Snap for 8191477 from b9ce3fd360024e04bff9e8b3ad89f8bd5825e128 to tm-frc-scheduling-release

Change-Id: I247f42c92d5c492c2ed4a8dc316c85a12c5c3ab7

14 files changed, 204 insertions, 118 deletions

diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
index 1d9c34d..1f53d5d 100644
--- a/.cargo_vcs_info.json
+++ b/.cargo_vcs_info.json
@@ -1,5 +1,5 @@
 {
   "git": {
-    "sha1": "d841a2028dc72b4e09739116f07e865db60f3690"
+    "sha1": "6d4cdd4daf9a897deef6cde9569f2fbf12c29bc5"
   }
 }
diff --git a/Android.bp b/Android.bp
index bba5b1e..1ded857 100644
--- a/Android.bp
+++ b/Android.bp
@@ -1,4 +1,4 @@
-// This file is generated by cargo2android.py --run --device --dependencies --tests.
+// This file is generated by cargo2android.py --config cargo2android.json.
 // Do not modify this file as changes will be overridden on upgrade.
 
 package {
@@ -39,48 +39,18 @@ license {
     ],
 }
 
-rust_defaults {
-    name: "crossbeam-epoch_defaults",
+rust_test {
+    name: "crossbeam-epoch_test_src_lib",
+    host_supported: true,
     crate_name: "crossbeam_epoch",
+    cargo_env_compat: true,
+    cargo_pkg_version: "0.9.5",
     srcs: ["src/lib.rs"],
     test_suites: ["general-tests"],
     auto_gen_config: true,
-    edition: "2018",
-    features: [
-        "alloc",
-        "default",
-        "lazy_static",
-        "std",
-    ],
-    rustlibs: [
-        "libcfg_if",
-        "libcrossbeam_utils",
-        "liblazy_static",
-        "libmemoffset",
-        "librand",
-        "libscopeguard",
-    ],
-}
-
-rust_test_host {
-    name: "crossbeam-epoch_host_test_src_lib",
-    defaults: ["crossbeam-epoch_defaults"],
     test_options: {
         unit_test: true,
     },
-}
-
-rust_test {
-    name: "crossbeam-epoch_device_test_src_lib",
-    defaults: ["crossbeam-epoch_defaults"],
-}
-
-rust_defaults {
-    name: "crossbeam-epoch_defaults_loom",
-    crate_name: "loom",
-    srcs: ["tests/loom.rs"],
-    test_suites: ["general-tests"],
-    auto_gen_config: true,
     edition: "2018",
     features: [
         "alloc",
@@ -90,7 +60,6 @@ rust_defaults {
     ],
     rustlibs: [
         "libcfg_if",
-        "libcrossbeam_epoch",
         "libcrossbeam_utils",
         "liblazy_static",
         "libmemoffset",
@@ -99,23 +68,12 @@ rust_defaults {
     ],
 }
 
-rust_test_host {
-    name: "crossbeam-epoch_host_test_tests_loom",
-    defaults: ["crossbeam-epoch_defaults_loom"],
-    test_options: {
-        unit_test: true,
-    },
-}
-
-rust_test {
-    name: "crossbeam-epoch_device_test_tests_loom",
-    defaults: ["crossbeam-epoch_defaults_loom"],
-}
-
 rust_library {
     name: "libcrossbeam_epoch",
     host_supported: true,
     crate_name: "crossbeam_epoch",
+    cargo_env_compat: true,
+    cargo_pkg_version: "0.9.5",
     srcs: ["src/lib.rs"],
     edition: "2018",
     features: [
@@ -132,17 +90,3 @@ rust_library {
         "libscopeguard",
     ],
 }
-
-// dependent_library ["feature_list"]
-//   autocfg-1.0.1
-//   cfg-if-1.0.0
-//   crossbeam-utils-0.8.3 "lazy_static,std"
-//   getrandom-0.2.2 "std"
-//   lazy_static-1.4.0
-//   libc-0.2.92
-//   memoffset-0.6.3 "default"
-//   ppv-lite86-0.2.10 "simd,std"
-//   rand-0.8.3 "alloc,default,getrandom,libc,rand_chacha,rand_hc,std,std_rng"
-//   rand_chacha-0.3.0 "std"
-//   rand_core-0.6.2 "alloc,getrandom,std"
-//   scopeguard-1.1.0
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0f30b70..c78fbf8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,14 @@
+# Version 0.9.5
+
+- Fix UB in `Pointable` impl of `[MaybeUninit<T>]` (#694)
+- Support targets that do not have atomic CAS on stable Rust (#698)
+- Fix breakage with nightly feature due to rust-lang/rust#84510 (#692)
+
+# Version 0.9.4
+
+- Fix UB in `<[MaybeUninit<T>] as Pointable>::init` when global allocator failed allocation (#690)
+- Bump `loom` dependency to version 0.5. (#686)
+
 # Version 0.9.3
 
