Version: 0.16 (unstable)

MASM Debug Output

Miden Assembly's debug.* instructions (debug.stack, debug.stack.<n>, debug.mem, debug.local.<a>.<b>, debug.adv_stack.<n> — see the assembly reference) print VM state to the client's standard output while a script runs. This is a lightweight alternative to interactive DAP debugging.

They only print when the client that executes the script is in debug mode — enable it with .in_debug_mode(DebugMode::Enabled) on the builder, or run the CLI with --debug (or MIDEN_DEBUG=true). Compilation is unaffected; the decorators are always retained in freshly compiled scripts. Output goes to the client's standard output (not tracing/RUST_LOG, not the node logs).

Example

Compile and execute a script containing debug.stack with a debug-mode client:

// Client built with `.in_debug_mode(DebugMode::Enabled)`.
let tx_script = client.code_builder().compile_tx_script(
    "
    begin
        push.1.2.3
        debug.stack.3
        drop drop drop
    end
    ",
)?;

client
    .execute_program(account_id, tx_script, AdviceInputs::default(), BTreeMap::new())
    .await?;

Executing it prints the top three stack elements to the client's standard output (the step count includes the transaction prologue that runs before the script):

Stack state in interval [0, 2] before step 2419:
├── 0: 3
├── 1: 2
├── 2: 1
└── (16 more items)

Under tests, pass --no-capture (cargo nextest, used by make test) or --nocapture (cargo test) to see the output.

Example​

Example