RFR: JDK-8299386: Refactor metaprogramming to use <type_traits>

[Kim Barrett]

On Mon, 2 Jan 2023 09:15:16 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> Just a general question with regards too our style guide. What is the goal/idea behind this line? https://github.com/openjdk/jdk/blame/2ee34f14880cccca02e2933f80b000979f33c6d1/doc/hotspot-style.md#L578
> 
> > TODO: Rather than directly #including (permitted) Standard Library headers, use a convention of #including wrapper headers (in some location like hotspot/shared/stdcpp). This provides a single place for dealing with issues we might have for any given header, esp. platform-specific issues.
> 
> And is it relevant for any/all of these <type_trait> / metaprogramming changes?

This is kind of a hint / reminder / statement of intent for future direction,
particularly if/when we start permitting the use of more of the Standard
Library.  There were questions about whether we were going to do that and how
we might control it, back when I was doing the large revision of this document
for C++14 support.  It currently has no real force (it's a TODO item after all),
and probably doesn't really belong in the current document.  But there are
continuing discussions about opening up some amount of StdLib usage.

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PR: https://git.openjdk.org/jdk/pull/11794