feat(c-api) Redefine wasm_store_t.

`wasm_store_t` is now a proper struct (rather than an opaque type) of
kind:

```rs
struct wasm_store_t {
    inner: Store
}
```

The rest of the patch updates the code accordingly.

lib/c-api/src/wasm_c_api/externals/function.rs

@@ -4,9 +4,8 @@ use super::super::types::{wasm_functype_t, wasm_valkind_enum};
 use super::super::value::{wasm_val_inner, wasm_val_t};
 use std::convert::TryInto;
 use std::ffi::c_void;
-use std::ptr::NonNull;
 use std::sync::Arc;
-use wasmer::{Function, Instance, RuntimeError, Store, Val};
+use wasmer::{Function, Instance, RuntimeError, Val};
 
 #[allow(non_camel_case_types)]
 pub struct wasm_func_t {
@@ -31,13 +30,11 @@ pub type wasm_env_finalizer_t = unsafe extern "C" fn(c_void);
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_func_new(
-    store: Option<NonNull<wasm_store_t>>,
+    store: &wasm_store_t,
     ft: &wasm_functype_t,
     callback: wasm_func_callback_t,
 ) -> Option<Box<wasm_func_t>> {
     // TODO: handle null pointers?
-    let store_ptr = store?.cast::<Store>();
-    let store = store_ptr.as_ref();
     let func_sig = ft.sig();
     let num_rets = func_sig.results().len();
     let inner_callback = move |args: &[Val]| -> Result<Vec<Val>, RuntimeError> {
@@ -68,24 +65,23 @@ pub unsafe extern "C" fn wasm_func_new(
             .expect("Result conversion failed");
         Ok(processed_results)
     };
-    let f = Function::new(store, &func_sig, inner_callback);
+    let function = Function::new(&store.inner, &func_sig, inner_callback);
+
     Some(Box::new(wasm_func_t {
         instance: None,
-        inner: f,
+        inner: function,
     }))
 }
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_func_new_with_env(
-    store: Option<NonNull<wasm_store_t>>,
+    store: &wasm_store_t,
     ft: &wasm_functype_t,
     callback: wasm_func_callback_with_env_t,
     env: *mut c_void,
     finalizer: wasm_env_finalizer_t,
 ) -> Option<Box<wasm_func_t>> {
     // TODO: handle null pointers?
-    let store_ptr = store?.cast::<Store>();
-    let store = store_ptr.as_ref();
     let func_sig = ft.sig();
     let num_rets = func_sig.results().len();
     let inner_callback =
@@ -114,10 +110,11 @@ pub unsafe extern "C" fn wasm_func_new_with_env(
                 .expect("Result conversion failed");
             Ok(processed_results)
         };
-    let f = Function::new_with_env(store, &func_sig, env, inner_callback);
+    let function = Function::new_with_env(&store.inner, &func_sig, env, inner_callback);
+
     Some(Box::new(wasm_func_t {
         instance: None,
-        inner: f,
+        inner: function,
     }))
 }
 

lib/c-api/src/wasm_c_api/externals/global.rs

@@ -2,8 +2,7 @@ use super::super::store::wasm_store_t;
 use super::super::types::wasm_globaltype_t;
 use super::super::value::wasm_val_t;
 use std::convert::TryInto;
-use std::ptr::NonNull;
-use wasmer::{Global, Store, Val};
+use wasmer::{Global, Val};
 
 #[allow(non_camel_case_types)]
 pub struct wasm_global_t {
@@ -13,14 +12,13 @@ pub struct wasm_global_t {
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_global_new(
-    store_ptr: Option<NonNull<wasm_store_t>>,
+    store: &wasm_store_t,
     gt: &wasm_globaltype_t,
     val: &wasm_val_t,
 ) -> Option<Box<wasm_global_t>> {
     let gt = gt.as_globaltype();
     let wasm_val = val.try_into().ok()?;
-    let store_ptr: NonNull<Store> = store_ptr?.cast::<Store>();
-    let store = store_ptr.as_ref();
+    let store = &store.inner;
     let global = if gt.mutability.is_mutable() {
         Global::new_mut(store, wasm_val)
     } else {

lib/c-api/src/wasm_c_api/externals/memory.rs

@@ -1,8 +1,7 @@
 use super::super::store::wasm_store_t;
 use super::super::types::wasm_memorytype_t;
 use std::mem;
-use std::ptr::NonNull;
-use wasmer::{Memory, Pages, Store};
+use wasmer::{Memory, Pages};
 
