add ThreadLocal to WasmStore to prevent sharing across threads

Author: bluejekyll

Makefile

@@ -82,6 +82,10 @@ mvn-test: target/native
 mvn-compile: target/native
 	PLATFORM=${PLATFORM} ARCH=${ARCH} mvn compile
 
+.PHONY: package
+package: build
+	PLATFORM=${PLATFORM} ARCH=${ARCH} mvn package
+
 .PHONY: cleanliness
 cleanliness:
 	cargo clean -p wasmtime-jni -p wasmtime-jni-exports -p math -p slices -p strings

src/main/java/net/bluejekyll/wasmtime/AbstractOpaquePtr.java

@@ -33,7 +33,7 @@ public void run() {
         }
     }
 
-    protected final long getPtr() {
+    protected long getPtr() {
         return this.ptr;
     }
 

src/main/java/net/bluejekyll/wasmtime/WasmStore.java

@@ -3,15 +3,51 @@
 import java.lang.reflect.Method;
 
 public class WasmStore extends AbstractOpaquePtr {
+    // Store is !Send and !Sync in Rust, we will enforce that with a ThreadLocal
+    // TODO: do we need stackable stores?
+    private static final ThreadLocal<Long> STORE = new ThreadLocal<Long>();
+
     WasmStore(long ptr) {
-        super(ptr, WasmStore::freeStore);
+        super(ptr, WasmStore::freeStoreChecked);
+        if (STORE.get() != null) {
+            throw new IllegalStateException("Previous STORE not cleared for this thread");
+        }
+
+        STORE.set(ptr);
     }
 
     private static native void freeStore(long ptr);
 
     private static native long newLinkerNtv(long store_ptr);
 
+    private static void verifyStore(long ptr) {
+        if (STORE.get() != ptr) {
+            throw new IllegalStateException(String.format("STORE expected %d got %d", STORE.get(), ptr));
+        }
+    }
+
+    @Override
+    public long getPtr() {
+        long ptr = super.getPtr();
+        verifyStore(ptr);
+
+        return ptr;
+    }
+
     public WasmLinker newLinker() {
+        if (STORE.get() == null) {
+            throw new IllegalStateException("STORE not available for this thread, did a new thread get started?");
+        }
+
         return new WasmLinker(WasmStore.newLinkerNtv(this.getPtr()));
     }
+
+    public static void freeStoreChecked(long ptr) {
+        if (STORE.get() != ptr) {
+            throw new IllegalStateException(String.format("STORE expected %d got %d", STORE.get(), ptr));
+        }
+
+        WasmStore.freeStore(ptr);
+        STORE.remove();
+    }
 }