Integrated: 8365229: ARM32: c2i_no_clinit_check_entry assert failed after JDK-8364269

[Aleksey Shipilev]

On Tue, 12 Aug 2025 14:06:35 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> When recording adapter entries, we record _offsets_, not the actual addresses:
> 
> 
>   entry_offset[3] = handler->get_c2i_no_clinit_check_entry() - i2c_entry;
> 
> 
> Every platform except ARM32 and Zero have all these entries set up, so offset are always sane. But those two platforms set up `nullptr` as `c2i_no_clinit_check_entry()`, because clinit barriers are unimplemented. So the new assert added in [JDK-8364269](https://bugs.openjdk.org/browse/JDK-8364269) fails encountering effectively `nullptr - i2c_entry` "garbage".
> 
> This PR is the second least horrible (IMO) fix for this: relaxing assert by checking that "out of range" values are actually wrapping around back to `0`/`nullptr`. Had to do it in unsigned ints to avoid UB. For the affected platforms, we do not actually access this problematic/garbage entry offset, since we are always checking if clinit barriers are enabled. So the assert is the only place where it matters.
> 
> The least horrible solution would be storing the actual `address`-es instead of `int` offsets. But that likely has footprint implications.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `runtime/cds` still works
>  - [x] Linux ARM32 server fastdebug, `java -version` now works
>  - [x] Linux x86_64 zero fastdebug, `make bootcycle-images` now works

This pull request has now been integrated.

Changeset: 9c266ae8
Author:    Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/9c266ae83c047025d778da41e413701ac3b50b03
Stats:     20 lines in 3 files changed: 11 ins; 1 del; 8 mod

8365229: ARM32: c2i_no_clinit_check_entry assert failed after JDK-8364269

Reviewed-by: kvn, adinn, bulasevich, phh

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PR: https://git.openjdk.org/jdk/pull/26746