Add host env via trait with proc macro

examples/wasi.rs

@@ -51,9 +51,6 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let import_object = wasi_env.import_object(&module)?;
     let instance = Instance::new(&module, &import_object)?;
 
-    // WASI requires to explicitly set the memory for the `WasiEnv`
-    wasi_env.set_memory(instance.exports.get_memory("memory")?.clone());
-
     println!("Call WASI `_start` function...");
     // And we just call the `_start` function!
     let start = instance.exports.get_function("_start")?;

lib/api/src/externals/function.rs

@@ -11,8 +11,8 @@ use std::cmp::max;
 use std::fmt;
 use wasmer_vm::{
     raise_user_trap, resume_panic, wasmer_call_trampoline, Export, ExportFunction,
-    VMCallerCheckedAnyfunc, VMContext, VMDynamicFunctionContext, VMFunctionBody, VMFunctionKind,
-    VMTrampoline,
+    FunctionExtraData, VMCallerCheckedAnyfunc, VMContext, VMDynamicFunctionContext, VMFunctionBody,
+    VMFunctionKind, VMTrampoline,
 };
 
 /// A function defined in the Wasm module
@@ -85,7 +85,9 @@ impl Function {
         // The engine linker will replace the address with one pointing to a
         // generated dynamic trampoline.
         let address = std::ptr::null() as *const VMFunctionBody;
-        let vmctx = Box::into_raw(Box::new(dynamic_ctx)) as *mut VMContext;
+        let vmctx = FunctionExtraData {
+            host_env: Box::into_raw(Box::new(dynamic_ctx)) as *mut _,
+        };
 
         Self {
             store: store.clone(),
@@ -94,6 +96,7 @@ impl Function {
                 address,
                 kind: VMFunctionKind::Dynamic,
                 vmctx,
+                function_ptr: None,
                 signature: ty.clone(),
                 call_trampoline: None,
             },
@@ -105,12 +108,16 @@ impl Function {
     /// # Example
     ///
     /// ```
-    /// # use wasmer::{Function, FunctionType, Type, Store, Value};
+    /// # use wasmer::{Function, FunctionType, Type, Store, Value, WasmerEnv, Instance};
     /// # let store = Store::default();
     ///
     /// struct Env {
     ///   multiplier: i32,
     /// };
+    /// impl WasmerEnv for Env {
+    ///     fn finish(&mut self, _instance: &Instance) {}
+    ///     fn free(&mut self) {}
+    /// }
     /// let env = Env { multiplier: 2 };
     ///
     /// let signature = FunctionType::new(vec![Type::I32, Type::I32], vec![Type::I32]);
@@ -124,7 +131,7 @@ impl Function {
     pub fn new_with_env<F, Env>(store: &Store, ty: &FunctionType, env: Env, func: F) -> Self
     where
         F: Fn(&mut Env, &[Val]) -> Result<Vec<Val>, RuntimeError> + 'static,
-        Env: Sized + 'static,
+        Env: Sized + crate::WasmerEnv + 'static,
     {
         let dynamic_ctx = VMDynamicFunctionContext::from_context(VMDynamicFunctionWithEnv {
             env: RefCell::new(env),
@@ -135,7 +142,12 @@ impl Function {
         // The engine linker will replace the address with one pointing to a
         // generated dynamic trampoline.
         let address = std::ptr::null() as *const VMFunctionBody;
-        let vmctx = Box::into_raw(Box::new(dynamic_ctx)) as *mut VMContext;
+        let vmctx = FunctionExtraData {
+            host_env: Box::into_raw(Box::new(dynamic_ctx)) as *mut _,
+        };
+        // TODO: look into removing transmute by changing API type signatures
+        let function_ptr = Some(unsafe { std::mem::transmute::<fn(_, _), fn(_, _)>(Env::finish) });
+        //dbg!(function_ptr);
 
