According to the JNI spec for NewWeakGlobalRef:

> Returns NULL if obj refers to null, or if obj was a weak global reference, or if the VM runs out of memory. If the VM runs out of memory, an OutOfMemoryError will be thrown.

The current behaviour is that `NewWeakGlobalRef(nullptr)` throws an OutOfMemoryError, which it should not.

```
 #include <stdio.h>
 #include <jni.h>
 #include "TestNull.h"

 JNIEXPORT void JNICALL Java_TestNull_testNull(JNIEnv *env, jclass a) {
     env->NewWeakGlobalRef(nullptr);
     env->ExceptionDescribe();
 }
```

```
class TestNull {
    static { System.loadLibrary("testNull"); }
    public static void main(String[] args) {
        testNull();
    }
    public static native void testNull();
}
```

```
java -Djava.library.path=. TestNull
Exception in thread "main" java.lang.OutOfMemoryError: C heap space
	at TestNull.testNull(Native Method)
	at TestNull.main(TestNull.java:4)
```

It seems that [this code](https://github.com/openjdk/jdk/blob/dc01604756c22889412f9f25b534488180327317/src/hotspot/share/prims/jni.cpp#L2879-L2881) forgets to handle the case where the original argument was null.

Thanks to Boris Rasin for reporting this issue in https://github.com/corretto/corretto-17/issues/145.