RFR: 8331298: avoid alignment checks in UBSAN enabled build

[Martin Doerr]

On Mon, 29 Apr 2024 12:15:55 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> Currently we run into some alignment related issues when building with '--enable-ubsan' . Those errors already occur in the build. Fixing them might take some time and maybe also some discussion if it is worth the effort ,
> So for now the alignment related checks should be disabled to get the UBSAN build working.
> Example :
> 
> /jdk/src/hotspot/cpu/x86/macroAssembler_x86.hpp:128:13: runtime error: store to misaligned address 0x15099c3cf4ce for type 'int', which requires 4 byte alignment
> 0x15099c3cf4ce: note: pointer points here
>  00 80 0f 86 00 00 00 00 3d 06 00 00 80 76 60 3d 07 00 00 80 76 40 3d 08 00 00 80 76 20 3d 1e 00
>              ^
>     #0 0x1509b3b04f10 in MacroAssembler::pd_patch_instruction(unsigned char*, unsigned char*, char const*, int) /jdk/src/hotspot/cpu/x86/macroAssembler_x86.hpp:128
>     #1 0x1509b3b04f10 in Label::patch_instructions(MacroAssembler*) /jdk/src/hotspot/share/asm/assembler.cpp:201
>     #2 0x1509b940b6d8 in VM_Version_StubGenerator::generate_get_cpu_info() /jdk/src/hotspot/cpu/x86/vm_version_x86.cpp:381
>     #3 0x1509b94059bd in VM_Version::initialize() /jdk/src/hotspot/cpu/x86/vm_version_x86.cpp:2138
>     #4 0x1509b93fb56e in VM_Version_init() /jdk/src/hotspot/share/runtime/vm_version.cpp:32
>     #5 0x1509b61ef947 in init_globals() /jdk/src/hotspot/share/runtime/init.cpp:126
>     #6 0x1509b8fb0e29 in Threads::create_vm(JavaVMInitArgs*, bool*) /jdk/src/hotspot/share/runtime/threads.cpp:553
>     #7 0x1509b67da3d7 in JNI_CreateJavaVM_inner /jdk/src/hotspot/share/prims/jni.cpp:3581
>     #8 0x1509b67da3d7 in JNI_CreateJavaVM /jdk/src/hotspot/share/prims/jni.cpp:3672
>     #9 0x1509c0eed957 in InitializeJVM /jdk/src/java.base/share/native/libjli/java.c:1550
>     #10 0x1509c0eed957 in JavaMain /jdk/src/java.base/share/native/libjli/java.c:491
>    ... (rest of output omitted)

I wish we could fix all UB, but that seems unrealistic for the time being. LGTM.

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Marked as reviewed by mdoerr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18998#pullrequestreview-2028402095