         Self {
             store: store.clone(),
@@ -144,6 +156,7 @@ impl Function {
                 address,
                 kind: VMFunctionKind::Dynamic,
                 vmctx,
+                function_ptr,
                 signature: ty.clone(),
                 call_trampoline: None,
             },
@@ -176,7 +189,9 @@ impl Function {
     {
         let function = inner::Function::<Args, Rets>::new(func);
         let address = function.address() as *const VMFunctionBody;
-        let vmctx = std::ptr::null_mut() as *mut _ as *mut VMContext;
+        let vmctx = FunctionExtraData {
+            host_env: std::ptr::null_mut() as *mut _,
+        };
         let signature = function.ty();
 
         Self {
@@ -186,6 +201,9 @@ impl Function {
                 address,
                 vmctx,
                 signature,
+                // TODO: figure out what's going on in this function: it takes an `Env`
+                // param but also marks itself as not having an env
+                function_ptr: None,
                 kind: VMFunctionKind::Static,
                 call_trampoline: None,
             },
@@ -200,12 +218,16 @@ impl Function {
     /// # Example
     ///
     /// ```
-    /// # use wasmer::{Store, Function};
+    /// # use wasmer::{Store, Function, WasmerEnv, Instance};
     /// # let store = Store::default();
     ///
     /// struct Env {
     ///   multiplier: i32,
     /// };
+    /// impl WasmerEnv for Env {
+    ///     fn finish(&mut self, _instance: &Instance) {}
+    ///     fn free(&mut self) {}
+    /// }
     /// let env = Env { multiplier: 2 };
     ///
     /// fn sum_and_multiply(env: &mut Env, a: i32, b: i32) -> i32 {
@@ -219,7 +241,7 @@ impl Function {
         F: HostFunction<Args, Rets, WithEnv, Env>,
         Args: WasmTypeList,
         Rets: WasmTypeList,
-        Env: Sized + 'static,
+        Env: Sized + crate::WasmerEnv + 'static,
     {
         let function = inner::Function::<Args, Rets>::new(func);
         let address = function.address();
@@ -230,7 +252,12 @@ impl Function {
         // In the case of Host-defined functions `VMContext` is whatever environment
         // the user want to attach to the function.
         let box_env = Box::new(env);
-        let vmctx = Box::into_raw(box_env) as *mut _ as *mut VMContext;
+        let vmctx = FunctionExtraData {
+            host_env: Box::into_raw(box_env) as *mut _,
+        };
+        // TODO: look into removing transmute by changing API type signatures
+        let function_ptr = Some(unsafe { std::mem::transmute::<fn(_, _), fn(_, _)>(Env::finish) });
+        //dbg!(function_ptr as usize);
         let signature = function.ty();
 
         Self {
@@ -240,6 +267,7 @@ impl Function {
                 address,
                 kind: VMFunctionKind::Static,
                 vmctx,
+                function_ptr,
                 signature,
                 call_trampoline: None,
             },
@@ -365,7 +393,7 @@ impl Function {
             Self {
                 store: store.clone(),
                 definition: FunctionDefinition::Host(HostFunctionDefinition {
-                    has_env: !wasmer_export.vmctx.is_null(),
+                    has_env: !unsafe { wasmer_export.vmctx.host_env.is_null() },
                 }),
                 exported: wasmer_export,
             }

lib/api/src/instance.rs

@@ -85,11 +85,19 @@ impl Instance {
             })
             .collect::<Exports>();
 
-        Ok(Self {
+        let instance = Self {
             handle,
             module: module.clone(),
             exports,
-        })
+        };
+
+        unsafe {
+            instance
+                .handle
+                .initialize_host_envs(&instance as *const _ as *const _);
+        }
+
+        Ok(instance)
     }
 
     /// Gets the [`Module`] associated with this instance.

lib/api/src/lib.rs

@@ -118,3 +118,26 @@ pub use wasmer_engine_native::{Native, NativeArtifact, NativeEngine};
 
