RFR: 8325163: Enable -Wpedantic on clang

[Magnus Ihse Bursie]

On Fri, 2 Feb 2024 15:22:03 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.

Ah, dtrace triggers `dollar-in-identifier-extension`. Of course...  *sigh*

I actually had this disabled for hotspot on an earlier version of the patch (that had lied dormant in my personal fork for about a year), but I could not reproduce the problem it was supposed to solve now, so I removed it again. Now I know why I had it.

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PR Comment: https://git.openjdk.org/jdk/pull/17687#issuecomment-1925848001