RFR: 8377895: Create sizeof_auto, to reduce narrowing conversions [v2]

[Johan Sjölen]

On Mon, 16 Feb 2026 14:00:38 GMT, Leo Korinth <lkorinth at openjdk.org> wrote:

>> src/hotspot/share/oops/cpCache.hpp line 199:
>> 
>>> 197: 
>>> 198:  public:
>>> 199:   static int size() { return align_metadata_size(sizeof_auto<ConstantPoolCache>() / wordSize); }
>> 
>> Surely, this should no be a part of this PR?
>
> This line of code is one of the /reasons/ for implementing `sizeof_auto`. Without `sizeof_auto` this expression creates an implicit narrowing conversion (a warning in my emacs, and hopefully a compiler error soon). I can remove the change, but I thought it was a nice way to show its value. 
> 
> Do you still want me to remove the fix for an implicit narrowing conversion?

OK, I think we can keep it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29716#discussion_r2815909635