Bugzilla

A more concrete proposal:

(1) In a header file we have a macro "list" like this:

  _(GetProperty, js::GetProperty) \
  _(SetProperty, js::SetProperty, extra VMFunction args) \
  ...

In the header file we use the macro to define an enum:

  enum class VMFunctionIndex : uint32_t { GetProperty, SetProperty, ... }

(2) In the cpp file we have a list of signatures:

  using GetPropertyFn = bool (*)(JSContext*, HandleObject, MutableHandleValue);
  using SetPropertyFn = ...
  ...

This file also uses the macro in (1) to automatically generate:

static constexpr VMFunction vmFunctions[] = {
  FunctionInfo<GetPropertyFn>(js::GetProperty, ...),
  FunctionInfo<SetPropertyFn>(js::SetProperty, ...),
  ...
};

(3) We have the following function to do the lookup:

  const VMFunction& GetVMFunction(VMFunctionIndex index) { return vmFunctions[index]; }

----

To add a new VMFunction, you have to (1) add an entry to the macro in the header file (2) add a using statement in the cpp file. After that you can just use callVM(VMFunctionIndex::Foo).

When someone changes a function signature, they will get a compile error for FooFn in the cpp file and they can then fix all VMFunctionIndex::FooIndex uses.

A more concrete proposal:

(1) In a header file we have a macro "list" like this:
```
  _(GetProperty, js::GetProperty) \
  _(SetProperty, js::SetProperty, extra VMFunction args) \
  ...
```

In the header file we use the macro to define an enum:

  `enum class VMFunctionIndex : uint32_t { GetProperty, SetProperty, ... }`

(2) In the cpp file we have a list of signatures:
```
  using GetPropertyFn = bool (*)(JSContext*, HandleObject, MutableHandleValue);
  using SetPropertyFn = ...
  ...
```

This file also uses the macro in (1) to automatically generate:
```
static constexpr VMFunction vmFunctions[] = {
  FunctionInfo<GetPropertyFn>(js::GetProperty, ...),
  FunctionInfo<SetPropertyFn>(js::SetProperty, ...),
  ...
};
```

(3) We have the following function to do the lookup:

  `const VMFunction& GetVMFunction(VMFunctionIndex index) { return vmFunctions[index]; }`

----

To add a new VMFunction, you have to (1) add an entry to the macro in the header file (2) add a using statement in the cpp file. After that you can just use callVM(VMFunctionIndex::Foo).

When someone changes a function signature, they will get a compile error for FooFn in the cpp file and they can then fix all VMFunctionIndex::FooIndex uses.