 - Make `loom` dependency optional. (#666)
diff --git a/Cargo.lock b/Cargo.lock
index fd37e90..596c26d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -10,9 +10,9 @@ checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
 
 [[package]]
 name = "cc"
-version = "1.0.67"
+version = "1.0.68"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e3c69b077ad434294d3ce9f1f6143a2a4b89a8a2d54ef813d85003a4fd1137fd"
+checksum = "4a72c244c1ff497a746a7e1fb3d14bd08420ecda70c8f25c7112f2781652d787"
 
 [[package]]
 name = "cfg-if"
@@ -22,13 +22,13 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "const_fn"
-version = "0.4.5"
+version = "0.4.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "28b9d6de7f49e22cf97ad17fc4036ece69300032f45f78f30b4a4482cdc3f4a6"
+checksum = "f92cfa0fd5690b3cf8c1ef2cabbd9b7ef22fa53cf5e1f92b05103f6d5d1cf6e7"
 
 [[package]]
 name = "crossbeam-epoch"
-version = "0.9.3"
+version = "0.9.5"
 dependencies = [
  "cfg-if",
  "const_fn",
@@ -42,11 +42,10 @@ dependencies = [
 
 [[package]]
 name = "crossbeam-utils"
-version = "0.8.3"
+version = "0.8.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e7e9d99fa91428effe99c5c6d4634cdeba32b8cf784fc428a2a687f61a952c49"
+checksum = "d82cfc11ce7f2c3faef78d8a684447b40d503d9681acebed6cb728d45940c4db"
 dependencies = [
- "autocfg",
  "cfg-if",
  "lazy_static",
  "loom",
@@ -54,9 +53,9 @@ dependencies = [
 
 [[package]]
 name = "generator"
-version = "0.6.24"
+version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a9fed24fd1e18827652b4d55652899a1e9da8e54d91624dc3437a5bc3a9f9a9c"
+checksum = "c1d9279ca822891c1a4dae06d185612cf8fc6acfe5dff37781b41297811b12ee"
 dependencies = [
  "cc",
  "libc",
@@ -67,9 +66,9 @@ dependencies = [
 
 [[package]]
 name = "getrandom"
-version = "0.2.2"
+version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8"
+checksum = "7fcd999463524c52659517fe2cea98493cfe485d10565e7b0fb07dbba7ad2753"
 dependencies = [
  "cfg-if",
  "libc",
@@ -84,9 +83,9 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.86"
+version = "0.2.95"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c"
+checksum = "789da6d93f1b866ffe175afc5322a4d76c038605a1c3319bb57b06967ca98a36"
 
 [[package]]
 name = "log"
@@ -99,9 +98,9 @@ dependencies = [
 
 [[package]]
 name = "loom"
-version = "0.4.0"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d44c73b4636e497b4917eb21c33539efa3816741a2d3ff26c6316f1b529481a4"
+checksum = "7aa5348dc45fa5f2419b6dd4ea20345e6b01b1fcc9d176a322eada1ac3f382ba"
 dependencies = [
  "cfg-if",
  "generator",
@@ -110,9 +109,9 @@ dependencies = [
 
