cranelift/docs/examples-debugging.md

Debugging WebAssembly

The following steps describe a common way to debug a WebAssembly module in Wasmtime:

1. Compile your WebAssembly with debug info enabled, usually -g; for example:

   clang foo.c -g -o foo.wasm
   

2. Run Wasmtime with the debug info enabled; this is -g from the CLI and Config::debug_info(true) in an embedding (e.g. see debugging in a Rust embedding)

3. Use a supported debugger:

   lldb -- wasmtime run -g foo.wasm
   

   gdb --args wasmtime run -g foo.wasm
   

If you run into trouble, the following discussions might help:

• On MacOS with LLDB you may need to run: settings set plugin.jit-loader.gdb.enable on (#1953)
• With LLDB, call __vmctx.set() to set the current context before calling any dereference operators (#1482):

  (lldb) p __vmctx->set()
  (lldb) p *foo
  

• The address of the start of instance memory can be found in __vmctx->memory