The symbol was introduced in LLD 15.0.7, as a way to know how much memory can be allocated: 1095870e8c https://github.com/WebAssembly/wasi-libc/pull/377
1095870e8c
* Update wasi-libc to a00bf321eeeca836ee2a0d2d25aeb8524107b8cc It includes a port of emscripten's allocator that performs performs much better than the old one. Most importantly, it includes the prerequisites to later add support for POSIX threads.