 [[package]]
 name = "memoffset"
-version = "0.6.1"
+version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "157b4208e3059a8f9e78d559edc658e13df41410cb3ae03979c83130067fdd87"
+checksum = "59accc507f1338036a0477ef61afdae33cde60840f4dfe481319ce3ad116ddf9"
 dependencies = [
  "autocfg",
 ]
@@ -165,9 +164,9 @@ dependencies = [
 
 [[package]]
 name = "rustversion"
-version = "1.0.4"
+version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cb5d2a036dc6d2d8fd16fde3498b04306e29bd193bf306a57427019b823d5acd"
+checksum = "61b3909d758bb75c79f23d4736fac9433868679d3ad2ea7a61e3c25cfda9a088"
 
 [[package]]
 name = "scoped-tls"
diff --git a/Cargo.toml b/Cargo.toml
index 2d7eb00..97f3df3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,7 @@
 [package]
 edition = "2018"
 name = "crossbeam-epoch"
-version = "0.9.3"
+version = "0.9.5"
 authors = ["The Crossbeam Project Developers"]
 description = "Epoch-based garbage collection"
 homepage = "https://github.com/crossbeam-rs/crossbeam/tree/master/crossbeam-epoch"
@@ -30,7 +30,7 @@ version = "0.4.4"
 optional = true
 
 [dependencies.crossbeam-utils]
-version = "0.8.3"
+version = "0.8.5"
 default-features = false
 
 [dependencies.lazy_static]
@@ -53,6 +53,6 @@ loom = ["loom-crate", "crossbeam-utils/loom"]
 nightly = ["crossbeam-utils/nightly", "const_fn"]
 std = ["alloc", "crossbeam-utils/std", "lazy_static"]
 [target."cfg(crossbeam_loom)".dependencies.loom-crate]
-version = "0.4"
+version = "0.5"
 optional = true
 package = "loom"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
index 8961f25..939e346 100644
--- a/Cargo.toml.orig
+++ b/Cargo.toml.orig
@@ -4,7 +4,7 @@ name = "crossbeam-epoch"
 # - Update CHANGELOG.md
 # - Update README.md
 # - Create "crossbeam-epoch-X.Y.Z" git tag
-version = "0.9.3"
+version = "0.9.5"
 authors = ["The Crossbeam Project Developers"]
 edition = "2018"
 license = "MIT OR Apache-2.0"
@@ -24,18 +24,21 @@ std = ["alloc", "crossbeam-utils/std", "lazy_static"]
 
 # Enable to use APIs that require `alloc`.
 # This is enabled by default and also enabled if the `std` feature is enabled.
+#
+# NOTE: Disabling both `std` *and* `alloc` features is not supported yet.
 alloc = []
 
 # Enable to use of unstable functionality.
 # This is disabled by default and requires recent nightly compiler.
-# Note that this is outside of the normal semver guarantees and minor versions
-# of crossbeam may make breaking changes to them at any time.
+#
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
 nightly = ["crossbeam-utils/nightly", "const_fn"]
 
 # Enable the use of loom for concurrency testing.
 #
-# This configuration option is outside of the normal semver guarantees: minor
-# versions of crossbeam may make breaking changes to it at any time.
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
 loom = ["loom-crate", "crossbeam-utils/loom"]
 
 [dependencies]
@@ -45,13 +48,13 @@ memoffset = "0.6"
 
 # Enable the use of loom for concurrency testing.
 #
-# This configuration option is outside of the normal semver guarantees: minor
-# versions of crossbeam may make breaking changes to it at any time.
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
 [target.'cfg(crossbeam_loom)'.dependencies]
-loom-crate = { package = "loom", version = "0.4", optional = true }
+loom-crate = { package = "loom", version = "0.5", optional = true }
 
