On Fri, Oct 22, 2010 at 5:01 PM, Nevin Liber <nevin@eviloverlord.com> wrote:
On 22 October 2010 14:09, Daniel Walker <daniel.j.walker@gmail.com> wrote:
To make the example portable, you need to add a destructor to S1.
Why?
This is to force function_base::has_trivial_copy_and_destroy() to evaluate to false on line 971 of function_template.hpp. (Different compilers handle default destructors differently, so to force the same behavior on all platforms, you need to define a destructor.) The target function object is only cloned if it has a copy-constructor or destructor, since cloning is not necessary when swapping stateless function objects. Good question.
struct S1 { ~S1() {} void operator()() {} void* operator new(std::size_t, void* p) { // throw on third alloc if(++i == 3) throw std::bad_alloc(); return p = ::new S1(); } };
I just realized there is another technical error in my example, though it doesn't affect the behavior being demonstrated. That operator new is an in-place new, of course, so the return should be: return ::operator new (s, p); Thanks! Daniel Walker