Rust Memory Internals: How Alignment and Layout Shape Type Representation

In Rust, every value has a type that defines how its bits in memory are interpreted, with different types like u8 and i8 reading the same bit pattern as entirely different numbers. Hardware constraints require all values to begin on byte boundaries, and many types have stricter alignment needs tied to CPU word sizes, typically 8 bytes on 64-bit systems. Misaligned memory access forces the CPU to perform multiple reads and merge results, degrading performance and potentially causing concurrency issues. For primitive types, alignment matches their size, while compound types inherit the largest alignment of their fields. The Rust compiler uses these rules to compute a type's layout, determining how its components are arranged in memory.