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-rw-r--r--.cargo_vcs_info.json2
-rw-r--r--.github/workflows/ci.yaml5
-rw-r--r--Android.bp38
-rw-r--r--CHANGELOG.md59
-rw-r--r--Cargo.toml52
-rw-r--r--Cargo.toml.orig43
-rw-r--r--METADATA14
-rw-r--r--README.md4
-rw-r--r--TEST_MAPPING74
-rw-r--r--cargo2android.json12
-rw-r--r--examples/lazy_static.rs2
-rw-r--r--patches/Android.bp.patch47
-rw-r--r--patches/imp_std.rs.patch6
-rw-r--r--patches/it.rs.patch20
-rw-r--r--src/imp_cs.rs78
-rw-r--r--src/imp_pl.rs105
-rw-r--r--src/imp_std.rs279
-rw-r--r--src/lib.rs273
-rw-r--r--src/race.rs135
-rw-r--r--tests/it.rs130
20 files changed, 1073 insertions, 305 deletions
diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
index f070bea..8f875ed 100644
--- a/.cargo_vcs_info.json
+++ b/.cargo_vcs_info.json
@@ -1,6 +1,6 @@
{
"git": {
- "sha1": "44852cc72dbfbf57c5477a907ec0ab36527bc36b"
+ "sha1": "35148638c54c6233545c65d1a5e09d5ba0661806"
},
"path_in_vcs": ""
} \ No newline at end of file
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 7967bb9..6a998a8 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -21,7 +21,8 @@ jobs:
- uses: actions/checkout@v2
with:
fetch-depth: 0 # fetch tags for publish
-
+ - uses: Swatinem/rust-cache@359a70e43a0bb8a13953b04a90f76428b4959bb6
- run: cargo run -p xtask -- ci
env:
- CRATES_IO_TOKEN: ${{ secrets.CRATES_IO_TOKEN }}
+ CARGO_REGISTRY_TOKEN: ${{ secrets.CRATES_IO_TOKEN }}
+ MIRIFLAGS: -Zmiri-strict-provenance
diff --git a/Android.bp b/Android.bp
index 7211fe6..e9b9198 100644
--- a/Android.bp
+++ b/Android.bp
@@ -42,9 +42,9 @@ rust_library {
host_supported: true,
crate_name: "once_cell",
cargo_env_compat: true,
- cargo_pkg_version: "1.9.0",
+ cargo_pkg_version: "1.17.1",
srcs: ["src/lib.rs"],
- edition: "2018",
+ edition: "2021",
features: [
"alloc",
"default",
@@ -53,10 +53,30 @@ rust_library {
],
apex_available: [
"//apex_available:platform",
- "com.android.compos",
- "com.android.resolv",
- "com.android.virt",
+ "//apex_available:anyapex",
],
+ product_available: true,
+ vendor_available: true,
+ min_sdk_version: "29",
+}
+
+rust_library_rlib {
+ name: "libonce_cell_nostd",
+ crate_name: "once_cell",
+ cargo_env_compat: true,
+ cargo_pkg_version: "1.16.0",
+ srcs: ["src/lib.rs"],
+ edition: "2021",
+ features: [
+ "alloc",
+ "default",
+ "race",
+ ],
+ apex_available: [
+ "//apex_available:platform",
+ "//apex_available:anyapex"
+ ],
+ vendor_available: true,
min_sdk_version: "29",
}
@@ -65,14 +85,14 @@ rust_test {
host_supported: true,
crate_name: "once_cell",
cargo_env_compat: true,
- cargo_pkg_version: "1.9.0",
+ cargo_pkg_version: "1.17.1",
srcs: ["src/lib.rs"],
test_suites: ["general-tests"],
auto_gen_config: true,
test_options: {
unit_test: true,
},
- edition: "2018",
+ edition: "2021",
features: [
"alloc",
"default",
@@ -91,14 +111,14 @@ rust_test {
host_supported: true,
crate_name: "it",
cargo_env_compat: true,
- cargo_pkg_version: "1.9.0",
+ cargo_pkg_version: "1.17.1",
srcs: ["tests/it.rs"],
test_suites: ["general-tests"],
auto_gen_config: true,
test_options: {
unit_test: true,
},
- edition: "2018",
+ edition: "2021",
features: [
"alloc",
"default",
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2c95053..bf489b2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,63 @@
# Changelog
-## 1.9
+## Unreleased
+
+-
+
+## 1.17.1
+
+- Make `OnceRef` implementation compliant with [strict provenance](https://github.com/rust-lang/rust/issues/95228).
+
+## 1.17.0
+
+- Add `race::OnceRef` for storing a `&'a T`.
+
+## 1.16.0
+
+- Add `no_std` implementation based on `critical-section`,
+ [#195](https://github.com/matklad/once_cell/pull/195).
+- Deprecate `atomic-polyfill` feature (use the new `critical-section` instead)
+
+## 1.15.0
+
+- Increase minimal supported Rust version to 1.56.0.
+- Implement `UnwindSafe` even if the `std` feature is disabled.
+
+## 1.14.0
+
+- Add extension to `unsync` and `sync` `Lazy` mut API:
+ - `force_mut`
+ - `get_mut`
+
+
+## 1.13.1
+
+- Make implementation compliant with [strict provenance](https://github.com/rust-lang/rust/issues/95228).
+- Upgrade `atomic-polyfill` to `1.0`
+
+## 1.13.0
+
+- Add `Lazy::get`, similar to `OnceCell::get`.
+
+## 1.12.1
+
+- Remove incorrect `debug_assert`.
+
+## 1.12.0
+
+- Add `OnceCell::wait`, a blocking variant of `get`.
+
+## 1.11.0
+
+- Add `OnceCell::with_value` to create initialized `OnceCell` in `const` context.
+- Improve `Clone` implementation for `OnceCell`.
+- Rewrite `parking_lot` version on top of `parking_lot_core`, for even smaller cells!
+
+## 1.10.0
+
+- upgrade `parking_lot` to `0.12.0` (note that this bumps MSRV with `parking_lot` feature enabled to `1.49.0`).
+
+## 1.9.0
- Added an `atomic-polyfill` optional dependency to compile `race` on platforms without atomics
diff --git a/Cargo.toml b/Cargo.toml
index 0a94bfc..76a6291 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,18 +10,31 @@
# See Cargo.toml.orig for the original contents.
[package]
-edition = "2018"
+edition = "2021"
+rust-version = "1.56"
name = "once_cell"
-version = "1.9.0"
+version = "1.17.1"
authors = ["Aleksey Kladov <aleksey.kladov@gmail.com>"]
-exclude = ["*.png", "*.svg", "/Cargo.lock.msrv", "/.travis.yml", "/run-miri-tests.sh", "rustfmt.toml"]
+exclude = [
+ "*.png",
+ "*.svg",
+ "/Cargo.lock.msrv",
+ "rustfmt.toml",
+]
description = "Single assignment cells and lazy values."
documentation = "https://docs.rs/once_cell"
readme = "README.md"
-keywords = ["lazy", "static"]
-categories = ["rust-patterns", "memory-management"]
+keywords = [
+ "lazy",
+ "static",
+]
+categories = [
+ "rust-patterns",
+ "memory-management",
+]
license = "MIT OR Apache-2.0"
repository = "https://github.com/matklad/once_cell"
+
[package.metadata.docs.rs]
all-features = true
@@ -52,16 +65,29 @@ required-features = ["std"]
[[example]]
name = "test_synchronization"
required-features = ["std"]
-[dependencies.atomic-polyfill]
-version = "0.1"
+
+[dependencies.atomic_polyfill]
+version = "1"
+optional = true
+package = "atomic-polyfill"
+
+[dependencies.critical_section]
+version = "1"
optional = true
+package = "critical-section"
-[dependencies.parking_lot]
-version = "0.11"
+[dependencies.parking_lot_core]
+version = "0.9.3"
optional = true
default_features = false
+
+[dev-dependencies.critical_section]
+version = "1.1.1"
+features = ["std"]
+package = "critical-section"
+
[dev-dependencies.crossbeam-utils]
-version = "0.7.2"
+version = "0.8.7"
[dev-dependencies.lazy_static]
version = "1.0.0"
@@ -71,7 +97,13 @@ version = "1.2.0"
[features]
alloc = ["race"]
+atomic-polyfill = ["critical-section"]
+critical-section = [
+ "critical_section",
+ "atomic_polyfill",
+]
default = ["std"]
+parking_lot = ["parking_lot_core"]
race = []
std = ["alloc"]
unstable = []
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
index 3b2d1aa..ad02c34 100644
--- a/Cargo.toml.orig
+++ b/Cargo.toml.orig
@@ -1,9 +1,10 @@
[package]
name = "once_cell"
-version = "1.9.0"
+version = "1.17.1"
authors = ["Aleksey Kladov <aleksey.kladov@gmail.com>"]
license = "MIT OR Apache-2.0"
-edition = "2018"
+edition = "2021"
+rust-version = "1.56"
description = "Single assignment cells and lazy values."
readme = "README.md"
@@ -13,41 +14,53 @@ repository = "https://github.com/matklad/once_cell"
keywords = ["lazy", "static"]
categories = ["rust-patterns", "memory-management"]
-exclude = ["*.png", "*.svg", "/Cargo.lock.msrv", "/.travis.yml", "/run-miri-tests.sh", "rustfmt.toml"]
+exclude = ["*.png", "*.svg", "/Cargo.lock.msrv", "rustfmt.toml"]
[workspace]
members = ["xtask"]
[dependencies]
-# Uses parking_lot to implement once_cell::sync::OnceCell.
-# This makes not speed difference, but makes each OnceCell<T>
-# for up to 16 bytes smaller, depending on the size of the T.
