A simple implementation of malloc/free for WebAssembly. The heap is a doubly linked lists, with blocks being merged or split if necessary/possible.
At the moment, realloc is not supported. malloc/calloc do not correctly align the memory.
Because the WebAssembly MVP does not support shrinking the linear memory, freed memory can not be released.
This requires llvm (compiled with the wasm32 target, see this gist), wabt and binaryen. The path to the llvm bin directory has to be adjusted in the compile script. wabt and binaryen must be accessible through the path.
mkdir build
CFLAGS=-O2 ./compile build/main.wasm src/mm.c src/main.c
Debugging information can be enabled with the preprocessor macro MM_DEBUG. This also adds the function print_heap() which prints the current layout of the
heap to the browser console.
Sadly Google Chrome currently has a bug which causes the tab to crash if WebAssembly.Memory#grow() is being called from WebAssembly. It works in Mozilla Firefox, I haven't tested it in other browsers.
The functions can be invoked in JavaScript as instance.exports.malloc()/calloc()/free().
In C these functions can be included with mm.h, they have the exact same signature as in the C standard library.