Module wasm::wasm_rt

freestanding wasm32 runtime.

A wasm32-unknown-unknown build is linked with -nostdlib (see std/wasm/dom.h's header comment for the full toolchain invocation) — there is no libc, so the libc functions std's own sources call (malloc & co., the mem*/str* family, strtod/strtoll, qsort) and the compiler-rt builtins LLVM emits calls to (__multi3 & co. for 128-bit arithmetic) have no definition unless something in the module provides one. This file is that something, so a module needs no host imports beyond the ones its own code (and std/wasm/dom) declares.

The heap is a size-class allocator over the module's linear memory: blocks are powers of two (header included), freed blocks are reused by later allocations of the same class, and the memory grows (memory.grow) on demand from the linker's __heap_base — a long-running page can allocate and free indefinitely. Memory is never returned to the host.

Only meaningful for wasm32 freestanding targets — a hosted build (Cocoa/Win32/X11/bare-metal GUI, the RPC server, etc.) must keep using the real libc via std/mem.sc, not this file; including both in the same link would duplicate-symbol on malloc/free/etc.