WebAssembly: How to Allocate Your Allocator

April 19, 2025 nullprogram.com/blog/2025/04/19/ An early, small hurdle diving into WebAssembly was allocating my allocator. On a server or desktop with virtual memory, the allocator asks the operating system to map fresh pages into its address space (sbrk, anonymous mmap, VirtualAlloc), which it then dynamically allocates to different purposes. In an embedded context, dynamic allocation memory is typically a fixed, static region chosen at link time. The WASM execution environment more resembles an embedded system, but both kinds of obtaining raw memory are viable and useful in different situations. For the purposes of this discussion, the actual allocator isn’t important. It could be a simple arena allocator, or a more general purpose buddy allocator. It could even be garbage collected with Boehm GC. Though WebAssembly’s linear memory is a poor fit for such a conservative garbage collector. In a compact address space starting at zero, and which doesn’t include code, memory addresses ... Read full article.