lockfree queue allocation problem

[pn.suzuki.kojiro@…]

The default constructor of boost::lockfree::queue<int>
try to allocate 0xffffffffffffffff elements for pool.

Revision: 81719, queue.hpp, line 154

        pool(node_allocator(), capacity)

"capacity" is 0xffffffffffffffff in my environment(VS 2012 Express for Desktop).

The other constructors works fine.

The problem occurred on both of 32bit and 64bit.
(in 32bit, the "capacity" was 0xffffffff)

[timblechmann]

not a bug: you have not configured the queue to have a capacity that is specified at compile time, so you should not use the default constructor. there is a run-time assertion, but unfortunately that fires after the memory pool is constructed with -1, which is a bit confusing. let me see, if i can improve that a bit ...

[pn.suzuki.kojiro@…]

Why don't you split implementation by have_capacity?

[timblechmann]

possible, but increases the complexity of the code as one would need an additional abstraction layer.

[pn.suzuki.kojiro@…]

I don't understand yet, why can't I use the default constructor in this case?
I thought that the default constructor should constructs empty queue with empty pool.

        pool(node_allocator(), has_capacity ? capacity : 0)

Does this code have a problem?

[timblechmann]

if you don't specify a capacity, internal nodes have to be allocated during push() or pop() ... since memory allocation is not lock-free the data-structure is not lock-free anymore ...

[Kojiro Suzuki <pn.suzuki.kojiro@…>]

Thank you for your answers, I understand it now.

I have an idea.
If you use the the previous code, and leave the assertion,
it generates assertion without trying to allocate huge elements.

    queue(void):
        head_(tagged_node_handle(0, 0)),
        tail_(tagged_node_handle(0, 0)),
        pool(node_allocator(), has_capacity ? capacity : 0) // add this
    {
        BOOST_ASSERT(has_capacity); // and leave this
        initialize();
    }