-parking_lot = { version = "0.11", optional = true, default_features = false }
-
-# To be used in order to enable the race feature on targets
-# that do not have atomics
-# *Warning:* This can be unsound. Please read the README of
-# [atomic-polyfill](https://github.com/embassy-rs/atomic-polyfill)
-# and make sure you understand all the implications
-atomic-polyfill = { version = "0.1", optional = true }
+# These optional dependencies are considered private impl details,
+# only features from `[features]` table are a part of semver-guarded API.
+parking_lot_core = { version = "0.9.3", optional = true, default_features = false }
+atomic_polyfill = { package = "atomic-polyfill", version = "1", optional = true }
+critical_section = { package = "critical-section", version = "1", optional = true }
[dev-dependencies]
lazy_static = "1.0.0"
-crossbeam-utils = "0.7.2"
+crossbeam-utils = "0.8.7"
regex = "1.2.0"
+critical_section = { package = "critical-section", version = "1.1.1", features = ["std"] }
[features]
default = ["std"]
+
# Enables `once_cell::sync` module.
std = ["alloc"]
+
# Enables `once_cell::race::OnceBox` type.
alloc = ["race"]
+
# Enables `once_cell::race` module.
race = []
+
+# Uses parking_lot to implement once_cell::sync::OnceCell.
+# This makes no speed difference, but makes each OnceCell<T>
+# up to 16 bytes smaller, depending on the size of the T.
+parking_lot = ["parking_lot_core"]
+
+# Uses `critical-section` to implement `sync` and `race` modules. in
+# `#![no_std]` mode. Please read `critical-section` docs carefully
+# before enabling this feature.
+critical-section = ["critical_section", "atomic_polyfill" ]
+
# Enables semver-exempt APIs of this crate.
# At the moment, this feature is unused.
unstable = []
+# Only for backwards compatibility.
+atomic-polyfill = ["critical-section"]
+
[[example]]
name = "bench"
required-features = ["std"]
diff --git a/METADATA b/METADATA
index 4b16d85..79a823c 100644
--- a/METADATA
+++ b/METADATA
@@ -1,3 +1,7 @@
+# This project was upgraded with external_updater.
+# Usage: tools/external_updater/updater.sh update rust/crates/once_cell
+# For more info, check https://cs.android.com/android/platform/superproject/+/master:tools/external_updater/README.md
+
name: "once_cell"
description: "Single assignment cells and lazy values."
third_party {
@@ -7,13 +11,13 @@ third_party {
}
url {
type: ARCHIVE
- value: "https://static.crates.io/crates/once_cell/once_cell-1.9.0.crate"
+ value: "https://static.crates.io/crates/once_cell/once_cell-1.17.1.crate"
}
- version: "1.9.0"
+ version: "1.17.1"
license_type: NOTICE
last_upgrade_date {
- year: 2022
- month: 3
- day: 1
+ year: 2023
+ month: 2
+ day: 16
}
}
diff --git a/README.md b/README.md
index b5c9896..737f2de 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
<p align="center"><img src="design/logo.png" alt="once_cell"></p>
-[![Build Status](https://travis-ci.org/matklad/once_cell.svg?branch=master)](https://travis-ci.org/matklad/once_cell)
+[![Build Status](https://github.com/matklad/once_cell/actions/workflows/ci.yaml/badge.svg)](https://github.com/matklad/once_cell/actions)
[![Crates.io](https://img.shields.io/crates/v/once_cell.svg)](https://crates.io/crates/once_cell)
[![API reference](https://docs.rs/once_cell/badge.svg)](https://docs.rs/once_cell/)
@@ -51,6 +51,8 @@ More patterns and use-cases are in the [docs](https://docs.rs/once_cell/)!
* [lazycell](https://crates.io/crates/lazycell)
* [mitochondria](https://crates.io/crates/mitochondria)
* [lazy_static](https://crates.io/crates/lazy_static)
+* [async_once_cell](https://crates.io/crates/async_once_cell)
+* [generic_once_cell](https://crates.io/crates/generic_once_cell) (bring your own mutex)
The API of `once_cell` is being proposed for inclusion in
[`std`](https://github.com/rust-lang/rfcs/pull/2788).
diff --git a/TEST_MAPPING b/TEST_MAPPING
index febfdce..153b0f1 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -2,98 +2,104 @@
{
"imports": [
{
- "path": "external/rust/crates/quiche"
+ "path": "external/rust/crates/android_logger"
},
{
- "path": "external/rust/crates/ring"
+ "path": "external/rust/crates/argh"
},
{
- "path": "external/rust/crates/thread_local"
+ "path": "external/rust/crates/base64"
},
{
- "path": "external/rust/crates/webpki"
- }
- ],
- "presubmit": [
+ "path": "external/rust/crates/hashbrown"
+ },
{
- "name": "ZipFuseTest"
+ "path": "external/rust/crates/hashlink"
},
{
- "name": "apkdmverity.test"
+ "path": "external/rust/crates/libsqlite3-sys"
},
{
- "name": "authfs_device_test_src_lib"
+ "path": "external/rust/crates/quiche"
},
{
- "name": "doh_unit_test"
+ "path": "external/rust/crates/ring"
},
{
- "name": "keystore2_test"
+ "path": "external/rust/crates/thread_local"
},
{
- "name": "legacykeystore_test"
+ "path": "external/rust/crates/tinytemplate"
},
{
- "name": "libapkverify.integration_test"
+ "path": "external/rust/crates/tinyvec"
},
{
- "name": "libapkverify.test"
+ "path": "external/rust/crates/unicode-xid"
},
{
- "name": "libidsig.test"
+ "path": "external/rust/crates/webpki"
},
{
- "name": "microdroid_manager_test"
+ "path": "packages/modules/DnsResolver"
},
{
- "name": "once_cell_test_src_lib"
+ "path": "packages/modules/Virtualization/apkdmverity"
},
{
- "name": "once_cell_test_tests_it"
+ "path": "packages/modules/Virtualization/authfs"
},
{
- "name": "virtualizationservice_device_test"
- }
- ],
- "presubmit-rust": [
+ "path": "packages/modules/Virtualization/avmd"
+ },
{
- "name": "ZipFuseTest"
+ "path": "packages/modules/Virtualization/encryptedstore"
},
{
- "name": "apkdmverity.test"
+ "path": "packages/modules/Virtualization/libs/apkverify"
},
{
- "name": "authfs_device_test_src_lib"
+ "path": "packages/modules/Virtualization/microdroid_manager"
},
{
- "name": "doh_unit_test"
+ "path": "packages/modules/Virtualization/virtualizationmanager"
},
{
- "name": "keystore2_test"
+ "path": "packages/modules/Virtualization/vm"
},
{
- "name": "legacykeystore_test"
+ "path": "packages/modules/Virtualization/zipfuse"
},
{
- "name": "libapkverify.integration_test"
+ "path": "system/logging/rust"
},
{
- "name": "libapkverify.test"
+ "path": "system/security/diced"
},
{
- "name": "libidsig.test"
+ "path": "system/security/keystore2"
},
{
- "name": "microdroid_manager_test"
+ "path": "system/security/keystore2/legacykeystore"
},
{
+ "path": "system/security/keystore2/selinux"
+ }
+ ],
+ "presubmit": [
+ {
"name": "once_cell_test_src_lib"
},
{
"name": "once_cell_test_tests_it"
+ }
+ ],
+ "presubmit-rust": [
+ {
+ "name": "once_cell_test_src_lib"
},
{
- "name": "virtualizationservice_device_test"
+ "name": "once_cell_test_tests_it"
}
]
}
diff --git a/cargo2android.json b/cargo2android.json
index 506d866..674f610 100644
--- a/cargo2android.json
+++ b/cargo2android.json
@@ -1,13 +1,9 @@
{
- "apex-available": [
- "//apex_available:platform",
- "com.android.compos",
- "com.android.resolv",
- "com.android.virt"
- ],
"dependencies": true,
"device": true,
"min-sdk-version": "29",
+ "patch": "patches/Android.bp.patch",
"run": true,
- "tests": true
-} \ No newline at end of file
+ "tests": true,
+ "vendor-available": true
+}
diff --git a/examples/lazy_static.rs b/examples/lazy_static.rs
index f050560..3cdb19f 100644
--- a/examples/lazy_static.rs
+++ b/examples/lazy_static.rs
@@ -32,5 +32,5 @@ fn main() {
// The same works for function-style:
assert_eq!(hashmap().get(&0), Some(&"foo"));
- assert_eq!(hashmap().get(&0), Some(&"bar"));
+ assert_eq!(hashmap().get(&1), Some(&"bar"));
}
diff --git a/patches/Android.bp.patch b/patches/Android.bp.patch
new file mode 100644
index 0000000..6dee374
--- /dev/null
+++ b/patches/Android.bp.patch
@@ -0,0 +1,47 @@
+diff --git a/Android.bp b/Android.bp
+index d6878ec..59ae682 100644
+--- a/Android.bp
++++ b/Android.bp
+@@ -59,6 +59,26 @@ rust_library {
+ min_sdk_version: "29",
+ }
+
++rust_library_rlib {
++ name: "libonce_cell_nostd",
++ crate_name: "once_cell",
++ cargo_env_compat: true,
++ cargo_pkg_version: "1.16.0",
++ srcs: ["src/lib.rs"],
++ edition: "2021",
++ features: [
++ "alloc",
++ "default",
++ "race",
++ ],
++ apex_available: [
++ "//apex_available:platform",
++ "//apex_available:anyapex"
++ ],
++ vendor_available: true,
++ min_sdk_version: "29",
++}
++
+ rust_test {
+ name: "once_cell_test_src_lib",
+ host_supported: true,
+@@ -79,7 +99,6 @@ rust_test {
+ "std",
+ ],
+ rustlibs: [
+- "libcritical_section",
+ "libcrossbeam_utils",
+ "liblazy_static",
+ "libregex",
+@@ -106,7 +125,6 @@ rust_test {
+ "std",
+ ],
+ rustlibs: [
+- "libcritical_section",
+ "libcrossbeam_utils",
+ "liblazy_static",
+ "libonce_cell",
diff --git a/patches/imp_std.rs.patch b/patches/imp_std.rs.patch
index 556297f..4916e3a 100644
--- a/patches/imp_std.rs.patch
+++ b/patches/imp_std.rs.patch
@@ -1,8 +1,8 @@
diff --git a/src/imp_std.rs b/src/imp_std.rs
-index d7dda96..f461c3d 100644
+index 5761f01..d727851 100644
--- a/src/imp_std.rs
+++ b/src/imp_std.rs
-@@ -299,6 +299,7 @@ mod tests {
+@@ -358,6 +358,7 @@ mod tests {
}
#[test]
@@ -10,7 +10,7 @@ index d7dda96..f461c3d 100644
fn poison_bad() {
static O: OnceCell<()> = OnceCell::new();
-@@ -320,6 +321,7 @@ mod tests {
+@@ -379,6 +380,7 @@ mod tests {
}
#[test]
diff --git a/patches/it.rs.patch b/patches/it.rs.patch
index 8491db5..4d1d23f 100644
--- a/patches/it.rs.patch
+++ b/patches/it.rs.patch
@@ -1,8 +1,8 @@
diff --git a/tests/it.rs b/tests/it.rs
-index 81faaff..c769487 100644
+index d18f0a1..f94bc69 100644
--- a/tests/it.rs
+++ b/tests/it.rs
-@@ -166,6 +166,7 @@ mod unsync {
+@@ -208,6 +208,7 @@ mod unsync {
#[test]
#[cfg(feature = "std")]
@@ -10,7 +10,15 @@ index 81faaff..c769487 100644
fn lazy_poisoning() {
let x: Lazy<String> = Lazy::new(|| panic!("kaboom"));
for _ in 0..2 {
-@@ -288,6 +289,7 @@ mod sync {
+@@ -227,6 +228,7 @@ mod unsync {
+
+ #[test]
+ #[should_panic(expected = "reentrant init")]
++ #[ignore = "Android: ignore for now. Need to compile these binaries separately."]
