RFR: 8313882: Fix -Wconversion warnings in runtime code [v6]

[Coleen Phillimore]

On Wed, 9 Aug 2023 20:02:31 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - put checked_cast around getc().
>>  - put checked_cast around getc().
>
> src/hotspot/share/runtime/arguments.cpp line 1183:
> 
>> 1181:   bool result         = true;
>> 1182: 
>> 1183:   char c = checked_cast<char>(getc(stream));
> 
> I think this only works if "char" is signed, because EOF is -1.  What I meant was:
> 
> int c0 = getc(stream);
> while (c0 != EOF ...) {
>   char c = checked_cast<char>(c0);
>   ...
>   c0 = getc(stream);

I don't see this as any cleaner than having the checked_cast in the place where we need to store a char.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15177#discussion_r1289144572