Please review this change which enables `-Wzero-as-null-pointer-constant` warnings in HotSpot code when building with gcc or clang.
There are three parts to this change. The first part augments the warning flags setup to support adding warning options that are only applied to HotSpot, rather than the JDK as a whole. There was previously some unused and possibly incomplete support for this when using gcc. Note that the Windows/Visual Studio support hasn't been tested much, and I think might not be working yet. I'm going to investigate that further in followup work. The second part enables `-Wzero-as-null-pointer-constant` for HotSpot code. This follows the guidance to avoid such in the HotSpot Style Guide. The third part removes a note in the HotSpot Style Guide about lingering uses of literal 0 as a null pointer constant. Those have been removed, and this change will block backsliding. Testing: mach5 tier1, GHA Sanity tests Integration of this change needs to wait for JDK-8376758. ------------- Commit messages: - remove obsolete note from style guide - enable -Wzero-as-null-pointer-constant for VM with gcc/clang - support hotspot-specific warnings Changes: https://git.openjdk.org/jdk/pull/29497/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29497&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8332189 Stats: 40 lines in 3 files changed: 14 ins; 13 del; 13 mod Patch: https://git.openjdk.org/jdk/pull/29497.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/29497/head:pull/29497 PR: https://git.openjdk.org/jdk/pull/29497
