RFR: 8255285: Move JVMFlag origins into a new enum JVMFlagOrigin [v2]

[Claes Redestad]

On Mon, 26 Oct 2020 22:20:28 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> Many JVM function take an `JVMFlag::Flags` parameter to indicate the origin of the flag -- i.e., "who is setting this flag". E.g., in arguments.hpp:
>> 
>> static bool parse_argument(const char* arg, JVMFlag::Flags origin);
>> 
>> However, `JVMFlag::Flags` contains many other bits that are unrelated to the origin. We should add a new enum `JVMFlagOrigin` that has only the valid values for the origin. This makes it possible to do more type-safety checks at C++ compilation time.
>> 
>> This patch also renamed the confusing bit `JVMFlag::ORIG_COMMAND_LINE` to `WAS_SET_IN_COMMAND_LINE` and added documentation, so that it won't be confused with `JVMFlagOrigin::COMMAND_LINE`.
>
> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Removed aliases of JVMFlagOrigin::X as JVMFlag::X

Marked as reviewed by redestad (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/823