Merge #27

27: Add MSRV of 1.63 r=bertptrs a=bertptrs

Fixes #26.

Co-authored-by: Bert Peters <bert@bertptrs.nl>

.github/workflows/ci.yml

@@ -15,6 +15,7 @@ jobs:
     strategy:
       matrix:
         rust:
+          - "1.63" # minimum stable rust version
           - stable
           - beta
           - nightly

CHANGELOG.md

@@ -6,6 +6,11 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Added
+
+- The minimum supported Rust version is now defined as 1.63. Previously it was undefined.
+- Wrappers for `std::sync` primitives can now be `const` constructed.
+
 ### Breaking
 
 - Update [`parking_lot`][parking_lot] dependency to `0.12`.

Cargo.toml

@@ -10,6 +10,7 @@ keywords = ["mutex", "rwlock", "once", "thread"]
 description = "Ensure deadlock-free mutexes by allocating in order, or else."
 readme = "README.md"
 repository = "https://github.com/bertptrs/tracing-mutex"
+rust-version = "1.63"
 
 [package.metadata.docs.rs]
 # Build docs for all features so the documentation is more complete

README.md

@@ -23,10 +23,12 @@ tree out of it, and panics if your dependencies would create a cycle. It provide
 existing synchronization primitives with an identical API, and should be a drop-in replacement.
 
 Inspired by [this blogpost][whileydave], which references a similar behaviour implemented by
-[Abseil][abseil-mutex] for their mutexes.
+[Abseil][abseil-mutex] for their mutexes. [This article goes into more depth on the exact
+implementation.][article]
 
 [whileydave]: https://whileydave.com/2020/12/19/dynamic-cycle-detection-for-lock-ordering/
 [abseil-mutex]: https://abseil.io/docs/cpp/guides/synchronization
+[article]: https://bertptrs.nl/2022/06/23/deadlock-free-mutexes-and-directed-acyclic-graphs.html
 
 ## Usage
 
@@ -59,6 +61,9 @@ performance penalty in your production environment, this library also offers deb
 when debug assertions are enabled, and to `Mutex` when they are not. Similar helper types are
 available for other synchronization primitives.
 
+The minimum supported Rust version is 1.63. Increasing this is not considered a breaking change, but
+will be avoided within semver-compatible releases if possible.
+
 ### Features
 
 - Dependency-tracking wrappers for all locking primitives

bors.toml

@@ -1,4 +1,5 @@
 status = [
+    'Rust project (1.63)',
     'Rust project (stable)',
     'Rust project (beta)',
     'Documentation build',

src/lib.rs

@@ -53,7 +53,6 @@ use std::marker::PhantomData;
 use std::mem::MaybeUninit;
 use std::ops::Deref;
 use std::ops::DerefMut;
-use std::ptr;
 use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering;
 use std::sync::Mutex;
@@ -271,9 +270,7 @@ impl Drop for LazyMutexId {
             // We have a valid mutex ID and need to drop it
 
             // Safety: we know that this pointer is valid because the initializer has successfully run.
-            let mutex_id = unsafe { ptr::read((*self.inner.get()).as_ptr()) };
-
-            drop(mutex_id);
+            unsafe { (*self.inner.get()).assume_init_drop() };
         }
     }
 }

src/stdsync.rs

@@ -42,7 +42,6 @@ pub mod tracing {
 
     use crate::BorrowedMutex;
     use crate::LazyMutexId;
-    use crate::MutexId;
 
     /// Wrapper for [`std::sync::Mutex`].
     ///
@@ -51,7 +50,7 @@ pub mod tracing {
     #[derive(Debug, Default)]
     pub struct Mutex<T> {
         inner: sync::Mutex<T>,
-        id: MutexId,
+        id: LazyMutexId,
     }
 
     /// Wrapper for [`std::sync::MutexGuard`].
@@ -89,10 +88,10 @@ pub mod tracing {
 
     impl<T> Mutex<T> {
         /// Create a new tracing mutex with the provided value.
-        pub fn new(t: T) -> Self {
+        pub const fn new(t: T) -> Self {
             Self {
                 inner: sync::Mutex::new(t),
-                id: MutexId::new(),
+                id: LazyMutexId::new(),
             }
         }
 
@@ -220,8 +219,8 @@ pub mod tracing {
 
     impl Condvar {
         /// Creates a new condition variable which is ready to be waited on and notified.
-        pub fn new() -> Self {
-            Default::default()
+        pub const fn new() -> Self {
+            Self(sync::Condvar::new())
         }
 
         /// Wrapper for [`std::sync::Condvar::wait`].
@@ -294,7 +293,7 @@ pub mod tracing {
     #[derive(Debug, Default)]
     pub struct RwLock<T> {
         inner: sync::RwLock<T>,
-        id: MutexId,
+        id: LazyMutexId,
     }
 
     /// Hybrid wrapper for both [`std::sync::RwLockReadGuard`] and [`std::sync::RwLockWriteGuard`].
@@ -312,10 +311,10 @@ pub mod tracing {
     pub type RwLockWriteGuard<'a, T> = TracingRwLockGuard<'a, sync::RwLockWriteGuard<'a, T>>;
 
     impl<T> RwLock<T> {
-        pub fn new(t: T) -> Self {
+        pub const fn new(t: T) -> Self {
             Self {
                 inner: sync::RwLock::new(t),
-                id: MutexId::new(),
+                id: LazyMutexId::new(),
             }
         }