Expose Engine::clone to c-api (#8907)

crates/c-api/README.md

@@ -8,7 +8,7 @@ For more information you can find the documentation for this library
 To use Wasmtime from a C or C++ project, you can use Cargo to build the Wasmtime C bindings. From the root of the Wasmtime repository, run the following command:
 
 ```
-cargo build --release wasmtime-c-api
+cargo build --release -p wasmtime-c-api
 ```
 
 This will create static and dynamic libraries called `libwasmtime` in the `target/release` directory.

crates/c-api/include/wasmtime/engine.h

@@ -13,6 +13,14 @@
 extern "C" {
 #endif
 
+/**
+ * \brief Create a new reference to the same underlying engine.
+ *
+ * This function clones the reference-counted pointer to the internal object,
+ * and must be freed using #wasm_engine_delete.
+ */
+WASM_API_EXTERN wasm_engine_t *wasmtime_engine_clone(wasm_engine_t *engine);
+
 /**
  * \brief Increments the engine-local epoch variable.
  *

crates/c-api/src/engine.rs

@@ -29,12 +29,20 @@ pub extern "C" fn wasm_engine_new() -> Box<wasm_engine_t> {
 
 #[no_mangle]
 pub extern "C" fn wasm_engine_new_with_config(c: Box<wasm_config_t>) -> Box<wasm_engine_t> {
+    #[cfg(feature = "logging")]
+    drop(env_logger::try_init());
+
     let config = c.config;
     Box::new(wasm_engine_t {
         engine: Engine::new(&config).unwrap(),
     })
 }
 
+#[no_mangle]
+pub extern "C" fn wasmtime_engine_clone(engine: &wasm_engine_t) -> Box<wasm_engine_t> {
+    Box::new(engine.clone())
+}
+
 #[no_mangle]
 pub extern "C" fn wasmtime_engine_increment_epoch(engine: &wasm_engine_t) {
     engine.engine.increment_epoch();