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 the LLVM toolchain (compiled to include the experimental wasm32 target, see yurydelendik/wasmception). The path to the llvm binary directory has to be passed to the compilation script with the LLVM_ROOT environment variable.

Example invocation of the compilation script:

mkdir build
LLVM_ROOT=$HOME/ CFLAGS=-O2 ./compile build/main.wasm src/malloc.c src/test.c

Debug logging can be enabled with the preprocessor macro MALLOC_DEBUG. This also adds the function print_heap() which prints the current layout of the heap to the browser console.

In C these functions can be included with malloc.h, they have the exact same signature as in the C standard library.

The file test.c exports some test functions that you can call from JavaScript as instance.exports.test_malloc/free/...(...).