标准库

Rust comes with a standard library which helps establish a set of common types used by Rust libraries and programs. This way, two libraries can work together smoothly because they both use the same String type.

In fact, Rust contains several layers of the Standard Library: core, alloc and std.

• core includes the most basic types and functions that don’t depend on libc, allocator or even the presence of an operating system.
• alloc 包括需要全局堆分配器的类型，例如 Vec、Box 和 Arc。
• 嵌入式 Rust 应用通常只使用 core，偶尔会使用 alloc。