 [dependencies.crossbeam-utils]
-version = "0.8.3"
+version = "0.8.5"
 path = "../crossbeam-utils"
 default-features = false
 
diff --git a/METADATA b/METADATA
index fc37c40..626ee8f 100644
--- a/METADATA
+++ b/METADATA
@@ -7,13 +7,13 @@ third_party {
   }
   url {
     type: ARCHIVE
-    value: "https://static.crates.io/crates/crossbeam-epoch/crossbeam-epoch-0.9.3.crate"
+    value: "https://static.crates.io/crates/crossbeam-epoch/crossbeam-epoch-0.9.5.crate"
   }
-  version: "0.9.3"
+  version: "0.9.5"
   license_type: NOTICE
   last_upgrade_date {
     year: 2021
-    month: 4
-    day: 1
+    month: 6
+    day: 21
   }
 }
diff --git a/README.md b/README.md
index c8ebd87..eb33bad 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ https://crates.io/crates/crossbeam-epoch)
 https://docs.rs/crossbeam-epoch)
 [![Rust 1.36+](https://img.shields.io/badge/rust-1.36+-lightgray.svg)](
 https://www.rust-lang.org)
-[![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.gg/BBYwKq)
+[![chat](https://img.shields.io/discord/569610676205781012.svg?logo=discord)](https://discord.com/invite/JXYwgWZ)
 
 This crate provides epoch-based garbage collection for building concurrent data structures.
 