 #[allow(non_camel_case_types)]
 pub struct wasm_memory_t {
@@ -12,14 +11,12 @@ pub struct wasm_memory_t {
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_memory_new(
-    store_ptr: Option<NonNull<wasm_store_t>>,
+    store: &wasm_store_t,
     mt: &wasm_memorytype_t,
 ) -> Option<Box<wasm_memory_t>> {
     let md = mt.as_memorytype().clone();
-    let store_ptr: NonNull<Store> = store_ptr?.cast::<Store>();
-    let store = store_ptr.as_ref();
+    let memory = c_try!(Memory::new(&store.inner, md));
 
-    let memory = c_try!(Memory::new(store, md));
     Some(Box::new(wasm_memory_t { inner: memory }))
 }
 

lib/c-api/src/wasm_c_api/externals/table.rs

@@ -1,7 +1,6 @@
 use super::super::store::wasm_store_t;
 use super::super::types::{wasm_ref_t, wasm_table_size_t, wasm_tabletype_t};
-use std::ptr::NonNull;
-use wasmer::{Store, Table};
+use wasmer::Table;
 
 #[allow(non_camel_case_types)]
 pub struct wasm_table_t {
@@ -11,17 +10,14 @@ pub struct wasm_table_t {
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_table_new(
-    store_ptr: Option<NonNull<wasm_store_t>>,
+    store: &wasm_store_t,
     tt: &wasm_tabletype_t,
     init: *const wasm_ref_t,
 ) -> Option<Box<wasm_table_t>> {
     let tt = tt.as_tabletype().clone();
-    let store_ptr: NonNull<Store> = store_ptr?.cast::<Store>();
-    let store = store_ptr.as_ref();
-
     let init_val = todo!("get val from init somehow");
+    let table = c_try!(Table::new(&store.inner, tt, init_val));
 
-    let table = c_try!(Table::new(store, tt, init_val));
     Some(Box::new(wasm_table_t { inner: table }))
 }
 

lib/c-api/src/wasm_c_api/instance.rs

@@ -4,7 +4,6 @@ use super::store::wasm_store_t;
 use super::trap::wasm_trap_t;
 use crate::ordered_resolver::OrderedResolver;
 use std::mem;
-use std::ptr::NonNull;
 use std::sync::Arc;
 use wasmer::{Extern, Instance};
 
@@ -52,7 +51,7 @@ unsafe fn argument_import_iter(
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_instance_new(
-    store: Option<NonNull<wasm_store_t>>,
+    _store: &wasm_store_t,
     module: &wasm_module_t,
     imports: *const *const wasm_extern_t,
     // own

lib/c-api/src/wasm_c_api/module.rs

@@ -7,7 +7,7 @@ use crate::error::update_last_error;
 use std::ptr::NonNull;
 use std::slice;
 use std::sync::Arc;
-use wasmer::{Module, Store};
+use wasmer::Module;
 
 #[allow(non_camel_case_types)]
 pub struct wasm_module_t {
@@ -16,14 +16,12 @@ pub struct wasm_module_t {
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_module_new(
-    store_ptr: Option<NonNull<wasm_store_t>>,
+    store: &wasm_store_t,
     bytes: &wasm_byte_vec_t,
 ) -> Option<Box<wasm_module_t>> {
     // TODO: review lifetime of byte slice
     let wasm_byte_slice: &[u8] = slice::from_raw_parts_mut(bytes.data, bytes.size);
-    let store_ptr: NonNull<Store> = store_ptr?.cast::<Store>();
-    let store = store_ptr.as_ref();
-    let module = c_try!(Module::from_binary(store, wasm_byte_slice));
+    let module = c_try!(Module::from_binary(&store.inner, wasm_byte_slice));
 
     Some(Box::new(wasm_module_t {
         inner: Arc::new(module),
@@ -35,20 +33,13 @@ pub unsafe extern "C" fn wasm_module_delete(_module: Option<Box<wasm_module_t>>)
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_module_validate(
-    store_ptr: Option<NonNull<wasm_store_t>>,
+    store: &wasm_store_t,
     bytes: &wasm_byte_vec_t,
 ) -> bool {
     // TODO: review lifetime of byte slice.
     let wasm_byte_slice: &[u8] = slice::from_raw_parts(bytes.data, bytes.size);
 
