On Sun, Oct 21, 2018 at 04:15:58PM +0200, Elvis Stansvik wrote: > In order to try out the unsafe usage you suggested in your other mail, > and also another unsafe usage pointed out in an SO question > (https://stackoverflow.com/questions/39051460/why-does-as-const-forbid-rvalue-arguments/39051612#39051612), > I made the following test program. > > The output when running is: > > [estan@newton move-to-const-test]$ ./move-to-const-test > without moveToConst: > FooPrivate constr from vector > Foo constr with arg 0x7fffdb627200 > Foo begin 0x7fffdb627200 > Foo end 0x7fffdb627200 > Foo destr 0x7fffdb627200 > FooPrivate destr > > with moveToConst: > FooPrivate constr from vector > Foo constr with arg 0x7fffdb627208 > Foo move constr 0x7fffdb627210 > Foo destr 0x7fffdb627208 > Foo begin const 0x7fffdb627210 > Foo end const 0x7fffdb627210 > Foo destr 0x7fffdb627210 > FooPrivate destr > [estan@newton move-to-const-test]$ > > Which just shows it's working as intended.
I have (a) no example that triggers obviously bad behaviour and (b) a bad gut feeling nevertheless. The problem is that a 'move' could be a 'swap' in practice, with the to-be-destroyed object held 'for a while', effectively turning C++'s rather deterministic destruction behaviour into something resembling garbage collection. I wouldn't be surprised if one can cause real problems with 'random' destruction orders on non-memory resources, like files. Simple memory might be safe(r), as releasing order does typically not matter. Andre' _______________________________________________ Development mailing list Development@qt-project.org http://lists.qt-project.org/mailman/listinfo/development
