RFR: 8263718: unused-result warning happens at os_linux.cpp

[Magnus Ihse Bursie]

On Wed, 17 Mar 2021 23:08:31 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>> Did you notice this workaround in the gcc bug report?
>> 
>> "Note that a logical negation prior to cast to void is sufficient to suppress the warning:
>> 
>>   int void_cast_should_not_warn() {
>>      (void) !foo();
>>      //     ^-- here
>>      return 0;
>>   }
>> "
>
>> "Note that a logical negation prior to cast to void is sufficient to suppress the warning:
>> 
>> ```
>>   int void_cast_should_not_warn() {
>>      (void) !foo();
>>      //     ^-- here
>>      return 0;
>>   }
>> ```
>> 
>> "
> 
> The warning has gone with `(void)!`, but isn't is strange a bit? IMHO code changes or pragma (or compiler option) are suitable than it.

I can't really comment on which is better -- it's up to you hotspot developers.

Nevertheless, my personal preference is that `(void)` would have been best since it's a well-established idiom. If gcc is buggy about this, then I think I'd preferred to use this workaround with a comment `// the ! is needed to workaround gcc bug`, to keep with the idiom as much as possible. Pragmas also work, but I personally consider them ugly and a last resort. But once again, don't listen to what I'm saying :-)

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PR: https://git.openjdk.java.net/jdk/pull/3042