-    if store_ptr.is_none() {
-        return false;
-    }
-
-    let store_ptr = store_ptr.unwrap().cast::<Store>();
-    let store = store_ptr.as_ref();
-
-    if let Err(error) = Module::validate(store, wasm_byte_slice) {
+    if let Err(error) = Module::validate(&store.inner, wasm_byte_slice) {
         update_last_error(error);
 
         false
@@ -89,7 +80,7 @@ pub unsafe extern "C" fn wasm_module_imports(
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_module_deserialize(
-    store_ptr: Option<NonNull<wasm_store_t>>,
+    store: &wasm_store_t,
     bytes: *const wasm_byte_vec_t,
 ) -> Option<NonNull<wasm_module_t>> {
     // TODO: read config from store and use that to decide which compiler to use
@@ -101,9 +92,7 @@ pub unsafe extern "C" fn wasm_module_deserialize(
         (&*bytes).into_slice().unwrap()
     };
 
-    let store_ptr: NonNull<Store> = store_ptr?.cast::<Store>();
-    let store = store_ptr.as_ref();
-    let module = c_try!(Module::deserialize(store, byte_slice));
+    let module = c_try!(Module::deserialize(&store.inner, byte_slice));
 
     Some(NonNull::new_unchecked(Box::into_raw(Box::new(
         wasm_module_t {
@@ -117,7 +106,7 @@ pub unsafe extern "C" fn wasm_module_serialize(
     module: &wasm_module_t,
     out_ptr: &mut wasm_byte_vec_t,
 ) {
-    let mut byte_vec = match module.inner.serialize() {
+    let byte_vec = match module.inner.serialize() {
         Ok(byte_vec) => byte_vec,
         Err(_) => return,
     };

lib/c-api/src/wasm_c_api/store.rs

@@ -4,25 +4,20 @@ use wasmer::Store;
 
 /// Opaque wrapper around `Store`
 #[allow(non_camel_case_types)]
-pub struct wasm_store_t {}
+pub struct wasm_store_t {
+    pub(crate) inner: Store,
+}
 
 #[no_mangle]
 pub unsafe extern "C" fn wasm_store_new(
     wasm_engine_ptr: Option<NonNull<wasm_engine_t>>,
-) -> Option<NonNull<wasm_store_t>> {
+) -> Option<Box<wasm_store_t>> {
     let wasm_engine_ptr = wasm_engine_ptr?;
     let wasm_engine = wasm_engine_ptr.as_ref();
     let store = Store::new(&*wasm_engine.inner);
-    Some(NonNull::new_unchecked(
-        Box::into_raw(Box::new(store)) as *mut wasm_store_t
-    ))
+
+    Some(Box::new(wasm_store_t { inner: store }))
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn wasm_store_delete(wasm_store: Option<NonNull<wasm_store_t>>) {
-    if let Some(s_inner) = wasm_store {
-        // this should not leak memory:
-        // we should double check it to make sure though
-        let _: Box<Store> = Box::from_raw(s_inner.cast::<Store>().as_ptr());
-    }
-}
+pub unsafe extern "C" fn wasm_store_delete(_store: Option<Box<wasm_store_t>>) {}

lib/c-api/src/wasm_c_api/wasi/mod.rs

@@ -16,9 +16,8 @@ use crate::error::{update_last_error, CApiError};
 use std::convert::TryFrom;
 use std::ffi::CStr;
 use std::os::raw::c_char;
-use std::ptr::NonNull;
 use std::slice;
-use wasmer::{Extern, NamedResolver, Store};
+use wasmer::{Extern, NamedResolver};
 use wasmer_wasi::{
     generate_import_object_from_env, get_wasi_version, WasiEnv, WasiFile, WasiState,
     WasiStateBuilder, WasiVersion,
@@ -241,7 +240,7 @@ pub unsafe extern "C" fn wasi_get_wasi_version(module: &wasm_module_t) -> wasi_v
 /// Takes ownership of `wasi_env_t`.
 #[no_mangle]
 pub unsafe extern "C" fn wasi_get_imports(
-    store: Option<NonNull<wasm_store_t>>,
+    store: &wasm_store_t,
     module: &wasm_module_t,
     wasi_env: &wasi_env_t,
     imports: *mut *mut wasm_extern_t,
@@ -251,13 +250,12 @@ pub unsafe extern "C" fn wasi_get_imports(
 
 /// Takes ownership of `wasi_env_t`.
 unsafe fn wasi_get_imports_inner(
-    store: Option<NonNull<wasm_store_t>>,
+    store: &wasm_store_t,
     module: &wasm_module_t,
     wasi_env: &wasi_env_t,
     imports: *mut *mut wasm_extern_t,
 ) -> Option<()> {
-    let store_ptr = store?.cast::<Store>();
-    let store = store_ptr.as_ref();
+    let store = &store.inner;
 
     let version = c_try!(
         get_wasi_version(&module.inner, false).ok_or_else(|| CApiError {