RFR: 8319117: GrowableArray: Allow for custom initializer instead of copy constructor

[Quan Anh Mai]

On Sun, 29 Oct 2023 14:00:25 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

> Hi, 
> 
> When using at_put and at_put_grow you can provide a value which will be supplied to the constructor of each element. In other words, you can intialize each element through a copy constructor.
> 
> I suggest that we also provide a function equivalent where the function is provided a pointer to the memory to be initialized. This can be used for `NONCOPYABLE` classes, for example.
> 
> This is implemented using a SFINAE pattern because `nullptr` introduces ambiguity if you use static overload.
> 
> Currently running tier1-tier4.

I think a more preferable approach is to do emplace-like filling

    template <class... Args>
    E& at_grow(int i, Args... args) {
        assert(0 <= i, "negative index %d", i);
        if (i >= this->_len) {
            if (i >= this->_capacity) {
                grow(i);
            }
            for (int j = this->_len; j <= i; j++) {
                _data[j].~E();
                new (&_data[j]) E(args...);
            }
            this->_len = i + 1;
        }
        return _data[i];
    }

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PR Comment: https://git.openjdk.org/jdk/pull/16409#issuecomment-1786876601