Macro for_each_visit_operator

macro_rules! for_each_visit_operator {
    ($m:ident) => { ... };
}

Used to implement the VisitOperator trait.

A helper macro to conveniently iterate over all opcodes recognized by this crate. This can be used to work with either the Operator enumeration or the VisitOperator trait if your use case uniformly handles all operators the same way.

It is also possible to specialize handling of operators depending on the Wasm proposal from which they are originating.

This is an “iterator macro” where this macro is invoked with the name of another macro, and then that macro is invoked with the list of all operators.

The list of specializable Wasm proposals is as follows:

• @mvp: Denoting a Wasm operator from the initial Wasm MVP version.
• @exceptions: Wasm exception-handling proposal
• @tail_call: Wasm tail-calls proposal
• @reference_types: Wasm reference-types proposal
• @sign_extension: Wasm sign-extension-ops proposal
• @saturating_float_to_int: Wasm non_trapping_float-to-int-conversions proposal
• @bulk_memory :Wasm bulk-memory proposal
• @threads: Wasm threads proposal
• @gc: Wasm gc proposal
• @stack_switching: Wasm stack-switching proposal
• @wide_arithmetic: Wasm wide-arithmetic proposal

Note that this macro does not iterate over the SIMD-related proposals. Those are provided in VisitSimdOperator and for_each_visit_simd_operator. This macro only handles non-SIMD related operators and so users wanting to handle the SIMD-class of operators need to use that trait/macro as well.

macro_rules! define_visit_operator {
    // The outer layer of repetition represents how all operators are
    // provided to the macro at the same time.
    //
    // The `$proposal` identifier indicates the Wasm proposals from which
    // the Wasm operator is originating.
    // For example to specialize the macro match arm for Wasm `gc` proposal
    // operators you could write `@gc` instead of `@$proposal:ident` to
    // only catch those operators.
    //
    // The `$op` name is bound to the `Operator` variant name. The
    // payload of the operator is optionally specified (the `$(...)?`
    // clause) since not all instructions have payloads. Within the payload
    // each argument is named and has its type specified.
    //
    // The `$visit` name is bound to the corresponding name in the
    // `VisitOperator` trait that this corresponds to.
    //
    // The `$ann` annotations give information about the operator's type (e.g. binary i32 or arity 2 -> 1).
    ($( @$proposal:ident $op:ident $({ $($arg:ident: $argty:ty),* })? => $visit:ident ($($ann:tt)*))*) => {
        $(
            fn $visit(&mut self $($(,$arg: $argty)*)?) {
                // do nothing for this example
            }
        )*
    }
}

pub struct VisitAndDoNothing;

impl<'a> wasmparser::VisitOperator<'a> for VisitAndDoNothing {
    type Output = ();

    wasmparser::for_each_visit_operator!(define_visit_operator);
}

If you only wanted to visit the initial base set of wasm instructions, for example, you could do:

macro_rules! visit_only_mvp {
    // delegate the macro invocation to sub-invocations of this macro to
    // deal with each instruction on a case-by-case basis.
    ($( @$proposal:ident $op:ident $({ $($arg:ident: $argty:ty),* })? => $visit:ident ($($ann:tt)*))*) => {
        $(
            visit_only_mvp!(visit_one @$proposal $op $({ $($arg: $argty),* })? => $visit);
        )*
    };

    // MVP instructions are defined manually, so do nothing.
    (visit_one @mvp $($rest:tt)*) => {};

    // Non-MVP instructions all return `false` here. The exact type depends
    // on `type Output` in the trait implementation below. You could change
    // it to `Result<()>` for example and return an error here too.
    (visit_one @$proposal:ident $op:ident $({ $($arg:ident: $argty:ty),* })? => $visit:ident) => {
        fn $visit(&mut self $($(,$arg: $argty)*)?) -> bool {
            false
        }
    }
}

pub struct VisitOnlyMvp;

impl<'a> wasmparser::VisitOperator<'a> for VisitOnlyMvp {
    type Output = bool;

    wasmparser::for_each_visit_operator!(visit_only_mvp);

    // manually define `visit_*` for all MVP operators here
}