RFR: 8313874 - JNI NewWeakGlobalRef throws exception for null arg [v2]

[David Holmes]

On Tue, 8 Aug 2023 12:22:38 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> src/hotspot/share/prims/jni.cpp line 2879:
>> 
>>> 2877:   Handle ref_handle(thread, JNIHandles::resolve(ref));
>>> 2878:   jweak ret = JNIHandles::make_weak_global(ref_handle, AllocFailStrategy::RETURN_NULL);
>>> 2879:   if (ret == nullptr && ref_handle != nullptr) {
>> 
>> That isn't how you check a Handle for null content - you need `!ref_handle.is_null()`.
>
> even better would be `ref_handle.not_null()`.  Though I think the comparison does work.

Yes it seems that some implicit Handle conversions were removed at some point which now makes direct comparison to `nullptr` allowable - somewhat obsolescing the `is_null()/not_null()` helper methods.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15188#discussion_r1287687902