2013/2/13 Krzysztof Czainski <1czajnik@gmail.com>
2013/2/13 Nevin Liber <nevin@eviloverlord.com>
On 13 February 2013 07:20, Krzysztof Czainski <1czajnik@gmail.com> wrote:
Thank you, Nevin, for the above example. I think I see your point now. Furthermore, it gives me an idea
[...]
Note: there is a bit more work that has to be done for allocators than
just deriving from std::allocator<A>; for instance, rebind won't do the
right thing.
Oh, thanks, I'll try if that fixes my compiling errors and post results later.
I confirm, adding rebind<> fixed my example - it now works both with and without -std=c++11 (code attached).
I don't think this can be done for resize(), can it?
Works for resize too under C++11.
I mean the noinit_t trick - can that be done for resize just by writing an Allocator? I don't see how.
And so the last above question remains ;-) I'll elaborate on that: struct noinit_t {}; noinit_t const noinit = {}; template < class T > struct MyAllocator : std::allocator<T> { using std::allocator<T>::construct; // for v.emplace_back(noinit); void construct( T* c, noinit_t ) { ::new (static_cast<void*>(c)) T; // note: T; instead of T(); } template < class U > struct rebind { typedef MyAllocator<U> other; }; }; int main() { namespace cont = boost::container; cont::vector< int, MyAllocator<int> > vi; vi.emplace_back(5); vi.pop_back(); vi.emplace_back(noinit); assert( 0 != vi.back() ); vi.pop_back(); vi.resize( 1, noinit ); // !!! assert( 0 != vi.back() ); } vi.resize( 1, noinit ) does't compile - and it shouldn't, but my question is, can I get the desired effect: leave default resize as is, and have an overload that doesn't zero-initialize PODs? Cheers, Kris