RFR: 8357563: Shenandoah headers leak un-prefixed defines

[Aleksey Shipilev]

On Thu, 22 May 2025 12:36:07 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

> We hit a compilation error in ZGC when we defined a constant NumPartitions. This happened because there is a define name NumPartitions inside shenandoahFreeSet.hpp. I propose that this (and its friends) are hid inside the ShenandoahRegionPartitions class, which is the only user of these defines. An alternative would be to prefix the define with something that is unlikely to clash with other parts of HotSpot.
> 
> This PR is my suggestion for a change to solve this so this name conflict. Does this seem like an acceptable solution, or do you want something else? Thanks!

Nah, current version is fine. Folding this triad into a single constant would likely require dealing with signed-unsigned comparisons, casts back to enums, all that jazz. This would be a good starter task for our engineers.

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PR Comment: https://git.openjdk.org/jdk/pull/25392#issuecomment-2901614463