+ fn reentrant_init() {
+ let x: OnceCell<Box<i32>> = OnceCell::new();
+ let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
+@@ -342,6 +344,7 @@ mod sync {
}
#[test]
@@ -18,15 +26,15 @@ index 81faaff..c769487 100644
fn get_or_try_init() {
let cell: OnceCell<String> = OnceCell::new();
assert!(cell.get().is_none());
-@@ -348,6 +350,7 @@ mod sync {
-
+@@ -441,6 +441,7 @@ mod sync {
#[test]
#[cfg_attr(miri, ignore)] // miri doesn't support processes
+ #[cfg(feature = "std")]
+ #[ignore = "Android: ignore for now. Need to compile these binaries separately."]
fn reentrant_init() {
let examples_dir = {
let mut exe = std::env::current_exe().unwrap();
-@@ -486,6 +489,7 @@ mod sync {
+@@ -590,6 +593,7 @@ mod sync {
}
#[test]
diff --git a/src/imp_cs.rs b/src/imp_cs.rs
new file mode 100644
index 0000000..668f18e
--- /dev/null
+++ b/src/imp_cs.rs
@@ -0,0 +1,78 @@
+use core::panic::{RefUnwindSafe, UnwindSafe};
+
+use atomic_polyfill::{AtomicBool, Ordering};
+use critical_section::{CriticalSection, Mutex};
+
+use crate::unsync;
+
+pub(crate) struct OnceCell<T> {
+ initialized: AtomicBool,
+ // Use `unsync::OnceCell` internally since `Mutex` does not provide
+ // interior mutability and to be able to re-use `get_or_try_init`.
+ value: Mutex<unsync::OnceCell<T>>,
+}
+
+// Why do we need `T: Send`?
+// Thread A creates a `OnceCell` and shares it with
+// scoped thread B, which fills the cell, which is
+// then destroyed by A. That is, destructor observes
+// a sent value.
+unsafe impl<T: Sync + Send> Sync for OnceCell<T> {}
+unsafe impl<T: Send> Send for OnceCell<T> {}
+
+impl<T: RefUnwindSafe + UnwindSafe> RefUnwindSafe for OnceCell<T> {}
+impl<T: UnwindSafe> UnwindSafe for OnceCell<T> {}
+
+impl<T> OnceCell<T> {
+ pub(crate) const fn new() -> OnceCell<T> {
+ OnceCell { initialized: AtomicBool::new(false), value: Mutex::new(unsync::OnceCell::new()) }
+ }
+
+ pub(crate) const fn with_value(value: T) -> OnceCell<T> {
+ OnceCell {
+ initialized: AtomicBool::new(true),
+ value: Mutex::new(unsync::OnceCell::with_value(value)),
+ }
+ }
+
+ #[inline]
+ pub(crate) fn is_initialized(&self) -> bool {
+ self.initialized.load(Ordering::Acquire)
+ }
+
+ #[cold]
+ pub(crate) fn initialize<F, E>(&self, f: F) -> Result<(), E>
+ where
+ F: FnOnce() -> Result<T, E>,
+ {
+ critical_section::with(|cs| {
+ let cell = self.value.borrow(cs);
+ cell.get_or_try_init(f).map(|_| {
+ self.initialized.store(true, Ordering::Release);
+ })
+ })
+ }
+
+ /// Get the reference to the underlying value, without checking if the cell
+ /// is initialized.
+ ///
+ /// # Safety
+ ///
+ /// Caller must ensure that the cell is in initialized state, and that
+ /// the contents are acquired by (synchronized to) this thread.
+ pub(crate) unsafe fn get_unchecked(&self) -> &T {
+ debug_assert!(self.is_initialized());
+ // SAFETY: The caller ensures that the value is initialized and access synchronized.
+ crate::unwrap_unchecked(self.value.borrow(CriticalSection::new()).get())
+ }
+
+ #[inline]
+ pub(crate) fn get_mut(&mut self) -> Option<&mut T> {
+ self.value.get_mut().get_mut()
+ }
+
+ #[inline]
+ pub(crate) fn into_inner(self) -> Option<T> {
+ self.value.into_inner().into_inner()
+ }
+}
diff --git a/src/imp_pl.rs b/src/imp_pl.rs
index 6c9b0fe..84d8593 100644
--- a/src/imp_pl.rs
+++ b/src/imp_pl.rs
@@ -1,20 +1,18 @@
use std::{
cell::UnsafeCell,
- hint,
panic::{RefUnwindSafe, UnwindSafe},
- sync::atomic::{AtomicBool, Ordering},
+ sync::atomic::{AtomicU8, Ordering},
};
-use parking_lot::Mutex;
-
-use crate::take_unchecked;
-
pub(crate) struct OnceCell<T> {
- mutex: Mutex<()>,
- is_initialized: AtomicBool,
+ state: AtomicU8,
value: UnsafeCell<Option<T>>,
}
+const INCOMPLETE: u8 = 0x0;
+const RUNNING: u8 = 0x1;
+const COMPLETE: u8 = 0x2;
+
// Why do we need `T: Send`?
// Thread A creates a `OnceCell` and shares it with
// scoped thread B, which fills the cell, which is
@@ -28,17 +26,17 @@ impl<T: UnwindSafe> UnwindSafe for OnceCell<T> {}
impl<T> OnceCell<T> {
pub(crate) const fn new() -> OnceCell<T> {
- OnceCell {
- mutex: parking_lot::const_mutex(()),
- is_initialized: AtomicBool::new(false),
- value: UnsafeCell::new(None),
- }
+ OnceCell { state: AtomicU8::new(INCOMPLETE), value: UnsafeCell::new(None) }
+ }
+
+ pub(crate) const fn with_value(value: T) -> OnceCell<T> {
+ OnceCell { state: AtomicU8::new(COMPLETE), value: UnsafeCell::new(Some(value)) }
}
/// Safety: synchronizes with store to value via Release/Acquire.
#[inline]
pub(crate) fn is_initialized(&self) -> bool {
- self.is_initialized.load(Ordering::Acquire)
+ self.state.load(Ordering::Acquire) == COMPLETE
}
/// Safety: synchronizes with store to value via `is_initialized` or mutex
@@ -51,7 +49,7 @@ impl<T> OnceCell<T> {
let mut f = Some(f);
let mut res: Result<(), E> = Ok(());
let slot: *mut Option<T> = self.value.get();
- initialize_inner(&self.mutex, &self.is_initialized, &mut || {
+ initialize_inner(&self.state, &mut || {
// We are calling user-supplied function and need to be careful.
// - if it returns Err, we unlock mutex and return without touching anything
// - if it panics, we unlock mutex and propagate panic without touching anything
@@ -60,7 +58,7 @@ impl<T> OnceCell<T> {
// but that is more complicated
// - finally, if it returns Ok, we store the value and store the flag with
// `Release`, which synchronizes with `Acquire`s.
- let f = unsafe { take_unchecked(&mut f) };
+ let f = unsafe { crate::unwrap_unchecked(f.take()) };
match f() {
Ok(value) => unsafe {
// Safe b/c we have a unique access and no panic may happen
@@ -78,6 +76,21 @@ impl<T> OnceCell<T> {
res
}
+ #[cold]
+ pub(crate) fn wait(&self) {
+ let key = &self.state as *const _ as usize;
+ unsafe {
+ parking_lot_core::park(
+ key,
+ || self.state.load(Ordering::Acquire) != COMPLETE,
+ || (),
+ |_, _| (),
+ parking_lot_core::DEFAULT_PARK_TOKEN,
+ None,
+ );
+ }
+ }
+
/// Get the reference to the underlying value, without checking if the cell
/// is initialized.
