Make wasmtime_component_instance_t non-opaque

Author: MangoPeachGrape

crates/c-api/include/wasmtime/component/instance.h

@@ -9,16 +9,19 @@
 extern "C" {
 #endif
 
-typedef struct wasmtime_component_instance_t wasmtime_component_instance_t;
-
-/**
- * \brief Deletes a #wasmtime_component_instance_t created by
- * #wasmtime_component_linker_instantiate
- *
- * \param instance the #wasmtime_component_instance_t to delete
- */
-WASM_API_EXTERN void
-wasmtime_component_instance_delete(wasmtime_component_instance_t *instance);
+/// \brief Representation of a instance in Wasmtime.
+///
+/// Instances are represented with a 64-bit identifying integer in Wasmtime.
+/// They do not have any destructor associated with them. Instances cannot
+/// interoperate between #wasmtime_store_t instances and if the wrong instance
+/// is passed to the wrong store then it may trigger an assertion to abort the
+/// process.
+typedef struct wasmtime_component_instance {
+  /// Internal identifier of what store this belongs to, never zero.
+  uint64_t store_id;
+  /// Internal index within the store.
+  size_t index;
+} wasmtime_component_instance_t;
 
 #ifdef __cplusplus
 } // extern "C"

crates/c-api/include/wasmtime/component/linker.h

@@ -67,7 +67,7 @@ WASM_API_EXTERN wasmtime_error_t *wasmtime_component_linker_instance(
 WASM_API_EXTERN wasmtime_error_t *wasmtime_component_linker_instantiate(
     const wasmtime_component_linker_t *linker, wasmtime_context_t *context,
     const wasmtime_component_t *component,
-    wasmtime_component_instance_t **instance_out);
+    wasmtime_component_instance_t *instance_out);
 
 /**
  * \brief Deletes a #wasmtime_component_linker_t created by

crates/c-api/src/component/instance.rs

@@ -1,11 +1,11 @@
 use std::ffi::{c_char, CStr};
 
 use anyhow::Context;
-use wasmtime::component::{Linker, LinkerInstance};
+use wasmtime::component::{Instance, Linker, LinkerInstance};
 
 use crate::{wasm_engine_t, wasmtime_error_t, WasmtimeStoreContextMut, WasmtimeStoreData};
 
-use super::{wasmtime_component_instance_t, wasmtime_component_t};
+use super::wasmtime_component_t;
 
 #[repr(transparent)]
 pub struct wasmtime_component_linker_t {
@@ -49,12 +49,10 @@ pub unsafe extern "C" fn wasmtime_component_linker_instantiate(
     linker: &wasmtime_component_linker_t,
     context: WasmtimeStoreContextMut<'_>,
     component: &wasmtime_component_t,
-    instance_out: &mut *mut wasmtime_component_instance_t,
+    instance_out: &mut Instance,
 ) -> Option<Box<wasmtime_error_t>> {
     let result = linker.linker.instantiate(context, &component.component);
-    crate::handle_result(result, |instance| {
-        *instance_out = Box::into_raw(Box::new(wasmtime_component_instance_t { instance }));
-    })
+    crate::handle_result(result, |instance| *instance_out = instance)
 }
 
 #[unsafe(no_mangle)]

crates/c-api/src/component/linker.rs

@@ -1,7 +1,5 @@
 mod component;
-mod instance;
 mod linker;
 
 pub use component::*;
-pub use instance::*;
 pub use linker::*;

crates/c-api/src/component/mod.rs

@@ -38,13 +38,10 @@ TEST(component, instantiate) {
 
   wasmtime_component_linker_instance_delete(linker_instance);
 
-  wasmtime_component_instance_t *instance = nullptr;
+  wasmtime_component_instance_t instance = {};
   error = wasmtime_component_linker_instantiate(linker, context, component,
                                                 &instance);
   EXPECT_EQ(error, nullptr);
-  EXPECT_NE(instance, nullptr);
-
-  wasmtime_component_instance_delete(instance);
 
   wasmtime_component_linker_delete(linker);