 /// Version number of this crate.
 pub const VERSION: &str = env!("CARGO_PKG_VERSION");
+
+// --------------------------------------------------------------
+// TODO: put this in a proper location, just prototyping for now:
+// TODO: rename everything, all names are throw-away names
+
+/// Prototype trait for finishing envs.
+pub trait WasmerEnv {
+    /// The function that Wasmer will call on your type to let it finish
+    /// instantiating.
+    fn finish(&mut self, instance: &Instance);
+
+    /// Frees memory written to `self` so it can be dropped without any memory leaks.
+    fn free(&mut self);
+}
+
+impl<T: WasmerEnv> WasmerEnv for &'static mut T {
+    fn finish(&mut self, instance: &Instance) {
+        (*self).finish(instance)
+    }
+    fn free(&mut self) {
+        (*self).free()
+    }
+}

lib/api/src/native.rs

@@ -17,7 +17,8 @@ use crate::{FromToNativeWasmType, Function, FunctionType, RuntimeError, Store, W
 use std::panic::{catch_unwind, AssertUnwindSafe};
 use wasmer_types::NativeWasmType;
 use wasmer_vm::{
-    ExportFunction, VMContext, VMDynamicFunctionContext, VMFunctionBody, VMFunctionKind,
+    ExportFunction, FunctionExtraData, VMContext, VMDynamicFunctionContext, VMFunctionBody,
+    VMFunctionKind,
 };
 
 /// A WebAssembly function that can be called natively
@@ -26,7 +27,7 @@ pub struct NativeFunc<'a, Args = (), Rets = ()> {
     definition: FunctionDefinition,
     store: Store,
     address: *const VMFunctionBody,
-    vmctx: *mut VMContext,
+    vmctx: FunctionExtraData,
     arg_kind: VMFunctionKind,
     // exported: ExportFunction,
     _phantom: PhantomData<(&'a (), Args, Rets)>,
@@ -42,7 +43,7 @@ where
     pub(crate) fn new(
         store: Store,
         address: *const VMFunctionBody,
-        vmctx: *mut VMContext,
+        vmctx: FunctionExtraData,
         arg_kind: VMFunctionKind,
         definition: FunctionDefinition,
     ) -> Self {
@@ -68,6 +69,8 @@ where
             address: other.address,
             vmctx: other.vmctx,
             signature,
+            // TODO:
+            function_ptr: None,
             kind: other.arg_kind,
             call_trampoline: None,
         }
@@ -88,6 +91,8 @@ where
                 address: other.address,
                 vmctx: other.vmctx,
                 signature,
+                // TODO:
+                function_ptr: None,
                 kind: other.arg_kind,
                 call_trampoline: None,
             },
@@ -165,7 +170,7 @@ macro_rules! impl_native_traits {
                         match self.arg_kind {
                             VMFunctionKind::Static => {
                                 let results = catch_unwind(AssertUnwindSafe(|| unsafe {
-                                    let f = std::mem::transmute::<_, unsafe extern "C" fn( *mut VMContext, $( $x, )*) -> Rets::CStruct>(self.address);
+                                    let f = std::mem::transmute::<_, unsafe extern "C" fn( FunctionExtraData, $( $x, )*) -> Rets::CStruct>(self.address);
                                     // We always pass the vmctx
                                     f( self.vmctx, $( $x, )* )
                                 })).map_err(|e| RuntimeError::new(format!("{:?}", e)))?;
@@ -175,12 +180,16 @@ macro_rules! impl_native_traits {
                                 let params_list = [ $( $x.to_native().to_value() ),* ];
                                 let results = if !has_env {
                                     type VMContextWithoutEnv = VMDynamicFunctionContext<VMDynamicFunctionWithoutEnv>;
-                                    let ctx = self.vmctx as *mut VMContextWithoutEnv;
-                                    unsafe { (*ctx).ctx.call(&params_list)? }
+                                    unsafe {
+                                        let ctx = self.vmctx.host_env as *mut VMContextWithoutEnv;
+                                        (*ctx).ctx.call(&params_list)?
+                                    }
                                 } else {
                                     type VMContextWithEnv = VMDynamicFunctionContext<VMDynamicFunctionWithEnv<std::ffi::c_void>>;
-                                    let ctx = self.vmctx as *mut VMContextWithEnv;
-                                    unsafe { (*ctx).ctx.call(&params_list)? }
+                                    unsafe {
+                                        let ctx = self.vmctx.host_env as *mut VMContextWithEnv;
+                                        (*ctx).ctx.call(&params_list)?
+                                    }
                                 };
                                 let mut rets_list_array = Rets::empty_array();
                                 let mut_rets = rets_list_array.as_mut() as *mut [i128] as *mut i128;

