The standard allocators

Decided

D-0047, settled by the language’s author: part of spec §18. Older text cites it as 18.47.

Allocators::Global and Allocators::Temp, no Arena for now; memory tracking is opt-in. Global is malloc/free; Temp is a per-thread arena reset where the program chooses. The Allocator trait takes &mut self — an arena changes on every allocation — and its methods end in loc: SourceLocation = #location, which containers forward, so tracking reports name user code. Tracking is off in every build mode until [build] track_memory = true or --track-memory turns it on, and then reports leaks at exit, double and foreign frees, a free whose size or alignment differs from the allocation, and poisons Temp’s memory on reset so a stale read shows. The allocator types are in the prelude; larger stdlib areas are imported modules (§14)

Superseded in part by D-0091 (r81, 2026-10-27, by the user): Allocators::Temp is no longer for user code, since the compiler places memory (§14.6); Global, Temp and the Allocator trait stay in std, for writing containers. Memory tracking is unchanged.