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

[Magnus Ihse Bursie]

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

This PR triggered a lot of discussion about C++ standards, gcc behavior, and possible breaches of coding standards in Hotspot -- but not a lot of discussion about the actual content of the PR.

Is there anything in this proposed PR that you gentlemen disagree with or object to? Or is this fine to push as a step in our ongoing pursuit of increasing the code quality, that can (and will) be followed by many more?

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PR Comment: https://git.openjdk.org/jdk/pull/17687#issuecomment-1927365995