///
@@ -87,15 +100,8 @@ impl<T> OnceCell<T> {
/// the contents are acquired by (synchronized to) this thread.
pub(crate) unsafe fn get_unchecked(&self) -> &T {
debug_assert!(self.is_initialized());
- let slot: &Option<T> = &*self.value.get();
- match slot {
- Some(value) => value,
- // This unsafe does improve performance, see `examples/bench`.
- None => {
- debug_assert!(false);
- hint::unreachable_unchecked()
- }
- }
+ let slot = &*self.value.get();
+ crate::unwrap_unchecked(slot.as_ref())
}
/// Gets the mutable reference to the underlying value.
@@ -113,14 +119,49 @@ impl<T> OnceCell<T> {
}
}
+struct Guard<'a> {
+ state: &'a AtomicU8,
+ new_state: u8,
+}
+
+impl<'a> Drop for Guard<'a> {
+ fn drop(&mut self) {
+ self.state.store(self.new_state, Ordering::Release);
+ unsafe {
+ let key = self.state as *const AtomicU8 as usize;
+ parking_lot_core::unpark_all(key, parking_lot_core::DEFAULT_UNPARK_TOKEN);
+ }
+ }
+}
+
// Note: this is intentionally monomorphic
#[inline(never)]
-fn initialize_inner(mutex: &Mutex<()>, is_initialized: &AtomicBool, init: &mut dyn FnMut() -> bool) {
- let _guard = mutex.lock();
-
- if !is_initialized.load(Ordering::Acquire) {
- if init() {
- is_initialized.store(true, Ordering::Release);
+fn initialize_inner(state: &AtomicU8, init: &mut dyn FnMut() -> bool) {
+ loop {
+ let exchange =
+ state.compare_exchange_weak(INCOMPLETE, RUNNING, Ordering::Acquire, Ordering::Acquire);
+ match exchange {
+ Ok(_) => {
+ let mut guard = Guard { state, new_state: INCOMPLETE };
+ if init() {
+ guard.new_state = COMPLETE;
+ }
+ return;
+ }
+ Err(COMPLETE) => return,
+ Err(RUNNING) => unsafe {
+ let key = state as *const AtomicU8 as usize;
+ parking_lot_core::park(
+ key,
+ || state.load(Ordering::Relaxed) == RUNNING,
+ || (),
+ |_, _| (),
+ parking_lot_core::DEFAULT_PARK_TOKEN,
+ None,
+ );
+ },
+ Err(INCOMPLETE) => (),
+ Err(_) => debug_assert!(false),
}
}
}
@@ -129,5 +170,5 @@ fn initialize_inner(mutex: &Mutex<()>, is_initialized: &AtomicBool, init: &mut d
fn test_size() {
use std::mem::size_of;
- assert_eq!(size_of::<OnceCell<bool>>(), 2 * size_of::<bool>() + size_of::<u8>());
+ assert_eq!(size_of::<OnceCell<bool>>(), 1 * size_of::<bool>() + size_of::<u8>());
}
diff --git a/src/imp_std.rs b/src/imp_std.rs
index f461c3d..d727851 100644
--- a/src/imp_std.rs
+++ b/src/imp_std.rs
@@ -5,20 +5,23 @@
use std::{
cell::{Cell, UnsafeCell},
- hint::unreachable_unchecked,
marker::PhantomData,
panic::{RefUnwindSafe, UnwindSafe},
- sync::atomic::{AtomicBool, AtomicUsize, Ordering},
+ sync::atomic::{AtomicBool, AtomicPtr, Ordering},
thread::{self, Thread},
};
-use crate::take_unchecked;
-
#[derive(Debug)]
pub(crate) struct OnceCell<T> {
- // This `state` word is actually an encoded version of just a pointer to a
- // `Waiter`, so we add the `PhantomData` appropriately.
- state_and_queue: AtomicUsize,
+ // This `queue` field is the core of the implementation. It encodes two
+ // pieces of information:
+ //
+ // * The current state of the cell (`INCOMPLETE`, `RUNNING`, `COMPLETE`)
+ // * Linked list of threads waiting for the current cell.
+ //
+ // State is encoded in two low bits. Only `INCOMPLETE` and `RUNNING` states
+ // allow waiters.
+ queue: AtomicPtr<Waiter>,
_marker: PhantomData<*mut Waiter>,
value: UnsafeCell<Option<T>>,
}
@@ -34,41 +37,23 @@ unsafe impl<T: Send> Send for OnceCell<T> {}
impl<T: RefUnwindSafe + UnwindSafe> RefUnwindSafe for OnceCell<T> {}
impl<T: UnwindSafe> UnwindSafe for OnceCell<T> {}
-// Three states that a OnceCell can be in, encoded into the lower bits of `state` in
-// the OnceCell structure.
-const INCOMPLETE: usize = 0x0;
-const RUNNING: usize = 0x1;
-const COMPLETE: usize = 0x2;
-
-// Mask to learn about the state. All other bits are the queue of waiters if
-// this is in the RUNNING state.
-const STATE_MASK: usize = 0x3;
-
-// Representation of a node in the linked list of waiters in the RUNNING state.
-#[repr(align(4))] // Ensure the two lower bits are free to use as state bits.
-struct Waiter {
- thread: Cell<Option<Thread>>,
- signaled: AtomicBool,
- next: *const Waiter,
-}
-
-// Head of a linked list of waiters.
-// Every node is a struct on the stack of a waiting thread.
-// Will wake up the waiters when it gets dropped, i.e. also on panic.
-struct WaiterQueue<'a> {
- state_and_queue: &'a AtomicUsize,
- set_state_on_drop_to: usize,
-}
-
impl<T> OnceCell<T> {
pub(crate) const fn new() -> OnceCell<T> {
OnceCell {
- state_and_queue: AtomicUsize::new(INCOMPLETE),
+ queue: AtomicPtr::new(INCOMPLETE_PTR),
_marker: PhantomData,
value: UnsafeCell::new(None),
}
}
+ pub(crate) const fn with_value(value: T) -> OnceCell<T> {
+ OnceCell {
+ queue: AtomicPtr::new(COMPLETE_PTR),
+ _marker: PhantomData,
+ value: UnsafeCell::new(Some(value)),
+ }
+ }
+
/// Safety: synchronizes with store to value via Release/(Acquire|SeqCst).
#[inline]
pub(crate) fn is_initialized(&self) -> bool {
@@ -76,7 +61,7 @@ impl<T> OnceCell<T> {
// operations visible to us, and, this being a fast path, weaker
// ordering helps with performance. This `Acquire` synchronizes with
// `SeqCst` operations on the slow path.
- self.state_and_queue.load(Ordering::Acquire) == COMPLETE
+ self.queue.load(Ordering::Acquire) == COMPLETE_PTR
}
/// Safety: synchronizes with store to value via SeqCst read from state,
@@ -90,22 +75,30 @@ impl<T> OnceCell<T> {
let mut f = Some(f);
let mut res: Result<(), E> = Ok(());
let slot: *mut Option<T> = self.value.get();
- initialize_inner(&self.state_and_queue, &mut || {
- let f = unsafe { take_unchecked(&mut f) };
- match f() {
- Ok(value) => {
- unsafe { *slot = Some(value) };
- true
+ initialize_or_wait(
+ &self.queue,
+ Some(&mut || {
+ let f = unsafe { crate::unwrap_unchecked(f.take()) };
+ match f() {
+ Ok(value) => {
+ unsafe { *slot = Some(value) };
+ true
+ }
+ Err(err) => {
+ res = Err(err);
+ false
+ }
}
- Err(err) => {
- res = Err(err);
- false
- }
- }
- });
+ }),
+ );
res
}
+ #[cold]
+ pub(crate) fn wait(&self) {
+ initialize_or_wait(&self.queue, None);
+ }
+
/// Get the reference to the underlying value, without checking if the cell
/// is initialized.
///
@@ -115,15 +108,8 @@ impl<T> OnceCell<T> {
/// the contents are acquired by (synchronized to) this thread.
pub(crate) unsafe fn get_unchecked(&self) -> &T {
debug_assert!(self.is_initialized());
- let slot: &Option<T> = &*self.value.get();
- match slot {
- Some(value) => value,
- // This unsafe does improve performance, see `examples/bench`.
- None => {
- debug_assert!(false);
- unreachable_unchecked()
- }
- }
+ let slot = &*self.value.get();
+ crate::unwrap_unchecked(slot.as_ref())
}
/// Gets the mutable reference to the underlying value.
@@ -144,67 +130,114 @@ impl<T> OnceCell<T> {
}
}
-// Corresponds to `std::sync::Once::call_inner`
+// Three states that a OnceCell can be in, encoded into the lower bits of `queue` in
+// the OnceCell structure.
+const INCOMPLETE: usize = 0x0;
+const RUNNING: usize = 0x1;
+const COMPLETE: usize = 0x2;
+const INCOMPLETE_PTR: *mut Waiter = INCOMPLETE as *mut Waiter;
+const COMPLETE_PTR: *mut Waiter = COMPLETE as *mut Waiter;
+
+// Mask to learn about the state. All other bits are the queue of waiters if
+// this is in the RUNNING state.
+const STATE_MASK: usize = 0x3;
+
+/// Representation of a node in the linked list of waiters in the RUNNING state.
+/// A waiters is stored on the stack of the waiting threads.
+#[repr(align(4))] // Ensure the two lower bits are free to use as state bits.
+struct Waiter {
+ thread: Cell<Option<Thread>>,
+ signaled: AtomicBool,
+ next: *mut Waiter,
+}
+
+/// Drains and notifies the queue of waiters on drop.
