Trait Tracer

pub trait Tracer {
    // Provided methods
    fn before_instruction<OP: OpcodeType, S: GlobalStateInterface>(
        &mut self,
        state: &mut S,
    ) { ... }
    fn after_instruction<OP: OpcodeType, S: GlobalStateInterface>(
        &mut self,
        state: &mut S,
    ) -> ShouldStop { ... }
    fn on_extra_prover_cycles(&mut self, _stats: CycleStats) { ... }
}

EraVM instruction tracer.

Self::before_instruction() is called just before the actual instruction is executed. If the instruction is skipped, before_instruction will be called with Nop. Self::after_instruction() is called once the instruction is executed and the program counter has advanced.

Examples

Here FarCallCounter counts the number of far calls.

struct FarCallCounter(usize);

impl Tracer for FarCallCounter {
    fn before_instruction<OP: OpcodeType, S: GlobalStateInterface>(&mut self, state: &mut S) {
        match OP::VALUE {
            Opcode::FarCall(_) => self.0 += 1,
            _ => {}
        }
    }
}

Provided Methods

fn before_instruction<OP: OpcodeType, S: GlobalStateInterface>( &mut self, state: &mut S, )

This method is executed before an instruction handler.

The default implementation does nothing.

fn after_instruction<OP: OpcodeType, S: GlobalStateInterface>( &mut self, state: &mut S, ) -> ShouldStop

This method is executed after an instruction handler.

The return value indicates whether the VM should continue or stop execution. The tracer’s return value takes precedence over the VM but only if it is at least as severe. For example, if the VM wants to stop and the tracer wants to suspend, the VM will still stop.

The default implementation does nothing.

fn on_extra_prover_cycles(&mut self, _stats: CycleStats)

Provides cycle statistics for “complex” instructions from the prover perspective (mostly precompile calls).

The default implementation does nothing.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl Tracer for ()

No-op tracer implementation.

impl<A: Tracer, B: Tracer> Tracer for (A, B)

fn before_instruction<OP: OpcodeType, S: GlobalStateInterface>( &mut self, state: &mut S, )

fn after_instruction<OP: OpcodeType, S: GlobalStateInterface>( &mut self, state: &mut S, ) -> ShouldStop

fn on_extra_prover_cycles(&mut self, stats: CycleStats)

Implementors