DESIGN DOC: https://wiki.openjdk.java.net/display/HotSpot/HotSpot+Command-Line+Flags+Overhaul+-+Design+Doc

(The below description is a bit out-dated. Will fix soon. For now please refer to the link above for motivation and proposed design).
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Currently all JVM flags are grouped under a giant macro ALL_FLAGS

http://hg.openjdk.java.net/jdk/jdk/file/2fbc66ef1a1d/src/hotspot/share/runtime/globals.hpp#l2539

This is very hard to maintain. Erik Österlund and Stefan Karlsson have suggested a new design where flags can be individually maintain by different modules. The basic idea is to declare a flag like this in a header file:

extern int SomeFlag;

and then define the flag in a C file:

int SomeFlag = initial_val;
ProductFlag Flag_SomeFlag("SomeFlag, &SomeFlag, .....);

We can build up a list of all the ProductFlags in the VM (using C++ static initialization) for command-line processing, etc.

class ProductFlag {
    static ProductFlag* _head;
    ProductFlag* _next;
    void* _value_addr;
    char* _name;
public:
    ProductFlag(char* name, void* valid_addr, ...) {
        _name = name;
        _value_addr = value_addr;
        _next = _head;
        _head = this;
        ...
    }
};

This list will replace the flagTable[] in

http://hg.openjdk.java.net/jdk/jdk/file/2fbc66ef1a1d/src/hotspot/share/runtime/flags/jvmFlag.cpp#l825