On Fri, 3 Jul 2026 14:41:09 GMT, Aleksey Shipilev <[email protected]> wrote:
>> Unsafe was changed recently through: >> https://github.com/openjdk/jdk/pull/31249 to no longer treat any non-zero >> byte read as a `boolean` through Unsafe as `true`, but only treat the >> 'canonical' representation, where only the least significant bit in the byte >> is set, as `true`. >> >> This change inadvertently leaked out through the memory access var handles. >> A user can write a `byte` into a memory segment (on or off-heap), and then >> read it back as a `boolean`, making this behavior change observable. Since >> the fallback linker depends on the previous behavior in the implementation, >> the tier5 test from the title was failing. But, there is really a gap in >> testing here, and we can observe the difference in behavior when just using >> the memory access parts of the API as well. >> >> It is important that the normalization of boolean values is the same in all >> these scenarios: >> - Normalizing a value returned from native code by a downcall >> - Normalizing an argument passed by native code to an upcall stub >> - Normalizing a value read from a memory segment using a var handle or the >> MemorySegment::get accessor >> >> To that end, this patch tweaks the memory segment var handles for boolean >> access to restore the old normalization behavior. I've also added the >> missing testing for this case. >> >> --------- >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). > > src/java.base/share/classes/java/lang/invoke/X-VarHandleSegmentView.java.template > line 76: > >> 74: return SCOPED_MEMORY_ACCESS.get$RawType$(bb.sessionImpl(), >> 75: bb.unsafeGetBase(), >> 76: offset(bb, base, offset)){#if[boolean]? != 0}; > > It is not exactly clear that `byte` and `boolean` are defined at the same > time. > > Could we / should we instead do: > > > #if[floatingPoint] > ... > #else[floatingPoint] > #if[byte] > ... > #else[byte] > #if[boolean] > ... > #else[boolean] > ... > #end[boolean] > #end[byte] > #end[floatingPoint] > > > ...or is it too ugly? Better, I think ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/31727#discussion_r3537785953
