Reimplement in 100% safe code (#11)

.github/workflows/ci.yml

@@ -45,7 +45,7 @@ jobs:
       matrix:
         # When updating this, the reminder to update the minimum supported
         # Rust version in Cargo.toml.
-        rust: ['1.35']
+        rust: ['1.63']
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust

Cargo.toml

@@ -6,7 +6,7 @@ name = "easy-parallel"
 version = "3.3.0"
 authors = ["Stjepan Glavina <[email protected]>"]
 edition = "2018"
-rust-version = "1.35"
+rust-version = "1.63"
 description = "Run closures in parallel"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/easy-parallel"

src/lib.rs

@@ -57,12 +57,11 @@
 //! ```
 
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
+#![forbid(unsafe_code)]
 
 use std::fmt;
 use std::iter::{self, FromIterator};
-use std::mem;
 use std::panic;
-use std::process;
 use std::sync::mpsc;
 use std::thread;
 
@@ -256,58 +255,50 @@ impl<'a, T> Parallel<'a, T> {
         T: Send + 'a,
         C: FromIterator<T>,
     {
-        // Set up a guard that aborts on panic.
-        let guard = NoPanic;
+        // Set up a new thread scope.
+        thread::scope(|scope| {
+            // Join handles for spawned threads.
+            let mut handles = Vec::new();
 
-        // Join handles for spawned threads.
-        let mut handles = Vec::new();
+            // Channels to collect results from spawned threads.
+            let mut receivers = Vec::new();
 
-        // Channels to collect results from spawned threads.
-        let mut receivers = Vec::new();
+            for f in self.closures.into_iter() {
+                // Wrap into a closure that sends the result back.
+                let (sender, receiver) = mpsc::channel();
+                let f = move || sender.send(f()).unwrap();
 
-        // Spawn a thread for each closure after the first one.
-        for f in self.closures.into_iter() {
-            // Wrap into a closure that sends the result back.
-            let (sender, receiver) = mpsc::channel();
-            let f = move || sender.send(f()).unwrap();
-
-            // Erase the `'a` lifetime.
-            let f: Box<dyn FnOnce() + Send + 'a> = Box::new(f);
-            let f: Box<dyn FnOnce() + Send + 'static> = unsafe { mem::transmute(f) };
-
-            // Spawn a thread for the closure.
-            handles.push(thread::spawn(f));
-            receivers.push(receiver);
-        }
+                // Spawn it on the scope.
+                handles.push(scope.spawn(f));
+                receivers.push(receiver);
+            }
 
-        let mut last_err = None;
+            let mut last_err = None;
 
-        // Run the main closure on the main thread.
-        let res = panic::catch_unwind(panic::AssertUnwindSafe(f));
+            // Run the main closure on the main thread.
+            let res = panic::catch_unwind(panic::AssertUnwindSafe(f));
 
-        // Join threads and save the last panic if there was one.
-        for h in handles {
-            if let Err(err) = h.join() {
-                last_err = Some(err);
+            // Join threads and save the last panic if there was one.
+            for h in handles {
+                if let Err(err) = h.join() {
+                    last_err = Some(err);
+                }
             }
-        }
-
-        // Drop the guard because we may resume a panic now.
-        drop(guard);
 
-        // If a thread has panicked, resume the last collected panic.
-        if let Some(err) = last_err {
-            panic::resume_unwind(err);
-        }
+            // If a thread has panicked, resume the last collected panic.
+            if let Some(err) = last_err {
+                panic::resume_unwind(err);
+            }
 
-        // Collect the results from threads.
-        let results = receivers.into_iter().map(|r| r.recv().unwrap()).collect();
+            // Collect the results from threads.
+            let results = receivers.into_iter().map(|r| r.recv().unwrap()).collect();
 
-        // If the main closure panicked, resume its panic.
-        match res {
-            Ok(r) => (results, r),
-            Err(err) => panic::resume_unwind(err),
-        }
+            // If the main closure panicked, resume its panic.
+            match res {
+                Ok(r) => (results, r),
+                Err(err) => panic::resume_unwind(err),
+            }
+        })
     }
 }
 
@@ -324,14 +315,3 @@ impl<T> Default for Parallel<'_, T> {
         Self::new()
     }
 }
-
-/// Aborts the process if dropped while panicking.
-struct NoPanic;
-
-impl Drop for NoPanic {
-    fn drop(&mut self) {
-        if thread::panicking() {
-            process::abort();
-        }
-    }
-}