Custom Allocator in Rust

Swapping What Backs Every Box and Vec

Rust routes global allocation through GlobalAlloc. Discord and others plug in jemalloc or mimalloc for fleet wins; embedded targets sometimes ship a bump allocator with no individual free. Your exercise implements the trait the standard library expects.

rustCopy
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• Layout carries size and align; both must be honored on return
• alloc may return null; callers handle OOM
• dealloc receives the same layout passed to alloc
• Thread-safe implementations are required for #[global_allocator]

Bump Pointer Mechanics

Align an offset with (offset + align - 1) & !(align - 1), bump past the allocation, never free until reset. Zero-sized layouts are valid edge cases.

For this exercise, you will implement a GlobalAlloc bump allocator on a fixed byte array. This task asks you to pass Layout through correctly, because misaligned returns corrupt Vec growth and produce impossible-to-debug segfaults deep inside std.

Keep the relevant man page, ABI doc, or Rust reference chapter open while you work. When your output disagrees with the reference implementation on the same machine, the mismatch is usually an alignment rule, an off-by-one terminator, or a register slot you misread in GDB.