+struct Guard<'a> {
+ queue: &'a AtomicPtr<Waiter>,
+ new_queue: *mut Waiter,
+}
+
+impl Drop for Guard<'_> {
+ fn drop(&mut self) {
+ let queue = self.queue.swap(self.new_queue, Ordering::AcqRel);
+
+ let state = strict::addr(queue) & STATE_MASK;
+ assert_eq!(state, RUNNING);
+
+ unsafe {
+ let mut waiter = strict::map_addr(queue, |q| q & !STATE_MASK);
+ while !waiter.is_null() {
+ let next = (*waiter).next;
+ let thread = (*waiter).thread.take().unwrap();
+ (*waiter).signaled.store(true, Ordering::Release);
+ waiter = next;
+ thread.unpark();
+ }
+ }
+ }
+}
+
+// Corresponds to `std::sync::Once::call_inner`.
+//
+// Originally copied from std, but since modified to remove poisoning and to
+// support wait.
+//
// Note: this is intentionally monomorphic
#[inline(never)]
-fn initialize_inner(my_state_and_queue: &AtomicUsize, init: &mut dyn FnMut() -> bool) -> bool {
- let mut state_and_queue = my_state_and_queue.load(Ordering::Acquire);
+fn initialize_or_wait(queue: &AtomicPtr<Waiter>, mut init: Option<&mut dyn FnMut() -> bool>) {
+ let mut curr_queue = queue.load(Ordering::Acquire);
loop {
- match state_and_queue {
- COMPLETE => return true,
- INCOMPLETE => {
- let exchange = my_state_and_queue.compare_exchange(
- state_and_queue,
- RUNNING,
+ let curr_state = strict::addr(curr_queue) & STATE_MASK;
+ match (curr_state, &mut init) {
+ (COMPLETE, _) => return,
+ (INCOMPLETE, Some(init)) => {
+ let exchange = queue.compare_exchange(
+ curr_queue,
+ strict::map_addr(curr_queue, |q| (q & !STATE_MASK) | RUNNING),
Ordering::Acquire,
Ordering::Acquire,
);
- if let Err(old) = exchange {
- state_and_queue = old;
+ if let Err(new_queue) = exchange {
+ curr_queue = new_queue;
continue;
}
- let mut waiter_queue = WaiterQueue {
- state_and_queue: my_state_and_queue,
- set_state_on_drop_to: INCOMPLETE, // Difference, std uses `POISONED`
- };
- let success = init();
-
- // Difference, std always uses `COMPLETE`
- waiter_queue.set_state_on_drop_to = if success { COMPLETE } else { INCOMPLETE };
- return success;
+ let mut guard = Guard { queue, new_queue: INCOMPLETE_PTR };
+ if init() {
+ guard.new_queue = COMPLETE_PTR;
+ }
+ return;
}
- _ => {
- assert!(state_and_queue & STATE_MASK == RUNNING);
- wait(&my_state_and_queue, state_and_queue);
- state_and_queue = my_state_and_queue.load(Ordering::Acquire);
+ (INCOMPLETE, None) | (RUNNING, _) => {
+ wait(&queue, curr_queue);
+ curr_queue = queue.load(Ordering::Acquire);
}
+ _ => debug_assert!(false),
}
}
}
-// Copy-pasted from std exactly.
-fn wait(state_and_queue: &AtomicUsize, mut current_state: usize) {
+fn wait(queue: &AtomicPtr<Waiter>, mut curr_queue: *mut Waiter) {
+ let curr_state = strict::addr(curr_queue) & STATE_MASK;
loop {
- if current_state & STATE_MASK != RUNNING {
- return;
- }
-
let node = Waiter {
thread: Cell::new(Some(thread::current())),
signaled: AtomicBool::new(false),
- next: (current_state & !STATE_MASK) as *const Waiter,
+ next: strict::map_addr(curr_queue, |q| q & !STATE_MASK),
};
- let me = &node as *const Waiter as usize;
+ let me = &node as *const Waiter as *mut Waiter;
- let exchange = state_and_queue.compare_exchange(
- current_state,
- me | RUNNING,
+ let exchange = queue.compare_exchange(
+ curr_queue,
+ strict::map_addr(me, |q| q | curr_state),
Ordering::Release,
Ordering::Relaxed,
);
- if let Err(old) = exchange {
- current_state = old;
+ if let Err(new_queue) = exchange {
+ if strict::addr(new_queue) & STATE_MASK != curr_state {
+ return;
+ }
+ curr_queue = new_queue;
continue;
}
@@ -215,24 +248,51 @@ fn wait(state_and_queue: &AtomicUsize, mut current_state: usize) {
}
}
-// Copy-pasted from std exactly.
-impl Drop for WaiterQueue<'_> {
- fn drop(&mut self) {
- let state_and_queue =
- self.state_and_queue.swap(self.set_state_on_drop_to, Ordering::AcqRel);
+// Polyfill of strict provenance from https://crates.io/crates/sptr.
+//
+// Use free-standing function rather than a trait to keep things simple and
+// avoid any potential conflicts with future stabile std API.
+mod strict {
+ #[must_use]
+ #[inline]
+ pub(crate) fn addr<T>(ptr: *mut T) -> usize
+ where
+ T: Sized,
+ {
+ // FIXME(strict_provenance_magic): I am magic and should be a compiler intrinsic.
+ // SAFETY: Pointer-to-integer transmutes are valid (if you are okay with losing the
+ // provenance).
+ unsafe { core::mem::transmute(ptr) }
+ }
- assert_eq!(state_and_queue & STATE_MASK, RUNNING);
+ #[must_use]
+ #[inline]
+ pub(crate) fn with_addr<T>(ptr: *mut T, addr: usize) -> *mut T
+ where
+ T: Sized,
+ {
+ // FIXME(strict_provenance_magic): I am magic and should be a compiler intrinsic.
+ //
+ // In the mean-time, this operation is defined to be "as if" it was
+ // a wrapping_offset, so we can emulate it as such. This should properly
+ // restore pointer provenance even under today's compiler.
+ let self_addr = self::addr(ptr) as isize;
+ let dest_addr = addr as isize;
+ let offset = dest_addr.wrapping_sub(self_addr);
+
+ // This is the canonical desugarring of this operation,
+ // but `pointer::cast` was only stabilized in 1.38.
+ // self.cast::<u8>().wrapping_offset(offset).cast::<T>()
+ (ptr as *mut u8).wrapping_offset(offset) as *mut T
+ }
- unsafe {
- let mut queue = (state_and_queue & !STATE_MASK) as *const Waiter;
- while !queue.is_null() {
- let next = (*queue).next;
- let thread = (*queue).thread.replace(None).unwrap();
- (*queue).signaled.store(true, Ordering::Release);
- queue = next;
- thread.unpark();
- }
- }
+ #[must_use]
+ #[inline]
+ pub(crate) fn map_addr<T>(ptr: *mut T, f: impl FnOnce(usize) -> usize) -> *mut T
+ where
+ T: Sized,
+ {
+ self::with_addr(ptr, f(addr(ptr)))
}
}
@@ -262,7 +322,6 @@ mod tests {
}
#[test]
- #[cfg(not(miri))]
fn stampede_once() {
static O: OnceCell<()> = OnceCell::new();
static mut RUN: bool = false;
diff --git a/src/lib.rs b/src/lib.rs
index cb8bfc7..c2061f8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -208,7 +208,6 @@
//! ```
//! use once_cell::sync::OnceCell;
//!
-//! #[derive(Debug)]
//! pub struct LateInit<T> { cell: OnceCell<T> }
//!
//! impl<T> LateInit<T> {
@@ -228,22 +227,24 @@
//! }
//! }
//!
-//! #[derive(Default, Debug)]
+//! #[derive(Default)]
//! struct A<'a> {
//! b: LateInit<&'a B<'a>>,
//! }
//!
-//! #[derive(Default, Debug)]
+//! #[derive(Default)]
//! struct B<'a> {
//! a: LateInit<&'a A<'a>>
//! }
//!
+//!
//! fn build_cycle() {
//! let a = A::default();
//! let b = B::default();
//! a.b.init(&b);
//! b.a.init(&a);
-//! println!("{:?}", a.b.a.b.a);
+//!
+//! let _a = &a.b.a.b.a;
//! }
//! ```
//!
@@ -267,9 +268,9 @@
//!
//! # Minimum Supported `rustc` Version
//!
-//! This crate's minimum supported `rustc` version is `1.36.0`.
+//! This crate's minimum supported `rustc` version is `1.56.0`.
//!
-//! If only the `std` feature is enabled, MSRV will be updated conservatively.
+//! If only the `std` feature is enabled, MSRV will be updated conservatively, supporting at least latest 8 versions of the compiler.
//! When using other features, like `parking_lot`, MSRV might be updated more frequently, up to the latest stable.
//! In both cases, increasing MSRV is *not* considered a semver-breaking change.
//!
@@ -311,6 +312,14 @@
//! At the moment, `unsync` has an additional benefit that reentrant initialization causes a panic, which
//! might be easier to debug than a deadlock.
//!
+//! **Does this crate support async?**
+//!
+//! No, but you can use [`async_once_cell`](https://crates.io/crates/async_once_cell) instead.
+//!
+//! **Can I bring my own mutex?**
+//!
+//! There is [generic_once_cell](https://crates.io/crates/generic_once_cell) to allow just that.
+//!
//! # Related crates
//!
//! * [double-checked-cell](https://github.com/niklasf/double-checked-cell)
@@ -318,6 +327,8 @@
//! * [lazycell](https://crates.io/crates/lazycell)
//! * [mitochondria](https://crates.io/crates/mitochondria)
//! * [lazy_static](https://crates.io/crates/lazy_static)
+//! * [async_once_cell](https://crates.io/crates/async_once_cell)
+//! * [generic_once_cell](https://crates.io/crates/generic_once_cell) (bring your own mutex)
//!
