Method call_raw

crates/wasmtime/src/runtime/component/func.rs:427–535

Invokes the underlying wasm function, lowering arguments and lifting the result. The `lower` function and `lift` function provided here are what actually do the lowering and lifting. The `LowerParams` and `LowerReturn` types are what will be allocated on the stack for this function call. They should be appropriately sized for the lowering/lifting operation happening. # Safety The safety of this

(
        &self,
        mut store: StoreContextMut<'_, T>,
        lower: impl FnOnce(
            &mut LowerContext<'_, T>,
            InterfaceType,
            &mut MaybeUninit<LowerParams>,
    

    /// for the params/results that are going to be produced. Additionally
    /// these types must be representable with a sequence of `ValRaw` values.
    unsafe fn call_raw<T, Return, LowerParams, LowerReturn>(
        &self,
        mut store: StoreContextMut<'_, T>,
        lower: impl FnOnce(
            &mut LowerContext<'_, T>,
            InterfaceType,
            &mut MaybeUninit<LowerParams>,
        ) -> Result<()>,
        lift: impl FnOnce(&mut LiftContext<'_>, InterfaceType, &LowerReturn) -> Result<Return>,
    ) -> Result<(Return, ValRaw)>
    where
        LowerParams: Copy,
        LowerReturn: Copy,
    {
        let export = self.lifted_core_func(store.0);
        let (_options, _flags, _ty, raw_options) = self.abi_info(store.0);
        let instance = self.instance.runtime_instance(raw_options.instance);

        if !store.0.may_enter(instance)? {
            bail!(crate::Trap::CannotEnterComponent);
        }

        let async_type = self.abi_async(store.0);
        store.0.enter_guest_sync_call(None, async_type, instance)?;

        #[repr(C)]
        union Union<Params: Copy, Return: Copy> {
            params: Params,
            ret: Return,
        }

        let space = &mut MaybeUninit::<Union<LowerParams, LowerReturn>>::uninit();

        // Double-check the size/alignment of `space`, just in case.
        //
        // Note that this alone is not enough to guarantee the validity of the
        // `unsafe` block below, but it's definitely required. In any case LLVM
        // should be able to trivially see through these assertions and remove
        // them in release mode.
        let val_size = mem::size_of::<ValRaw>();
        let val_align = mem::align_of::<ValRaw>();
        assert!(mem::size_of_val(space) % val_size == 0);
        assert!(mem::size_of_val(map_maybe_uninit!(space.params)) % val_size == 0);
        assert!(mem::size_of_val(map_maybe_uninit!(space.ret)) % val_size == 0);
        assert!(mem::align_of_val(space) == val_align);
        assert!(mem::align_of_val(map_maybe_uninit!(space.params)) == val_align);
        assert!(mem::align_of_val(map_maybe_uninit!(space.ret)) == val_align);

        self.with_lower_context(store.as_context_mut(), |cx, ty| {
            lower(cx, ty, map_maybe_uninit!(space.params))
        })?;

        // SAFETY: We are providing the guarantee that all the inputs are valid.
        // The various pointers passed in for the function are all valid since
        // they're coming from our store, and the `params_and_results` should
        // have the correct layout for the core wasm function we're calling.
        // Note that this latter point relies on the correctness of this module
        // and `ComponentType` implementations, hence `ComponentType` being an