Memory Layout

When C developers first look at Rust types, the obvious move is to find familiar mappings: uint8_t to u8, int32_t to i32, size_t to usize, struct to struct.

That is a good starting point, but similar names are not enough.

In C, basic types, struct layout, alignment, and ABI affect file formats, network packets, register maps, dynamic library interfaces, and cross-language calls. Rust also cares about these issues, but its defaults have a different goal: Rust types first serve internal safety and optimization. If a type has to match C or a binary layout, that boundary must be made explicit.