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 25a9cdc..161921c 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -1,8 +1,30 @@
 // Generated by update_crate_tests.py for tests that depend on this crate.
 {
+  "imports": [
+    {
+      "path": "external/rust/crates/base64"
+    },
+    {
+      "path": "external/rust/crates/crossbeam-deque"
+    },
+    {
+      "path": "external/rust/crates/tinytemplate"
+    },
+    {
+      "path": "external/rust/crates/tinyvec"
+    },
+    {
+      "path": "external/rust/crates/unicode-xid"
+    }
+  ],
   "presubmit": [
     {
-      "name": "crossbeam-epoch_device_test_src_lib"
+      "name": "crossbeam-epoch_test_src_lib"
+    }
+  ],
+  "presubmit-rust": [
+    {
+      "name": "crossbeam-epoch_test_src_lib"
     }
   ]
 }
diff --git a/build.rs b/build.rs
new file mode 100644
index 0000000..4ef1279
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,32 @@
+#![warn(rust_2018_idioms)]
+
+use std::env;
+
+include!("no_atomic.rs");
+
+// The rustc-cfg strings below are *not* public API. Please let us know by
+// opening a GitHub issue if your build environment requires some way to enable
+// these cfgs other than by executing our build script.
+fn main() {
+    let target = match env::var("TARGET") {
+        Ok(target) => target,
+        Err(e) => {
+            println!(
+                "cargo:warning={}: unable to get TARGET environment variable: {}",
+                env!("CARGO_PKG_NAME"),
+                e
+            );
+            return;
+        }
+    };
+
+    // Note that this is `no_*`, not `has_*`. This allows treating
+    // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+    // run. This is needed for compatibility with non-cargo build systems that
+    // don't run the build script.
+    if NO_ATOMIC_CAS.contains(&&*target) {
+        println!("cargo:rustc-cfg=crossbeam_no_atomic_cas");
+    }
+
+    println!("cargo:rerun-if-changed=no_atomic.rs");
+}
diff --git a/cargo2android.json b/cargo2android.json
new file mode 100644
index 0000000..d36fb44
--- /dev/null
+++ b/cargo2android.json
@@ -0,0 +1,5 @@
+{
+  "device": true,
+  "run": true,
+  "tests": true
+}
\ No newline at end of file
diff --git a/no_atomic.rs b/no_atomic.rs
new file mode 100644
index 0000000..522b3b8
--- /dev/null
+++ b/no_atomic.rs
@@ -0,0 +1,59 @@
+// This file is @generated by no_atomic.sh.
+// It is not intended for manual editing.
+
+const NO_ATOMIC_CAS: &[&str] = &[
+    "avr-unknown-gnu-atmega328",
+    "msp430-none-elf",
+    "riscv32i-unknown-none-elf",
+    "riscv32imc-unknown-none-elf",
+    "thumbv4t-none-eabi",
+    "thumbv6m-none-eabi",
+];
+#[allow(dead_code)]
+const NO_ATOMIC_64: &[&str] = &[
+    "arm-linux-androideabi",
+    "armebv7r-none-eabi",
+    "armebv7r-none-eabihf",
+    "armv4t-unknown-linux-gnueabi",
+    "armv5te-unknown-linux-gnueabi",
+    "armv5te-unknown-linux-musleabi",
+    "armv5te-unknown-linux-uclibceabi",
+    "armv7r-none-eabi",
+    "armv7r-none-eabihf",
+    "hexagon-unknown-linux-musl",
+    "mips-unknown-linux-gnu",
+    "mips-unknown-linux-musl",
+    "mips-unknown-linux-uclibc",
+    "mipsel-unknown-linux-gnu",
+    "mipsel-unknown-linux-musl",
+    "mipsel-unknown-linux-uclibc",
+    "mipsel-unknown-none",
+    "mipsisa32r6-unknown-linux-gnu",
+    "mipsisa32r6el-unknown-linux-gnu",
+    "powerpc-unknown-linux-gnu",
+    "powerpc-unknown-linux-gnuspe",
+    "powerpc-unknown-linux-musl",
+    "powerpc-unknown-netbsd",
+    "powerpc-unknown-openbsd",
+    "powerpc-wrs-vxworks",
+    "powerpc-wrs-vxworks-spe",
+    "riscv32gc-unknown-linux-gnu",
+    "riscv32gc-unknown-linux-musl",
+    "riscv32imac-unknown-none-elf",
+    "thumbv7em-none-eabi",
+    "thumbv7em-none-eabihf",
+    "thumbv7m-none-eabi",
+    "thumbv8m.base-none-eabi",
+    "thumbv8m.main-none-eabi",
+    "thumbv8m.main-none-eabihf",
+    "mipsel-sony-psp",
+    "thumbv4t-none-eabi",
+    "thumbv6m-none-eabi",
+];
+#[allow(dead_code)]
+const NO_ATOMIC: &[&str] = &[
+    "avr-unknown-gnu-atmega328",
+    "msp430-none-elf",
+    "riscv32i-unknown-none-elf",
+    "riscv32imc-unknown-none-elf",
+];
diff --git a/src/atomic.rs b/src/atomic.rs
index e4ca23f..adb0afa 100644
--- a/src/atomic.rs
+++ b/src/atomic.rs
@@ -238,7 +238,8 @@ impl<T> Pointable for T {
 // [`alloc::alloc::Layout::extend`] instead.
 #[repr(C)]
 struct Array<T> {
-    size: usize,
+    /// The number of elements (not the number of bytes).
+    len: usize,
     elements: [MaybeUninit<T>; 0],
 }
 
@@ -247,28 +248,31 @@ impl<T> Pointable for [MaybeUninit<T>] {
 
     type Init = usize;
 
-    unsafe fn init(size: Self::Init) -> usize {
-        let size = mem::size_of::<Array<T>>() + mem::size_of::<MaybeUninit<T>>() * size;
+    unsafe fn init(len: Self::Init) -> usize {
+        let size = mem::size_of::<Array<T>>() + mem::size_of::<MaybeUninit<T>>() * len;
         let align = mem::align_of::<Array<T>>();
         let layout = alloc::Layout::from_size_align(size, align).unwrap();
         let ptr = alloc::alloc(layout) as *mut Array<T>;
-        (*ptr).size = size;
+        if ptr.is_null() {
+            alloc::handle_alloc_error(layout);
+        }
+        (*ptr).len = len;
         ptr as usize
     }
 
