RFR: 8275004: CDS build failure with gcc11

[Aleksey Shipilev]

On Sun, 10 Oct 2021 10:12:54 GMT, Jie Fu <jiefu at openjdk.org> wrote:

> I think `<cstddef>` is enough since the failure was caused by undefined `size_t`. Why `globalDefinitions.hpp` is better here? 

I believe it is a good style to avoid including standard headers directly. 

While Hotspot Style Guide [permits](https://github.com/openjdk/jdk/blob/master/doc/hotspot-style.md#c-standard-library) using `cstddef` directly for `std::nullptr_t`, it does not directly allow it for `size_t` (if we follow this rule exactly). Moreover, it suggests to use a hotspot header even for the allowed cases. There is the only case of `std::nullptr_t` use in `oopsHierarchy.hpp`, and it still includes `cstddef` through `globalDefinitions.hpp`. Therefore it is reasonable to do the same here.

(Also, includes should be in alphabetic order, if you change it).

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PR: https://git.openjdk.java.net/jdk/pull/5880