8019192: StringIndexOutOfBoundsException: in Class.getSimpleName()

Reviewed-by: jrose

src/share/classes/java/lang/invoke/MemberName.java

@@ -98,7 +98,9 @@ import java.util.Objects;
     public String getName() {
         if (name == null) {
             expandFromVM();
-            if (name == null)  return null;
+            if (name == null) {
+                return null;
+            }
         }
         return name;
     }
@@ -119,28 +121,39 @@ import java.util.Objects;
     public MethodType getMethodType() {
         if (type == null) {
             expandFromVM();
-            if (type == null)  return null;
+            if (type == null) {
+                return null;
             }
-        if (!isInvocable())
+        }
+        if (!isInvocable()) {
             throw newIllegalArgumentException("not invocable, no method type");
+        }
+
+        {
+            // Get a snapshot of type which doesn't get changed by racing threads.
+            final Object type = this.type;
             if (type instanceof MethodType) {
                 return (MethodType) type;
             }
+        }
+
+        // type is not a MethodType yet.  Convert it thread-safely.
+        synchronized (this) {
             if (type instanceof String) {
                 String sig = (String) type;
                 MethodType res = MethodType.fromMethodDescriptorString(sig, getClassLoader());
-            this.type = res;
-            return res;
-        }
-        if (type instanceof Object[]) {
+                type = res;
+            } else if (type instanceof Object[]) {
                 Object[] typeInfo = (Object[]) type;
                 Class<?>[] ptypes = (Class<?>[]) typeInfo[1];
                 Class<?> rtype = (Class<?>) typeInfo[0];
                 MethodType res = MethodType.methodType(rtype, ptypes);
-            this.type = res;
-            return res;
+                type = res;
             }
-        throw new InternalError("bad method type "+type);
+            // Make sure type is a MethodType for racing threads.
+            assert type instanceof MethodType : "bad method type " + type;
+        }
+        return (MethodType) type;
     }
 
     /** Return the actual type under which this method or constructor must be invoked.
@@ -173,21 +186,34 @@ import java.util.Objects;
     public Class<?> getFieldType() {
         if (type == null) {
             expandFromVM();
-            if (type == null)  return null;
+            if (type == null) {
+                return null;
             }
-        if (isInvocable())
+        }
+        if (isInvocable()) {
             throw newIllegalArgumentException("not a field or nested class, no simple type");
+        }
+
+        {
+            // Get a snapshot of type which doesn't get changed by racing threads.
+            final Object type = this.type;
             if (type instanceof Class<?>) {
                 return (Class<?>) type;
             }
+        }
+
+        // type is not a Class yet.  Convert it thread-safely.
+        synchronized (this) {
             if (type instanceof String) {
                 String sig = (String) type;
                 MethodType mtype = MethodType.fromMethodDescriptorString("()"+sig, getClassLoader());
                 Class<?> res = mtype.returnType();
-            this.type = res;
-            return res;
+                type = res;
             }
-        throw new InternalError("bad field type "+type);
+            // Make sure type is a Class for racing threads.
+            assert type instanceof Class<?> : "bad field type " + type;
+        }
+        return (Class<?>) type;
     }
 
     /** Utility method to produce either the method type or field type of this member. */
@@ -201,10 +227,10 @@ import java.util.Objects;
     public String getSignature() {
         if (type == null) {
             expandFromVM();
-            if (type == null)  return null;
+            if (type == null) {
+                return null;
+            }
         }
-        if (type instanceof String)
-            return (String) type;
         if (isInvocable())
             return BytecodeDescriptor.unparse(getMethodType());
         else
@@ -463,10 +489,17 @@ import java.util.Objects;
         //assert(referenceKindIsConsistent());  // do this after resolution
     }
 
+    /**
+     * Calls down to the VM to fill in the fields.  This method is
+     * synchronized to avoid racing calls.
+     */
     private void expandFromVM() {
-        if (!isResolved())  return;
-        if (type instanceof Object[])
-            type = null;  // don't saddle JVM w/ typeInfo
+        if (type != null) {
+            return;
+        }
+        if (!isResolved()) {
+            return;
+        }
         MethodHandleNatives.expand(this);
     }