RFR: 8314265: Fix -Wconversion warnings in miscellaneous runtime code [v3]

[Coleen Phillimore]

On Wed, 16 Aug 2023 13:01:53 GMT, Christian Hagedorn <chagedorn at openjdk.org> wrote:

>> This code:
>> 
>>       uint64_t isa;
>>       if (!_reader.read_uleb128(&isa, 4)) {
>>         // isa register is 4 bytes wide.
>>         return false;
>>       }
>>       _state->_isa = isa;  // only save 4 bytes
>> 
>> returns 64 bit of information into isa from this read_uleb128 call, even though it passes 4.
>
> I've quickly skimmed through the usages of `read_uleb128`. We only seem to be reading either directly into a proper `uint64_t` or we are reading 4 bytes (i.e. `check_size = 4`). In the latter case, we could either:
> - add a `static_cast` for the read value when storing it into a 32 bit field, as for example for `isa` above (i.e. `_state->_isa = static_cast<uint32_t>(isa)`).
> - provide a 32 bit `read_uleb128()` version that hides the casting.
> 
> I guess it's fine to just go with a `static_cast` when storing to a field for the few cases we have.

Thanks Christian.  I'll revert to use the static cast.  One of the cases has a comment why.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15233#discussion_r1295937366