re http://gcc.gnu.org/ml/gcc-help/2010-02/msg00055.html Modify the move constructor slightly, to show 'this' as well as 'f' and it becomes clear: foo (foo && f) { std::cout << "Cr " << this << ' ' << &f << "\n"; } gives ---- C 0x7fff0df100de C 0x7fff0df100df operator A|B{{ Cr 0x16c0010 0x7fff0df100df Cr 0x16c0031 0x7fff0df100de Cr 0x16c0030 0x16c0010 }} ---- so I hope you can see that an object is move-constructed at location 0x16c0010 from lhs, then another object is move-constructed at 0x16c0031 from rhs, then the object at 0x16c0010 is moved to 0x16c0030. The second push_back causes a reallocation, which moves ret[0] If you add ret.reserve(2) before the calls to push_back you don't get the reallocation: ---- C 0x7ffff943f68e C 0x7ffff943f68f operator A|B{{ Cr 0xbaa010 0x7ffff943f68f Cr 0xbaa011 0x7ffff943f68e }} ---- This is really nothing to do with rvalues, but rather vector's reallocation policy. Hope that helps, Jonathan
