RFR: 8354426: [ubsan] applying non-zero offset 34359738368 to null pointer in CompressedKlassPointers::encoding_range_end

[Martin Doerr]

On Fri, 11 Apr 2025 14:11:31 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> When running with ubsan enabled binaries on AIX, the HS jtreg test gc/epsilon/TestClasses (and some other tests too) show the following issue :
> 
> 
> /srcdir/jdk/src/hotspot/share/oops/compressedKlass.inline.hpp:98:16: runtime error: applying non-zero offset 34359738368 to null pointer
>     #0 0x90000001185d7ec in CompressedKlassPointers::encoding_range_end() make/hotspot/src/hotspot/share/oops/compressedKlass.inline.hpp:98
>     #1 0x90000001185d7ec in CompressedKlassPointers::print_mode(outputStream*) make/hotspot/src/hotspot/share/oops/compressedKlass.cpp:299
>     #2 0x900000012b6eb90 in Metaspace::global_initialize() make/hotspot/src/hotspot/share/memory/metaspace.cpp:847
>     #3 0x900000012b6d7d8 in universe_init() make/hotspot/src/hotspot/share/memory/universe.cpp:887
>     #4 0x900000012c3aa58 in init_globals() make/hotspot/src/hotspot/share/runtime/init.cpp:132
>     #5 0x900000012c6af7c in Threads::create_vm(JavaVMInitArgs*, bool*) make/hotspot/src/hotspot/share/runtime/threads.cpp:576
>     #6 0x900000012cb0548 in JNI_CreateJavaVM_inner(JavaVM_**, void**, void*) make/hotspot/src/hotspot/share/prims/jni.cpp:3587
>     #7 0x900000012cb0548 in JNI_CreateJavaVM make/hotspot/src/hotspot/share/prims/jni.cpp:3678
> 
> 
> Seems we add to a base (== nullptr) some offset which is reported as undefined behavior.
> On other OS the base might be different so we do not see it there.

LGTM.

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Marked as reviewed by mdoerr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/24596#pullrequestreview-2761345271