lib/api/src/types.rs

@@ -56,7 +56,9 @@ impl ValFuncRef for Val {
             Self::ExternRef(ExternRef::Null) => wasmer_vm::VMCallerCheckedAnyfunc {
                 func_ptr: ptr::null(),
                 type_index: wasmer_vm::VMSharedSignatureIndex::default(),
-                vmctx: ptr::null_mut(),
+                vmctx: wasmer_vm::FunctionExtraData {
+                    host_env: ptr::null_mut(),
+                },
             },
             Self::FuncRef(f) => f.checked_anyfunc(),
             _ => return Err(RuntimeError::new("val is not funcref")),
@@ -74,6 +76,9 @@ impl ValFuncRef for Val {
         let export = wasmer_vm::ExportFunction {
             address: item.func_ptr,
             signature,
+            // TODO:
+            // figure out if we ever need a value here: need testing with complicated import patterns
+            function_ptr: None,
             // All functions in tables are already Static (as dynamic functions
             // are converted to use the trampolines with static signatures).
             kind: wasmer_vm::VMFunctionKind::Static,

lib/api/tests/externals.rs

@@ -210,6 +210,11 @@ fn function_new_env() -> Result<()> {
     let store = Store::default();
     #[derive(Clone)]
     struct MyEnv {};
+    impl WasmerEnv for MyEnv {
+        fn finish(&mut self, _instance: &Instance) {}
+        fn free(&mut self) {}
+    }
+
     let my_env = MyEnv {};
     let function = Function::new_native_with_env(&store, my_env.clone(), |_env: &mut MyEnv| {});
     assert_eq!(function.ty().clone(), FunctionType::new(vec![], vec![]));
@@ -273,6 +278,10 @@ fn function_new_dynamic_env() -> Result<()> {
     #[derive(Clone)]
     struct MyEnv {};
     let my_env = MyEnv {};
+    impl WasmerEnv for MyEnv {
+        fn finish(&mut self, _instance: &Instance) {}
+        fn free(&mut self) {}
+    }
 
     let function_type = FunctionType::new(vec![], vec![]);
     let function = Function::new_with_env(

lib/c-api/src/deprecated/import/mod.rs

@@ -639,6 +639,11 @@ pub(crate) struct LegacyEnv {
     pub(crate) instance_ptr: Option<NonNull<CAPIInstance>>,
 }
 
+impl wasmer::WasmerEnv for LegacyEnv {
+    fn finish(&mut self, _instance: &wasmer::Instance) {}
+    fn free(&mut self) {}
+}
+
 impl LegacyEnv {
     pub(crate) fn ctx_ptr(&self) -> *mut CAPIInstance {
         self.instance_ptr

lib/c-api/src/deprecated/import/wasi.rs

@@ -4,7 +4,7 @@ use libc::c_uchar;
 use std::path::PathBuf;
 use std::ptr;
 use std::str;
-use wasmer::{Memory, MemoryType, NamedResolver};
+use wasmer::NamedResolver;
 use wasmer_wasi as wasi;
 
 #[derive(Debug, PartialEq)]
@@ -213,11 +213,6 @@ pub unsafe extern "C" fn wasmer_wasi_generate_default_import_object() -> *mut wa
     let mut wasi_state_builder = wasi::WasiState::new("wasmer-wasi-default-program-name");
     let wasi_state = wasi_state_builder.build().unwrap();
     let mut wasi_env = wasi::WasiEnv::new(wasi_state);
-    // this API will now leak a `Memory`
-    let memory_type = MemoryType::new(0, None, false);
-    let memory = Memory::new(store, memory_type).expect("create memory");
-    wasi_env.set_memory(memory);
-    // TODO(mark): review lifetime of `Memory` here
     let import_object_inner: Box<dyn NamedResolver> = Box::new(
         wasi::generate_import_object_from_env(store, wasi_env, wasi::WasiVersion::Latest),
     );