What makes the Rust language one of the best for writing fast, memory-safe applications? Rust’s memory safety features are baked into the language itself.

In Rust, behaviors that are not memory-safe are treated not as runtime errors but as compiler errors. Whole classes of problems, like use-after-free(해제된 메모리 접근) error, are syntactically wrong in Rust.

This doesn’t mean that code written in Rust is entirely bulletproof or infallible. Some runtime issues, line race conditions, are still the developer’s responsibility. But Rust does take many common opportunities for software exploits off the table.

Unlike memory-managed languages(C#, Java, or Python), Rust binaries can be highly compact, run at machine-native speed by default, and remain memory-safe.

Rust variables: Immutable by default

All variables are immutable by default – This might seem trivial, but it has the net effect of forcing the developer to be fully conscious of what values need to be mutable in a program, and when. The resulting code is easier to reason about because it tells you what can change and where.

Immutable-by-default is distinct from the concept of a constant.

• immutable variable: can be computed and then stored as immutable at runtime – that is, it can be computed, stored, and then not changed.
• constant: computable at compile time, before the program ever runs. Many kinds of values – user input, for example – cannot be stored as constants this way.

Ownership, borrowing, and references in Rust

Every value in Rust has an “Owner”, meaning that only one thing at a time, at any given point in the code, can have full read/write control over value. Ownership can be given away or “borrowed” temporarily, but this behavior is strictly tracked by Rust’s compiler. Any code that violates the ownership rules for a given object simply doesn’t compile.

Lifetimes in Rust

References to values in Rust don’t just have owners, but lifetimes – meaning a scope for which a given reference is valid. In most Rust code, lifetimes can be left implicit, since the compiler traces them. But lifetime can also be explicitly annotated for more complex use cases. Regardless, attempting to access or modify something outside of its lifetime, or after it’s “gone out of scope”, results in a compiler error.

Rust enforces lifetime rules before the code ever runs.

Rust’s memory safety has costs

The first and largest cost is the need to learn and use the language itself. One of the common criticisms of Rust is its initial learning curve, even for experienced programmers.

C, C++, and all the rest have a large and entrenched user base, plenty of existing code and so on. But Rust has been in existence for more than the decade, it’s gained tooling, documentation, and a user-community that makes it easier to get up and speed. Using Rust may require a period of retraining and retooling but users will rarely lack the resources or library support for a given task.