Hi Valery,
> On 8 Aug 2018, at 09:10, Valery Kotov <kotov.val...@gmail.com> wrote:
>
> Hello all,
>
> I have a question about QV4 heap objects and what could be stored in them.
> I would like to move data structure from c++ heap to GC heap. Unfortunately,
> my data structure stores a pair of QLists internally.
> As far as I'm aware, QV4::Heap objects should be "trivially constructible",
> and thus, cannot store QList(s).
> One option would be to store QList pointer and manage it's lifecycle
> manually. But that does not sound like a good idea.
> I've noticed though, that some of qv4 types are using DECLARE_MARKOBJECTS
> macro. By using DECLARE_MARKOBJECTS macro and ObjectMember(s) define I can
> actually store a ValueArray member in my QV4 heap object.
>
> #define MyObjectMembers(class, Member) \
> Member(class, ValueArray, ValueArray, myValues)
>
> DECLARE_HEAP_OBJECT(MyObject, Object) {
> DECLARE_MARKOBJECTS(MyObject);
>
> In this case I can refer to myValues ValueArray type inside of MyObject.
> Unfortunately, it is a little bit unclear to me how to manage ValueArrays.
> From what I can see from some examples in the code (qv4generatorobject,
> qv4arraydata), it seems that I need to manage ValueArray manually.
> What I'm missing at the moment a little bit is how the actually allocation
> for ValueArray.values is done.
> I suspect that it is probably not done via plain "new" call. Otherwise it is
> a little bit confusing why not just to store the pointer directly.
>
> Could you guys please give me a few hints how to go about ValueArray
> management?
ValueArrays are allocated with a given size together with the object through
the memory manager. They are rather low level, and can’t be resized after
initial allocation. That means to get a larger ValueArray you need to allocate
a new object. Maybe what you need is closer to a Pointer to a SimpleArrayData.
Those are separately allocated by the memory manager, and you can grow the
array using SimpleArrayData::reallocate().
Cheers,
Lars
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