Rust FFI and C Memory Model Integration: Shared Mutable State

Memory Safety Across the FFI Boundary

Rust provides strict memory safety guarantees via its ownership and borrowing system. When interfacing with C through the Foreign Function Interface (FFI), developers utilize unsafe blocks and repr(C) attributes to ensure layout compatibility and allow raw pointer dereferencing.

Concurrency and Data Race Uncertainty

While Rust prevents data races within its own memory model, the interaction between Rust's memory model and the memory models of foreign languages remains a complex integration point. Specifically, when shared mutable state is accessed concurrently across the FFI boundary, the compiler cannot enforce safety invariants on the C side of the interface.

Given that Rust's Sync and Send traits are not recognized by foreign compilers, there is uncertainty regarding the precise behavior of data races when a C thread modifies memory that Rust considers immutable or uniquely owned.

• How does the Rust memory model resolve conflicts when a foreign function violates Rust's aliasing rules?
• What are the formal guarantees regarding data races when shared state is manipulated across the FFI boundary?