RFR: JDK-8281003 - MethodHandles::lookup throws NPE if caller is null

[Alan Bateman]

On Mon, 14 Feb 2022 18:03:45 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/invoke/MethodHandles.java line 121:
>> 
>>> 119:         Class<?> c = Reflection.getCallerClass();
>>> 120:         if (c == null) {
>>> 121:             throw new IllegalCallerException();
>> 
>> Throwing ICE is probably okay here, I just wonder if there is any practical advantage to having it return publicLookup instead, e.g. is there any scenario where a JNI attached thread might want to invoke a method with a Lookup parameter?
>
> `MethodHandles::publicLookup` can be called instead to get a public Lookup to invoke a method with a Lookup parameter.   The dilemma here is whether the API should be made null-caller friendly or using a proper API `MethodHandles::publicLookup` for such case.

You are right. If a JNI attached thread with no Java frames wants a Lookup then it can invoke publicLookup. I think the proposal here is good.

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PR: https://git.openjdk.java.net/jdk/pull/7447