RFR: 8320353: Reenable stringop-overflow warnings

[Kim Barrett]

On Tue, 1 Jul 2025 12:25:04 GMT, Anton Artemov <duke at openjdk.org> wrote:

> Hi, please consider the following changes:
> 
> this PR addresses the issue of stringop-overflow warnings produced by GCC. The compiler does think that the thread pointer returned by `JavaThread::current()` can be null, though it cant. The thread pointer ends up being an argument in `__atomic_load`, and the compiler reports the warning related to argument of that method. 
> 
> The patch adds a hint to the compiler by means of `__builtin_unreachable()` intrinsic, which tells the compiler that certain piece of code will never be reached (case of thread pointer being null). This solves the issue. 
> 
> Tested in tiers 1-3 and GHA.

make/hotspot/lib/CompileJvm.gmk line 199:

> 197:     DISABLED_WARNINGS_gcc_macroAssembler_ppc_sha.cpp := unused-const-variable, \
> 198:     DISABLED_WARNINGS_gcc_postaloc.cpp := address, \
> 199:     DISABLED_WARNINGS_gcc_shenandoahLock.cpp := stringop-overflow, \

What about this one in shenandoahLock.cpp?

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PR Review Comment: https://git.openjdk.org/jdk/pull/26067#discussion_r2181357398