Memory safety is the property of a program being free from a class of bugs that arise from incorrect access to memory, including use-after-free, buffer overflows, and data races. These bugs are notorious sources of crashes and security vulnerabilities in low-level code, and different languages take different routes to prevent them.
One common approach is automatic memory management. Languages with a garbage collector reclaim memory the program no longer uses, removing the need for manual free calls and the dangling-pointer bugs they cause. The tradeoff is a runtime that periodically reclaims memory, which carries performance and predictability costs.
Rust takes a different route, providing memory safety without a garbage collector. As the official Rust site states, “Rust’s rich type system and ownership model guarantee memory-safety and thread-safety — enabling you to eliminate many classes of bugs at compile-time.” The Rust book emphasizes that ownership “enables Rust to make memory safety guarantees without needing a garbage collector,” moving the checks to compile time rather than runtime.
At the other end of the spectrum, languages like C and C++ rely on manual memory management, giving programmers fine control but placing the burden of avoiding unsafe access on the developer. Memory safety, then, is less a single feature than a goal that languages pursue with sharply different mechanisms and tradeoffs.