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

[Harshitha Onkar]

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.

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.

-------------

Commit messages:
 - unused-result changes

Changes: https://git.openjdk.org/jdk/pull/25217/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25217&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8354316
  Stats: 7 lines in 2 files changed: 5 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25217.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25217/head:pull/25217

PR: https://git.openjdk.org/jdk/pull/25217