//! Most of this crate's functionality is available in `std` in nightly Rust.
//! See the [tracking issue](https://github.com/rust-lang/rust/issues/74465).
@@ -327,13 +338,15 @@
#[cfg(feature = "alloc")]
extern crate alloc;
-#[cfg(feature = "std")]
-#[cfg(feature = "parking_lot")]
+#[cfg(all(feature = "critical-section", not(feature = "std")))]
+#[path = "imp_cs.rs"]
+mod imp;
+
+#[cfg(all(feature = "std", feature = "parking_lot"))]
#[path = "imp_pl.rs"]
mod imp;
-#[cfg(feature = "std")]
-#[cfg(not(feature = "parking_lot"))]
+#[cfg(all(feature = "std", not(feature = "parking_lot")))]
#[path = "imp_std.rs"]
mod imp;
@@ -341,12 +354,12 @@ mod imp;
pub mod unsync {
use core::{
cell::{Cell, UnsafeCell},
- fmt, hint, mem,
+ fmt, mem,
ops::{Deref, DerefMut},
+ panic::{RefUnwindSafe, UnwindSafe},
};
- #[cfg(feature = "std")]
- use std::panic::{RefUnwindSafe, UnwindSafe};
+ use super::unwrap_unchecked;
/// A cell which can be written to only once. It is not thread safe.
///
@@ -377,9 +390,7 @@ pub mod unsync {
// `&unsync::OnceCell` to sneak a `T` through `catch_unwind`,
// by initializing the cell in closure and extracting the value in the
// `Drop`.
- #[cfg(feature = "std")]
impl<T: RefUnwindSafe + UnwindSafe> RefUnwindSafe for OnceCell<T> {}
- #[cfg(feature = "std")]
impl<T: UnwindSafe> UnwindSafe for OnceCell<T> {}
impl<T> Default for OnceCell<T> {
@@ -399,14 +410,17 @@ pub mod unsync {
impl<T: Clone> Clone for OnceCell<T> {
fn clone(&self) -> OnceCell<T> {
- let res = OnceCell::new();
- if let Some(value) = self.get() {
- match res.set(value.clone()) {
- Ok(()) => (),
- Err(_) => unreachable!(),
- }
+ match self.get() {
+ Some(value) => OnceCell::with_value(value.clone()),
+ None => OnceCell::new(),
+ }
+ }
+
+ fn clone_from(&mut self, source: &Self) {
+ match (self.get_mut(), source.get()) {
+ (Some(this), Some(source)) => this.clone_from(source),
+ _ => *self = source.clone(),
}
- res
}
}
@@ -420,7 +434,7 @@ pub mod unsync {
impl<T> From<T> for OnceCell<T> {
fn from(value: T) -> Self {
- OnceCell { inner: UnsafeCell::new(Some(value)) }
+ OnceCell::with_value(value)
}
}
@@ -430,11 +444,20 @@ pub mod unsync {
OnceCell { inner: UnsafeCell::new(None) }
}
+ /// Creates a new initialized cell.
+ pub const fn with_value(value: T) -> OnceCell<T> {
+ OnceCell { inner: UnsafeCell::new(Some(value)) }
+ }
+
/// Gets a reference to the underlying value.
///
/// Returns `None` if the cell is empty.
+ #[inline]
pub fn get(&self) -> Option<&T> {
- // Safe due to `inner`'s invariant
+ // Safe due to `inner`'s invariant of being written to at most once.
+ // Had multiple writes to `inner` been allowed, a reference to the
+ // value we return now would become dangling by a write of a
+ // different value later.
unsafe { &*self.inner.get() }.as_ref()
}
@@ -451,8 +474,10 @@ pub mod unsync {
///
/// let mut cell: OnceCell<u32> = OnceCell::new();
/// cell.set(92).unwrap();
- /// cell = OnceCell::new();
+ /// *cell.get_mut().unwrap() = 93;
+ /// assert_eq!(cell.get(), Some(&93));
/// ```
+ #[inline]
pub fn get_mut(&mut self) -> Option<&mut T> {
// Safe because we have unique access
unsafe { &mut *self.inner.get() }.as_mut()
@@ -482,7 +507,7 @@ pub mod unsync {
}
}
- /// Like [`set`](Self::set), but also returns a referce to the final cell value.
+ /// Like [`set`](Self::set), but also returns a reference to the final cell value.
///
/// # Example
/// ```
@@ -500,16 +525,14 @@ pub mod unsync {
if let Some(old) = self.get() {
return Err((old, value));
}
+
let slot = unsafe { &mut *self.inner.get() };
// This is the only place where we set the slot, no races
// due to reentrancy/concurrency are possible, and we've
// checked that slot is currently `None`, so this write
// maintains the `inner`'s invariant.
*slot = Some(value);
- Ok(match &*slot {
- Some(value) => value,
- None => unsafe { hint::unreachable_unchecked() },
- })
+ Ok(unsafe { unwrap_unchecked(slot.as_ref()) })
}
/// Gets the contents of the cell, initializing it with `f`
@@ -582,7 +605,7 @@ pub mod unsync {
// `assert`, while keeping `set/get` would be sound, but it seems
// better to panic, rather than to silently use an old value.
assert!(self.set(val).is_ok(), "reentrant init");
- Ok(self.get().unwrap())
+ Ok(unsafe { unwrap_unchecked(self.get()) })
}
/// Takes the value out of this `OnceCell`, moving it back to an uninitialized state.
@@ -666,7 +689,6 @@ pub mod unsync {
init: Cell<Option<F>>,
}
- #[cfg(feature = "std")]
impl<T, F: RefUnwindSafe> RefUnwindSafe for Lazy<T, F> where OnceCell<T>: RefUnwindSafe {}
impl<T: fmt::Debug, F> fmt::Debug for Lazy<T, F> {
@@ -727,6 +749,59 @@ pub mod unsync {
None => panic!("Lazy instance has previously been poisoned"),
})
}
+
+ /// Forces the evaluation of this lazy value and returns a mutable reference to
+ /// the result.
+ ///
+ /// This is equivalent to the `DerefMut` impl, but is explicit.
+ ///
+ /// # Example
+ /// ```
+ /// use once_cell::unsync::Lazy;
+ ///
+ /// let mut lazy = Lazy::new(|| 92);
+ ///
+ /// assert_eq!(Lazy::force_mut(&mut lazy), &92);
+ /// assert_eq!(*lazy, 92);
+ /// ```
+ pub fn force_mut(this: &mut Lazy<T, F>) -> &mut T {
+ Self::force(this);
+ Self::get_mut(this).unwrap_or_else(|| unreachable!())
+ }
+
+ /// Gets the reference to the result of this lazy value if
+ /// it was initialized, otherwise returns `None`.
+ ///
+ /// # Example
+ /// ```
+ /// use once_cell::unsync::Lazy;
+ ///
+ /// let lazy = Lazy::new(|| 92);
+ ///
+ /// assert_eq!(Lazy::get(&lazy), None);
+ /// assert_eq!(&*lazy, &92);
+ /// assert_eq!(Lazy::get(&lazy), Some(&92));
+ /// ```
+ pub fn get(this: &Lazy<T, F>) -> Option<&T> {
+ this.cell.get()
+ }
+
+ /// Gets the mutable reference to the result of this lazy value if
+ /// it was initialized, otherwise returns `None`.
+ ///
+ /// # Example
+ /// ```
+ /// use once_cell::unsync::Lazy;
+ ///
+ /// let mut lazy = Lazy::new(|| 92);
+ ///
+ /// assert_eq!(Lazy::get_mut(&mut lazy), None);
+ /// assert_eq!(*lazy, 92);
+ /// assert_eq!(Lazy::get_mut(&mut lazy), Some(&mut 92));
+ /// ```
+ pub fn get_mut(this: &mut Lazy<T, F>) -> Option<&mut T> {
+ this.cell.get_mut()
+ }
}
impl<T, F: FnOnce() -> T> Deref for Lazy<T, F> {
@@ -752,16 +827,16 @@ pub mod unsync {
}
/// Thread-safe, blocking version of `OnceCell`.
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "critical-section"))]
pub mod sync {
- use std::{
+ use core::{
cell::Cell,
fmt, mem,
ops::{Deref, DerefMut},
panic::RefUnwindSafe,
};
- use crate::{imp::OnceCell as Imp, take_unchecked};
+ use super::{imp::OnceCell as Imp, unwrap_unchecked};
/// A thread-safe cell which can be written to only once.
///
@@ -810,22 +885,23 @@ pub mod sync {
impl<T: Clone> Clone for OnceCell<T> {
fn clone(&self) -> OnceCell<T> {
- let res = OnceCell::new();
- if let Some(value) = self.get() {
- match res.set(value.clone()) {
- Ok(()) => (),
- Err(_) => unreachable!(),
- }
+ match self.get() {
+ Some(value) => Self::with_value(value.clone()),
+ None => Self::new(),
+ }
+ }
+
+ fn clone_from(&mut self, source: &Self) {
+ match (self.get_mut(), source.get()) {
+ (Some(this), Some(source)) => this.clone_from(source),
+ _ => *self = source.clone(),
}
- res
}
}
impl<T> From<T> for OnceCell<T> {
fn from(value: T) -> Self {
- let cell = Self::new();
- cell.get_or_init(|| value);
- cell
+ Self::with_value(value)
}
}
@@ -843,6 +919,11 @@ pub mod sync {
OnceCell(Imp::new())
}
+ /// Creates a new initialized cell.
+ pub const fn with_value(value: T) -> OnceCell<T> {
+ OnceCell(Imp::with_value(value))
+ }
+
/// Gets the reference to the underlying value.
///
/// Returns `None` if the cell is empty, or being initialized. This
@@ -856,6 +937,37 @@ pub mod sync {
}
}
+ /// Gets the reference to the underlying value, blocking the current
+ /// thread until it is set.
