RFR: 8313249: Fix -Wconversion warnings in verifier code [v4]

[Coleen Phillimore]

On Mon, 31 Jul 2023 19:12:49 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add another static_cast
>
> src/hotspot/share/classfile/stackMapTableFormat.hpp line 552:
> 
>> 550:   static u1 appends_to_frame_type(int appends) {
>> 551:     assert(appends > 0 && appends < 4, "Invalid append amount");
>> 552:     return static_cast<u1>(251 + appends);
> 
> The problem I have with assert + unchecked cast in general is that future maintainers might accidentally remove or break the assert check so we are left with an unchecked cast that truncates out-of-range values.  For that reason I would like to see a checked_cast here.  Even if we could do something like `RangeCheckedInt<1,3> appends` and get rid of the assert, I would probably keep the checked_cast because it catches human error.

Ok, I'll change both of them in this file.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15056#discussion_r1279778554