1# Debugging WebAssembly
2
3The following steps describe a common way to debug a WebAssembly module in
4Wasmtime:
5
61. Compile your WebAssembly with debug info enabled, usually `-g`; for
7   example:
8
9    ```sh
10    clang foo.c -g -o foo.wasm
11    ```
12
132. Run Wasmtime with the debug info enabled; this is `-g` from the CLI and
14   `Config::debug_info(true)` in an embedding (e.g. see [debugging in a Rust
15   embedding](./examples-rust-debugging.md))
16
173. Use a supported debugger:
18
19    ```sh
20    lldb -- wasmtime run -D debug-info foo.wasm
21    ```
22    ```sh
23    gdb --args wasmtime run -D debug-info foo.wasm
24    ```
25
26If you run into trouble, the following discussions might help:
27
28- On MacOS with LLDB you may need to run: `settings set
29  plugin.jit-loader.gdb.enable on`
30  ([#1953](https://github.com/bytecodealliance/wasmtime/issues/1953))
31- With LLDB, call `__vmctx.set()` to set the current context before calling any
32  dereference operators
33  ([#1482](https://github.com/bytecodealliance/wasmtime/issues/1482)):
34  ```sh
35  (lldb) p __vmctx->set()
36  (lldb) p *foo
37  ```
38- The address of the start of instance memory can be found in `__vmctx->memory`
39- On Windows you may experience degraded WASM compilation throughput due to the
40  enablement of additional native heap checks when under the debugger by default.
41  You can set the environment variable `_NO_DEBUG_HEAP` to `1` to disable them.
42