     unsafe fn deref<'a>(ptr: usize) -> &'a Self {
         let array = &*(ptr as *const Array<T>);
-        slice::from_raw_parts(array.elements.as_ptr() as *const _, array.size)
+        slice::from_raw_parts(array.elements.as_ptr() as *const _, array.len)
     }
 
     unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut Self {
         let array = &*(ptr as *mut Array<T>);
-        slice::from_raw_parts_mut(array.elements.as_ptr() as *mut _, array.size)
+        slice::from_raw_parts_mut(array.elements.as_ptr() as *mut _, array.len)
     }
 
     unsafe fn drop(ptr: usize) {
         let array = &*(ptr as *mut Array<T>);
-        let size = mem::size_of::<Array<T>>() + mem::size_of::<MaybeUninit<T>>() * array.size;
+        let size = mem::size_of::<Array<T>>() + mem::size_of::<MaybeUninit<T>>() * array.len;
         let align = mem::align_of::<Array<T>>();
         let layout = alloc::Layout::from_size_align(size, align).unwrap();
         alloc::dealloc(ptr as *mut u8, layout);
@@ -1526,7 +1530,8 @@ impl<T: ?Sized + Pointable> Default for Shared<'_, T> {
 
 #[cfg(all(test, not(crossbeam_loom)))]
 mod tests {
-    use super::Shared;
+    use super::{Owned, Shared};
+    use std::mem::MaybeUninit;
 
     #[test]
     fn valid_tag_i8() {
@@ -1542,6 +1547,13 @@ mod tests {
     #[test]
     fn const_atomic_null() {
         use super::Atomic;
-        const _: Atomic<u8> = Atomic::<u8>::null();
+        static _U: Atomic<u8> = Atomic::<u8>::null();
+    }
+
+    #[test]
+    fn array_init() {
+        let owned = Owned::<[MaybeUninit<usize>]>::init(10);
+        let arr: &[MaybeUninit<usize>] = &*owned;
+        assert_eq!(arr.len(), 10);
     }
 }
diff --git a/src/lib.rs b/src/lib.rs
index 99da911..ba1d331 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -62,8 +62,7 @@
     unreachable_pub
 )]
 #![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(feature = "nightly", feature(cfg_target_has_atomic))]
-#![cfg_attr(feature = "nightly", feature(const_fn))]
+#![cfg_attr(feature = "nightly", feature(const_fn_trait_bound))]
 
 #[cfg(crossbeam_loom)]
 extern crate loom_crate as loom;
@@ -105,10 +104,11 @@ mod primitive {
     pub(crate) use loom::lazy_static;
     pub(crate) use loom::thread_local;
 }
+#[cfg(not(crossbeam_no_atomic_cas))]
 #[cfg(not(crossbeam_loom))]
 #[allow(unused_imports, dead_code)]
 mod primitive {
-    #[cfg(any(feature = "alloc", feature = "std"))]
+    #[cfg(feature = "alloc")]
     pub(crate) mod cell {
         #[derive(Debug)]
         #[repr(transparent)]
@@ -136,14 +136,13 @@ mod primitive {
             }
         }
     }
-    #[cfg(any(feature = "alloc", feature = "std"))]
+    #[cfg(feature = "alloc")]
     pub(crate) mod sync {
         pub(crate) mod atomic {
             pub(crate) use core::sync::atomic::compiler_fence;
             pub(crate) use core::sync::atomic::fence;
             pub(crate) use core::sync::atomic::AtomicUsize;
         }
-        #[cfg_attr(feature = "nightly", cfg(target_has_atomic = "ptr"))]
         pub(crate) use alloc::sync::Arc;
     }
 
@@ -154,7 +153,7 @@ mod primitive {
     pub(crate) use lazy_static::lazy_static;
 }
 
-#[cfg_attr(feature = "nightly", cfg(target_has_atomic = "ptr"))]
+#[cfg(not(crossbeam_no_atomic_cas))]
 cfg_if! {
     if #[cfg(feature = "alloc")] {
         extern crate alloc;