alloc_arena.Arena

1/// `Arena` groups allocations under one caller-controlled lifetime and releases2/// them together. When allocation observation is disabled, `Arena` aliases3/// `std.heap.ArenaAllocator`. When observation is enabled through4/// `-Dobserve-allocations=true`, it aliases `ObservedArena`, which wraps a5/// standard arena with an observation identity. Both variants provide `init`,6/// `allocator`, `deinit`, `queryCapacity`, `reset`, and the `ResetMode` union.7/// Standard library details such as `std.heap.ArenaAllocator.State`, `promote`,8/// and concrete struct fields are not guaranteed when observation is active.9///10/// The owner enforces no fixed byte or node capacity cap of its own, drawing11/// fresh blocks on demand from a backing allocator. An `Allocator` handle12/// returned by `allocator` stores a pointer back to the arena, requiring the13/// caller to keep the arena owner at a stable memory address while using that14/// handle. The caller must keep the backing allocator state alive until the15/// arena and all allocated memory are torn down, but the small handle value16/// itself can be copied freely.17///18/// Calling `reset` or `deinit` ends the lifetime of all existing allocations at19/// once and invalidates every slice previously handed out. The arena does not20/// invoke destructors on individual objects before reclaiming storage, and21/// physical release of memory to the operating system depends on the backing22/// allocator.23///24/// The allocation vtable is thread-safe when the backing allocator is25/// thread-safe. In contrast, `reset` and `deinit` mutate internal state, and26/// `queryCapacity` reads shared state without synchronization, requiring27/// callers to exclude concurrent operations during those calls. When28/// observation is active, the allocation vtable remains thread-safe if both the29/// backing allocator and observation sinks support concurrent calls, but30/// observation callbacks require their own synchronization.31pub const Arena = if (observe.enabled)32    ObservedArena33else34    std.heap.ArenaAllocator;

1/// Exports the primary arena allocator, which groups multiple allocations under2/// a single caller-managed lifetime and supports resetting capacity for reuse.3/// At compile time, this alias resolves to ObservedArena when allocation4/// observation is enabled and to std.heap.ArenaAllocator when disabled.5pub const Arena = arena.Arena;