RFR: 8325163: Enable -Wpedantic on clang [v2]

[David Holmes]

On Mon, 5 Feb 2024 10:58:17 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

>> Inspired by (the later backed-out) [JDK-8296115](https://bugs.openjdk.org/browse/JDK-8296115), I propose to enable `-Wpedantic` for clang. This has already found some irregularities in the code, like mistakenly using `#import` instead of `#include`. In this patch, I disable warnings for these individual buggy or badly written files, but I intend to post follow-up issues on the respective teams to have them properly fixed.
>> 
>> Unfortunately, it is not possible to enable `-Wpedantic` on gcc, since individual warnings in `-Wpedantic` cannot be disabled. This means that code like this:
>> 
>> 
>> #define DEBUG_ONLY(code) code;
>> 
>> DEBUG_ONLY(foo());
>> 
>> 
>> will result in a `; ;`. This breaks the C standard, but is benign, and we use it all over the place. On clang, we can ignore this by `-Wno-extra-semi`, but this is not available on gcc.
>
> Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:
> 
>   FIx dtrace build

I think given the warnings have been enabled globally, but disabled locally where they cause build failures, and JBS issues will be filed for each of those special cases, then this is a reasonable change to make. It is then up to component teams to fix code where applicable, and enable disabled warnings in the future.

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PR Comment: https://git.openjdk.org/jdk/pull/17687#issuecomment-1928824757