RFR: JDK-8354316 : clang/linux build fails with -Wunused-result warning at XToolkit.c:695:9 [v2]

[Sergey Bylokhov]

On Wed, 14 May 2025 21:28:37 GMT, Harshitha Onkar <honkar at openjdk.org> wrote:

>> The following line results in unused-result warning on linux/clang.
>> 
>> 
>> /java.desktop/unix/native/libawt_xawt/xawt/XToolkit.c:695:9: error: ignoring return value of function
>>  declared with 'warn_unused_result' attribute [-Werror,-Wunused-result]
>>  695 | write ( AWT_WRITEPIPE, &wakeUp_char, 1 ); 
>> 
>> 
>> There are two ways to handle it 
>> 
>> 1) Make changes to XToolkit.c such that the warning is no longer thrown. But throwing an error based on the result of `write ( AWT_WRITEPIPE, &wakeUp_char, 1 );` will result in unexpected behavioral changes and the best way to handle it is to have an empty if block with an appropriate comment.
>> 
>> 
>> There was a discussion about the same line long ago and the reason the result of `write()` was not handled and it was left unchanged was not to introduce behavioral change - https://mail.openjdk.org/pipermail/awt-dev/2016-July/011626.html
>> 
>> 
>> 2) Add unused-result to disabled warning section for clang similar to gcc - https://github.com/openjdk/jdk/blob/d1543429ff29ca0d761b8473b3fb8621abcd226d/make/modules/java.desktop/lib/AwtLibraries.gmk#L281. The 1st approach was picked over the 2nd since the usual recommendation is not to add to disabled warning section unless there is no other option.
>> 
>> NOTE: the fix has been tested on linux/gcc , it does need to be tested on linux/clang.
>
> Harshitha Onkar has updated the pull request incrementally with one additional commit since the last revision:
> 
>   DTRACE added

Marked as reviewed by serb (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/25217#pullrequestreview-2841767253