Pool size is doubled on each ordered_malloc call

[ptlopez]

Encountered a similar issue with: boostorg/pool#54 when I upgraded from boost 1.70 to 1.88. Repeated use of purge_memory() results in pool size extension with two times the previous size when ordered_malloc is called.

Sample Code:

int main()
{
    boost::pool<> bufferMemPool(sizeof(WCHAR), 32768);
    for (int i = 0; i < 10; i++)
    {
        LPWSTR buffer = static_cast<LPWSTR>(bufferMemPool.ordered_malloc());
        if (buffer) {
            std::wcout << "get_next_size(): " << bufferMemPool.get_next_size() << std::endl;
            bufferMemPool.ordered_free(buffer);
        }
        else {
            std::wcerr << L"Memory allocation failed." << std::endl;
        }

        bufferMemPool.purge_memory();
    }

    return 0;
}

Output:

get_next_size(): 65536
get_next_size(): 131072
get_next_size(): 262144
get_next_size(): 524288
get_next_size(): 1048576
get_next_size(): 2097152
get_next_size(): 4194304
get_next_size(): 8388608
get_next_size(): 16777216
get_next_size(): 33554432

[Lyeuiechang]

Cool stuff.😎 Wandering the best practices when using purge_memory() versus free().