Debugging

Debugging with GDB

To debug a WebAssembly module using GDB, ensure that your module is compiled with debugging information (e.g., using the -g flag during compilation). Additionally, Wasmtime itself must be compiled in debug mode (i.e., without the --release flag) to enable effective debugging of both the runtime and the module. This allows GDB to access symbol information from both your program and Wasmtime.

Note: Current limitations in GDB support for WebAssembly include lack of instruction-level inspection. Commands like layout split and si (step instruction) may break the terminal. It’s recommended to use layout src for source-level debugging.

Running GDB with Wasmtime

Use the following command to start GDB with Wasmtime:

gdb --args ../wasmtime/target/debug/wasmtime run -D debug-info -O opt-level=0 malloc-test.wasm

Explanation of arguments:

gdb --args: Passes arguments to the program through GDB.
../wasmtime/target/debug/wasmtime run: Runs your WebAssembly module using the Wasmtime binary.
-D debug-info: Enables Wasmtime’s debug information support.
-O opt-level=0: Disables optimizations for easier debugging.

Example Debugging Session

Start GDB
Launch GDB with Wasmtime and your WebAssembly module:

gdb --args ../wasmtime/target/debug/wasmtime run -D debug-info -O opt-level=0 malloc-test.wasm

Set Breakpoints
In the GDB prompt, set breakpoints as needed:
```
(gdb) break main
```
Run the Program
Start execution:
```
(gdb) run
```
Inspect and Debug
Use GDB commands to step through and inspect your code:
```
(gdb) next
(gdb) print p
(gdb) continue
```

Additional Resources

Other Debugging Techniques

Coming soon