[wasmtime-api] reduce examples complexity: hostref for store/engine (#489)

* reduce amount of store.clone()

* use HostRef Engine as ref / use Engine::default()

wasmtime-api/examples/gcd.rs

@@ -10,10 +10,10 @@ fn main() -> Result<()> {
 
     // Instantiate engine and store.
     let engine = HostRef::new(Engine::default());
-    let store = HostRef::new(Store::new(engine));
+    let store = HostRef::new(Store::new(&engine));
 
     // Load a module.
-    let module = HostRef::new(Module::new(store.clone(), &wasm)?);
+    let module = HostRef::new(Module::new(&store, &wasm)?);
 
     // Find index of the `gcd` export.
     let gcd_index = module
@@ -26,7 +26,7 @@ fn main() -> Result<()> {
         .0;
 
     // Instantiate the module.
-    let instance = HostRef::new(Instance::new(store.clone(), module, &[])?);
+    let instance = HostRef::new(Instance::new(&store, &module, &[])?);
 
     // Invoke `gcd` export
     let gcd = instance.borrow().exports()[gcd_index]

wasmtime-api/examples/hello.rs

@@ -21,8 +21,8 @@ impl Callable for HelloCallback {
 fn main() -> Result<()> {
     // Initialize.
     println!("Initializing...");
-    let engine = HostRef::new(Engine::new(Config::default()));
-    let store = HostRef::new(Store::new(engine));
+    let engine = HostRef::new(Engine::default());
+    let store = HostRef::new(Store::new(&engine));
 
     // Load binary.
     println!("Loading binary...");
@@ -30,19 +30,18 @@ fn main() -> Result<()> {
 
     // Compile.
     println!("Compiling module...");
-    let module =
-        HostRef::new(Module::new(store.clone(), &binary).context("> Error compiling module!")?);
+    let module = HostRef::new(Module::new(&store, &binary).context("> Error compiling module!")?);
 
     // Create external print functions.
     println!("Creating callback...");
     let hello_type = FuncType::new(Box::new([]), Box::new([]));
-    let hello_func = HostRef::new(Func::new(store.clone(), hello_type, Rc::new(HelloCallback)));
+    let hello_func = HostRef::new(Func::new(&store, hello_type, Rc::new(HelloCallback)));
 
     // Instantiate.
     println!("Instantiating module...");
     let imports = vec![hello_func.into()];
     let instance = HostRef::new(
-        Instance::new(store.clone(), module, imports.as_slice())
+        Instance::new(&store, &module, imports.as_slice())
             .context("> Error instantiating module!")?,
     );
 

wasmtime-api/examples/memory.rs

@@ -64,8 +64,8 @@ macro_rules! call {
 fn main() -> Result<(), Error> {
     // Initialize.
     println!("Initializing...");
-    let engine = HostRef::new(Engine::new(Config::default()));
-    let store = HostRef::new(Store::new(engine));
+    let engine = HostRef::new(Engine::default());
+    let store = HostRef::new(Store::new(&engine));
 
     // Load binary.
     println!("Loading binary...");
@@ -73,14 +73,12 @@ fn main() -> Result<(), Error> {
 
     // Compile.
     println!("Compiling module...");
-    let module =
-        HostRef::new(Module::new(store.clone(), &binary).context("> Error compiling module!")?);
+    let module = HostRef::new(Module::new(&store, &binary).context("> Error compiling module!")?);
 
     // Instantiate.
     println!("Instantiating module...");
-    let instance = HostRef::new(
-        Instance::new(store.clone(), module, &[]).context("> Error instantiating module!")?,
-    );
+    let instance =
+        HostRef::new(Instance::new(&store, &module, &[]).context("> Error instantiating module!")?);
 
     // Extract export.
     println!("Extracting export...");
@@ -141,7 +139,7 @@ fn main() -> Result<(), Error> {
     // TODO(wasm+): Once Wasm allows multiple memories, turn this into import.
     println!("Creating stand-alone memory...");
     let memorytype = MemoryType::new(Limits::new(5, 5));
-    let mut memory2 = Memory::new(store.clone(), memorytype);
+    let mut memory2 = Memory::new(&store, memorytype);
     check!(memory2.size(), 5u32);
     check!(memory2.grow(1), false);
     check!(memory2.grow(0), true);

wasmtime-api/examples/multi.rs

@@ -24,8 +24,8 @@ impl Callable for Callback {
 fn main() -> Result<()> {
     // Initialize.
     println!("Initializing...");
-    let engine = HostRef::new(Engine::new(Config::default()));
-    let store = HostRef::new(Store::new(engine));
+    let engine = HostRef::new(Engine::default());
+    let store = HostRef::new(Store::new(&engine));
 
     // Load binary.
     println!("Loading binary...");
@@ -33,8 +33,7 @@ fn main() -> Result<()> {
 
     // Compile.
     println!("Compiling module...");
-    let module =
-        HostRef::new(Module::new(store.clone(), &binary).context("Error compiling module!")?);
+    let module = HostRef::new(Module::new(&store, &binary).context("Error compiling module!")?);
 
     // Create external print functions.
     println!("Creating callback...");
@@ -42,13 +41,13 @@ fn main() -> Result<()> {
         Box::new([ValType::I32, ValType::I64]),
         Box::new([ValType::I64, ValType::I32]),
     );
-    let callback_func = HostRef::new(Func::new(store.clone(), callback_type, Rc::new(Callback)));
+    let callback_func = HostRef::new(Func::new(&store, callback_type, Rc::new(Callback)));
 
     // Instantiate.
     println!("Instantiating module...");
     let imports = vec![callback_func.into()];
     let instance = HostRef::new(
-        Instance::new(store.clone(), module, imports.as_slice())
+        Instance::new(&store, &module, imports.as_slice())
             .context("Error instantiating module!")?,
     );