How to Avoid Fighting Rust Borrow Checker
18 hours ago
- #Rust
- #Memory Safety
- #Borrow Checker
- Rust's ownership system forms a tree-shaped structure where each object has exactly one parent.
- Mutable borrows in Rust are exclusive, meaning no other borrows can coexist with a mutable borrow.
- Borrowing in Rust is contagious; borrowing a child indirectly borrows all its parents.
- Rust's borrow checker can reject some correct programs due to its conservative nature.
- Reference shapes in memory can be tree-shaped (simple) or involve sharing (complex).
- For shared immutable objects, use immutable borrows or reference counting (Rc/Arc).
- Shared mutable objects are borrow-check-unfriendly and require special solutions.
- Circular references in data structures complicate borrowing and require careful handling.
- Solutions for borrow-check-unfriendly cases include data-oriented design, ID/handles, and deferred mutation.
- Contagious borrowing can cause issues when borrowing a part of an object forces borrowing the whole object.
- Interior mutability (Cell, RefCell, Mutex) allows mutation through immutable references.
- Using IDs or handles instead of borrows can decouple object lifetimes from references.
- Deferring mutation by treating mutations as data (commands) can simplify borrowing.
- Circular references in programming are common but require weak references (Weak) to avoid memory leaks.
- Rust's mutable borrow exclusiveness is crucial for memory safety, especially with interior pointers.
- Reference counting (Rc/Arc) has performance costs due to atomic operations.
- Bump allocators provide fast allocation but cannot free individual objects.
- Unsafe Rust allows bypassing borrow checker but requires careful handling to avoid undefined behavior.
- Rust's Send and Sync traits ensure thread safety by controlling data sharing across threads.
- Async programming in Rust requires futures to be Send and 'static for thread safety.
- Temporary lifetime extension and reborrowing are subtle aspects of Rust's borrowing rules.
- Rust's trade-offs include memory safety and performance at the cost of flexibility and quick iteration.