+ ///
+ /// ```
+ /// use once_cell::sync::OnceCell;
+ ///
+ /// let mut cell = std::sync::Arc::new(OnceCell::new());
+ /// let t = std::thread::spawn({
+ /// let cell = std::sync::Arc::clone(&cell);
+ /// move || cell.set(92).unwrap()
+ /// });
+ ///
+ /// // Returns immediately, but might return None.
+ /// let _value_or_none = cell.get();
+ ///
+ /// // Will return 92, but might block until the other thread does `.set`.
+ /// let value: &u32 = cell.wait();
+ /// assert_eq!(*value, 92);
+ /// t.join().unwrap();
+ /// ```
+ #[cfg(feature = "std")]
+ pub fn wait(&self) -> &T {
+ if !self.0.is_initialized() {
+ self.0.wait()
+ }
+ debug_assert!(self.0.is_initialized());
+ // Safe b/c of the wait call above and the fact that we didn't
+ // relinquish our borrow.
+ unsafe { self.get_unchecked() }
+ }
+
/// Gets the mutable reference to the underlying value.
///
/// Returns `None` if the cell is empty.
@@ -871,6 +983,7 @@ pub mod sync {
/// cell.set(92).unwrap();
/// cell = OnceCell::new();
/// ```
+ #[inline]
pub fn get_mut(&mut self) -> Option<&mut T> {
self.0.get_mut()
}
@@ -882,6 +995,7 @@ pub mod sync {
///
/// Caller must ensure that the cell is in initialized state, and that
/// the contents are acquired by (synchronized to) this thread.
+ #[inline]
pub unsafe fn get_unchecked(&self) -> &T {
self.0.get_unchecked()
}
@@ -933,7 +1047,7 @@ pub mod sync {
/// ```
pub fn try_insert(&self, value: T) -> Result<&T, (&T, T)> {
let mut value = Some(value);
- let res = self.get_or_init(|| unsafe { take_unchecked(&mut value) });
+ let res = self.get_or_init(|| unsafe { unwrap_unchecked(value.take()) });
match value {
None => Ok(res),
Some(value) => Err((res, value)),
@@ -1011,6 +1125,7 @@ pub mod sync {
if let Some(value) = self.get() {
return Ok(value);
}
+
self.0.initialize(f)?;
// Safe b/c value is initialized.
@@ -1066,6 +1181,7 @@ pub mod sync {
/// cell.set("hello".to_string()).unwrap();
/// assert_eq!(cell.into_inner(), Some("hello".to_string()));
/// ```
+ #[inline]
pub fn into_inner(self) -> Option<T> {
self.0.into_inner()
}
@@ -1116,13 +1232,12 @@ pub mod sync {
}
// We never create a `&F` from a `&Lazy<T, F>` so it is fine to not impl
- // `Sync` for `F`. we do create a `&mut Option<F>` in `force`, but this is
+ // `Sync` for `F`. We do create a `&mut Option<F>` in `force`, but this is
// properly synchronized, so it only happens once so it also does not
// contribute to this impl.
unsafe impl<T, F: Send> Sync for Lazy<T, F> where OnceCell<T>: Sync {}
// auto-derived `Send` impl is OK.
- #[cfg(feature = "std")]
impl<T, F: RefUnwindSafe> RefUnwindSafe for Lazy<T, F> where OnceCell<T>: RefUnwindSafe {}
impl<T, F> Lazy<T, F> {
@@ -1164,6 +1279,57 @@ pub mod sync {
None => panic!("Lazy instance has previously been poisoned"),
})
}
+
+ /// Forces the evaluation of this lazy value and
+ /// returns a mutable reference to the result. This is equivalent
+ /// to the `Deref` impl, but is explicit.
+ ///
+ /// # Example
+ /// ```
+ /// use once_cell::sync::Lazy;
+ ///
+ /// let mut lazy = Lazy::new(|| 92);
+ ///
+ /// assert_eq!(Lazy::force_mut(&mut lazy), &mut 92);
+ /// ```
+ pub fn force_mut(this: &mut Lazy<T, F>) -> &mut T {
+ Self::force(this);
+ Self::get_mut(this).unwrap_or_else(|| unreachable!())
+ }
+
+ /// Gets the reference to the result of this lazy value if
+ /// it was initialized, otherwise returns `None`.
+ ///
+ /// # Example
+ /// ```
+ /// use once_cell::sync::Lazy;
+ ///
+ /// let lazy = Lazy::new(|| 92);
+ ///
+ /// assert_eq!(Lazy::get(&lazy), None);
+ /// assert_eq!(&*lazy, &92);
+ /// assert_eq!(Lazy::get(&lazy), Some(&92));
+ /// ```
+ pub fn get(this: &Lazy<T, F>) -> Option<&T> {
+ this.cell.get()
+ }
+
+ /// Gets the reference to the result of this lazy value if
+ /// it was initialized, otherwise returns `None`.
+ ///
+ /// # Example
+ /// ```
+ /// use once_cell::sync::Lazy;
+ ///
+ /// let mut lazy = Lazy::new(|| 92);
+ ///
+ /// assert_eq!(Lazy::get_mut(&mut lazy), None);
+ /// assert_eq!(&*lazy, &92);
+ /// assert_eq!(Lazy::get_mut(&mut lazy), Some(&mut 92));
+ /// ```
+ pub fn get_mut(this: &mut Lazy<T, F>) -> Option<&mut T> {
+ this.cell.get_mut()
+ }
}
impl<T, F: FnOnce() -> T> Deref for Lazy<T, F> {
@@ -1208,13 +1374,14 @@ pub mod sync {
#[cfg(feature = "race")]
pub mod race;
-#[cfg(feature = "std")]
-unsafe fn take_unchecked<T>(val: &mut Option<T>) -> T {
- match val.take() {
- Some(it) => it,
+// Remove once MSRV is at least 1.58.
+#[inline]
+unsafe fn unwrap_unchecked<T>(val: Option<T>) -> T {
+ match val {
+ Some(value) => value,
None => {
debug_assert!(false);
- std::hint::unreachable_unchecked()
+ core::hint::unreachable_unchecked()
}
}
}
diff --git a/src/race.rs b/src/race.rs
index 3576420..ee3d51a 100644
--- a/src/race.rs
+++ b/src/race.rs
@@ -5,14 +5,30 @@
//! them stores the result.
//!
//! This module does not require `std` feature.
+//!
+//! # Atomic orderings
+//!
+//! All types in this module use `Acquire` and `Release`
+//! [atomic orderings](Ordering) for all their operations. While this is not
+//! strictly necessary for types other than `OnceBox`, it is useful for users as
+//! it allows them to be certain that after `get` or `get_or_init` returns on
+//! one thread, any side-effects caused by the setter thread prior to them
+//! calling `set` or `get_or_init` will be made visible to that thread; without
+//! it, it's possible for it to appear as if they haven't happened yet from the
+//! getter thread's perspective. This is an acceptable tradeoff to make since
+//! `Acquire` and `Release` have very little performance overhead on most
+//! architectures versus `Relaxed`.
-#[cfg(feature = "atomic-polyfill")]
+#[cfg(feature = "critical-section")]
use atomic_polyfill as atomic;
-#[cfg(not(feature = "atomic-polyfill"))]
+#[cfg(not(feature = "critical-section"))]
use core::sync::atomic;
-use atomic::{AtomicUsize, Ordering};
+use atomic::{AtomicPtr, AtomicUsize, Ordering};
+use core::cell::UnsafeCell;
+use core::marker::PhantomData;
use core::num::NonZeroUsize;
+use core::ptr;
/// A thread-safe cell which can be written to only once.
#[derive(Default, Debug)]
@@ -152,12 +168,125 @@ impl OnceBool {
fn from_usize(value: NonZeroUsize) -> bool {
value.get() == 1
}
+
#[inline]
fn to_usize(value: bool) -> NonZeroUsize {
unsafe { NonZeroUsize::new_unchecked(if value { 1 } else { 2 }) }
}
}
+/// A thread-safe cell which can be written to only once.
+pub struct OnceRef<'a, T> {
+ inner: AtomicPtr<T>,
+ ghost: PhantomData<UnsafeCell<&'a T>>,
+}
+
+// TODO: Replace UnsafeCell with SyncUnsafeCell once stabilized
+unsafe impl<'a, T: Sync> Sync for OnceRef<'a, T> {}
+
+impl<'a, T> core::fmt::Debug for OnceRef<'a, T> {
+ fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+ write!(f, "OnceRef({:?})", self.inner)
+ }
+}
+
+impl<'a, T> Default for OnceRef<'a, T> {
+ fn default() -> Self {
+ Self::new()
+ }
+}
+
+impl<'a, T> OnceRef<'a, T> {
+ /// Creates a new empty cell.
+ pub const fn new() -> OnceRef<'a, T> {
+ OnceRef { inner: AtomicPtr::new(ptr::null_mut()), ghost: PhantomData }
+ }
+
+ /// Gets a reference to the underlying value.
+ pub fn get(&self) -> Option<&'a T> {
+ let ptr = self.inner.load(Ordering::Acquire);
+ unsafe { ptr.as_ref() }
+ }
+
+ /// Sets the contents of this cell to `value`.
+ ///
+ /// Returns `Ok(())` if the cell was empty and `Err(value)` if it was
+ /// full.
+ pub fn set(&self, value: &'a T) -> Result<(), ()> {
+ let ptr = value as *const T as *mut T;
+ let exchange =
+ self.inner.compare_exchange(ptr::null_mut(), ptr, Ordering::AcqRel, Ordering::Acquire);
+ match exchange {
+ Ok(_) => Ok(()),
+ Err(_) => Err(()),
+ }
+ }
+
+ /// Gets the contents of the cell, initializing it with `f` if the cell was
+ /// empty.
