RFR: 8259894: refactor parts of jvm.h into jvm_io.h and jvm_constants.h [v2]

[Ioi Lam]

On Wed, 20 Jan 2021 06:07:19 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   David Holmes comments
>
> src/hotspot/share/runtime/os.hpp line 28:
> 
>> 26: #define SHARE_RUNTIME_OS_HPP
>> 27: 
>> 28: #include "jvm_md.h"
> 
> jvm_md.h should not be included directly by any file - it is an internal implementation detail.

os.hpp is used by almost all HotSpot .o files, so if we keep jvm.h here, that defeats the purpose of this PR. As David and I discussed offline, jvm_md.h is a kludgy legacy porting layer for stuff like DIR, which is used by os.hpp.

jvm_md.h contains comments like the following that haven't been touched for decades .... so it's probably a good idea to not disturb it now.

/*
 * This file is currently collecting system-specific dregs for the
 * JNI conversion, which should be sorted out later.
 */

-------------

PR: https://git.openjdk.java.net/jdk/pull/2154