone for RawTable<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     unsafe fn clone_from_spec(&mut self, source: &Self) {
@@ -2674,7 +2674,7 @@ impl<T, A: Allocator + Clone + Default> Default for RawTable<T, A> {
     }
 }
 
-#[cfg(feature = "nightly")]
+#[cfg(feature = "nightly-base")]
 unsafe impl<#[may_dangle] T, A: Allocator + Clone> Drop for RawTable<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn drop(&mut self) {
@@ -2686,7 +2686,7 @@ unsafe impl<#[may_dangle] T, A: Allocator + Clone> Drop for RawTable<T, A> {
         }
     }
 }
-#[cfg(not(feature = "nightly"))]
+#[cfg(not(feature = "nightly-base"))]
 impl<T, A: Allocator + Clone> Drop for RawTable<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn drop(&mut self) {
@@ -3081,7 +3081,7 @@ where
 {
 }
 
-#[cfg(feature = "nightly")]
+#[cfg(feature = "nightly-base")]
 unsafe impl<#[may_dangle] T, A: Allocator + Clone> Drop for RawIntoIter<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn drop(&mut self) {
@@ -3096,7 +3096,7 @@ unsafe impl<#[may_dangle] T, A: Allocator + Clone> Drop for RawIntoIter<T, A> {
         }
     }
 }
-#[cfg(not(feature = "nightly"))]
+#[cfg(not(feature = "nightly-base"))]
 impl<T, A: Allocator + Clone> Drop for RawIntoIter<T, A> {
     #[cfg_attr(feature = "inline-more", inline)]
     fn drop(&mut self) {

src/set.rs

@@ -1354,13 +1354,13 @@ where
     }
 
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     fn extend_one(&mut self, k: T) {
         self.map.insert(k, ());
     }
 
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     fn extend_reserve(&mut self, additional: usize) {
         Extend::<(T, ())>::extend_reserve(&mut self.map, additional);
     }
@@ -1378,13 +1378,13 @@ where
     }
 
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     fn extend_one(&mut self, k: &'a T) {
         self.map.insert(*k, ());
     }
 
     #[inline]
-    #[cfg(feature = "nightly")]
+    #[cfg(feature = "nightly-base")]
     fn extend_reserve(&mut self, additional: usize) {
         Extend::<(T, ())>::extend_reserve(&mut self.map, additional);
     }