+ ///
+ /// If several threads concurrently run `get_or_init`, more than one `f` can
+ /// be called. However, all threads will return the same value, produced by
+ /// some `f`.
+ pub fn get_or_init<F>(&self, f: F) -> &'a T
+ where
+ F: FnOnce() -> &'a T,
+ {
+ enum Void {}
+ match self.get_or_try_init(|| Ok::<&'a T, Void>(f())) {
+ Ok(val) => val,
+ Err(void) => match void {},
+ }
+ }
+
+ /// Gets the contents of the cell, initializing it with `f` if
+ /// the cell was empty. If the cell was empty and `f` failed, an
+ /// error is returned.
+ ///
+ /// If several threads concurrently run `get_or_init`, more than one `f` can
+ /// be called. However, all threads will return the same value, produced by
+ /// some `f`.
+ pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&'a T, E>
+ where
+ F: FnOnce() -> Result<&'a T, E>,
+ {
+ let mut ptr = self.inner.load(Ordering::Acquire);
+
+ if ptr.is_null() {
+ // TODO replace with `cast_mut` when MSRV reaches 1.65.0 (also in `set`)
+ ptr = f()? as *const T as *mut T;
+ let exchange = self.inner.compare_exchange(
+ ptr::null_mut(),
+ ptr,
+ Ordering::AcqRel,
+ Ordering::Acquire,
+ );
+ if let Err(old) = exchange {
+ ptr = old;
+ }
+ }
+
+ Ok(unsafe { &*ptr })
+ }
+
+ /// ```compile_fail
+ /// use once_cell::race::OnceRef;
+ ///
+ /// let mut l = OnceRef::new();
+ ///
+ /// {
+ /// let y = 2;
+ /// let mut r = OnceRef::new();
+ /// r.set(&y).unwrap();
+ /// core::mem::swap(&mut l, &mut r);
+ /// }
+ ///
+ /// // l now contains a dangling reference to y
+ /// eprintln!("uaf: {}", l.get().unwrap());
+ /// ```
+ fn _dummy() {}
+}
+
#[cfg(feature = "alloc")]
pub use self::once_box::OnceBox;
diff --git a/tests/it.rs b/tests/it.rs
index c769487..ec35e4b 100644
--- a/tests/it.rs
+++ b/tests/it.rs
@@ -18,6 +18,13 @@ mod unsync {
}
#[test]
+ fn once_cell_with_value() {
+ const CELL: OnceCell<i32> = OnceCell::with_value(12);
+ let cell = CELL;
+ assert_eq!(cell.get(), Some(&12));
+ }
+
+ #[test]
fn once_cell_get_mut() {
let mut c = OnceCell::new();
assert!(c.get_mut().is_none());
@@ -131,6 +138,41 @@ mod unsync {
}
#[test]
+ fn lazy_force_mut() {
+ let called = Cell::new(0);
+ let mut x = Lazy::new(|| {
+ called.set(called.get() + 1);
+ 92
+ });
+ assert_eq!(called.get(), 0);
+ let v = Lazy::force_mut(&mut x);
+ assert_eq!(called.get(), 1);
+
+ *v /= 2;
+ assert_eq!(*x, 46);
+ assert_eq!(called.get(), 1);
+ }
+
+ #[test]
+ fn lazy_get_mut() {
+ let called = Cell::new(0);
+ let mut x: Lazy<u32, _> = Lazy::new(|| {
+ called.set(called.get() + 1);
+ 92
+ });
+
+ assert_eq!(called.get(), 0);
+ assert_eq!(*x, 92);
+
+ let mut_ref: &mut u32 = Lazy::get_mut(&mut x).unwrap();
+ assert_eq!(called.get(), 1);
+
+ *mut_ref /= 2;
+ assert_eq!(*x, 46);
+ assert_eq!(called.get(), 1);
+ }
+
+ #[test]
fn lazy_default() {
static CALLED: AtomicUsize = AtomicUsize::new(0);
@@ -186,6 +228,7 @@ mod unsync {
#[test]
#[should_panic(expected = "reentrant init")]
+ #[ignore = "Android: ignore for now. Need to compile these binaries separately."]
fn reentrant_init() {
let x: OnceCell<Box<i32>> = OnceCell::new();
let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
@@ -208,10 +251,16 @@ mod unsync {
}
}
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "critical-section"))]
mod sync {
use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
+ #[cfg(feature = "std")]
+ use std::sync::Barrier;
+
+ #[cfg(not(feature = "std"))]
+ use core::cell::Cell;
+
use crossbeam_utils::thread::scope;
use once_cell::sync::{Lazy, OnceCell};
@@ -232,6 +281,12 @@ mod sync {
}
#[test]
+ fn once_cell_with_value() {
+ static CELL: OnceCell<i32> = OnceCell::with_value(12);
+ assert_eq!(CELL.get(), Some(&12));
+ }
+
+ #[test]
fn once_cell_get_mut() {
let mut c = OnceCell::new();
assert!(c.get_mut().is_none());
@@ -308,6 +363,41 @@ mod sync {
assert_eq!(cell.get(), Some(&"hello".to_string()));
}
+ #[cfg(feature = "std")]
+ #[test]
+ fn wait() {
+ let cell: OnceCell<String> = OnceCell::new();
+ scope(|s| {
+ s.spawn(|_| cell.set("hello".to_string()));
+ let greeting = cell.wait();
+ assert_eq!(greeting, "hello")
+ })
+ .unwrap();
+ }
+
+ #[cfg(feature = "std")]
+ #[test]
+ fn get_or_init_stress() {
+ let n_threads = if cfg!(miri) { 30 } else { 1_000 };
+ let n_cells = if cfg!(miri) { 30 } else { 1_000 };
+ let cells: Vec<_> = std::iter::repeat_with(|| (Barrier::new(n_threads), OnceCell::new()))
+ .take(n_cells)
+ .collect();
+ scope(|s| {
+ for t in 0..n_threads {
+ let cells = &cells;
+ s.spawn(move |_| {
+ for (i, (b, s)) in cells.iter().enumerate() {
+ b.wait();
+ let j = if t % 2 == 0 { s.wait() } else { s.get_or_init(|| i) };
+ assert_eq!(*j, i);
+ }
+ });
+ }
+ })
+ .unwrap();
+ }
+
#[test]
fn from_impl() {
assert_eq!(OnceCell::from("value").get(), Some(&"value"));
@@ -350,6 +440,7 @@ mod sync {
#[test]
#[cfg_attr(miri, ignore)] // miri doesn't support processes
+ #[cfg(feature = "std")]
#[ignore = "Android: ignore for now. Need to compile these binaries separately."]
fn reentrant_init() {
let examples_dir = {
@@ -378,6 +469,20 @@ mod sync {
}
}
+ #[cfg(not(feature = "std"))]
+ #[test]
+ #[should_panic(expected = "reentrant init")]
+ fn reentrant_init() {
+ let x: OnceCell<Box<i32>> = OnceCell::new();
+ let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
+ x.get_or_init(|| {
+ let r = x.get_or_init(|| Box::new(92));
+ dangling_ref.set(Some(r));
+ Box::new(62)
+ });
+ eprintln!("use after free: {:?}", dangling_ref.get().unwrap());
+ }
+
#[test]
fn lazy_new() {
let called = AtomicUsize::new(0);
@@ -533,9 +638,8 @@ mod sync {
}
#[test]
- #[cfg_attr(miri, ignore)] // FIXME: deadlocks, likely caused by https://github.com/rust-lang/miri/issues/1388
fn once_cell_does_not_leak_partially_constructed_boxes() {
- let n_tries = 100;
+ let n_tries = if cfg!(miri) { 10 } else { 100 };
let n_readers = 10;
let n_writers = 3;
const MSG: &str = "Hello, World";
@@ -559,11 +663,9 @@ mod sync {
}
}
+ #[cfg(feature = "std")]
#[test]
- #[cfg_attr(miri, ignore)] // miri doesn't support Barrier
fn get_does_not_block() {
- use std::sync::Barrier;
-
let cell = OnceCell::new();
let barrier = Barrier::new(2);
scope(|scope| {
@@ -595,12 +697,11 @@ mod sync {
#[cfg(feature = "race")]
mod race {
+ #[cfg(feature = "std")]
+ use std::sync::Barrier;
use std::{
num::NonZeroUsize,
- sync::{
- atomic::{AtomicUsize, Ordering::SeqCst},
- Barrier,
- },
+ sync::atomic::{AtomicUsize, Ordering::SeqCst},
};
use crossbeam_utils::thread::scope;
@@ -652,6 +753,7 @@ mod race {
assert_eq!(cell.get(), Some(val1));
}
+ #[cfg(feature = "std")]
#[test]
fn once_non_zero_usize_first_wins() {
let val1 = NonZeroUsize::new(92).unwrap();
@@ -731,12 +833,16 @@ mod race {
#[cfg(all(feature = "race", feature = "alloc"))]
mod race_once_box {
+ #[cfg(feature = "std")]
+ use std::sync::Barrier;
use std::sync::{
atomic::{AtomicUsize, Ordering::SeqCst},
- Arc, Barrier,
+ Arc,
};
+ #[cfg(feature = "std")]
use crossbeam_utils::thread::scope;
+
use once_cell::race::OnceBox;
#[derive(Default)]
@@ -766,6 +872,7 @@ mod race_once_box {
}
}
+ #[cfg(feature = "std")]
#[test]
fn once_box_smoke_test() {
let heap = Heap::default();
@@ -820,6 +927,7 @@ mod race_once_box {
assert_eq!(heap.total(), 0);
}
+ #[cfg(feature = "std")]
#[test]
fn once_box_first_wins() {
let cell = OnceBox::new();
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-19 15:11:31 +0000