David Abrahams wrote:
Joaqu?n M? L?pez Mu?oz <joaquin@tid.es> writes:
The new rule introduced in Boost.Serialization that forbids saving of non-const objects has proved a little controversial. My point of view is that the rule, albeit far from perfect, provides some level of safety against hard to track errors. Others' opinions differ.
The current rule is a rough approximation to what IMHO would constitute the right enforcement: everytime a trackable object is saved, check wether an object with the same address has been previously saved and, if so, make sure that the object didn't change.
I don't understand what bugs this is going to catch. Certainly in this case,
for( ... X x(... ); ar << x;
the low-level problem isn't that x is changing, but that it's a different object each time. Two temporally different x's might well be identical.
But all of this misses the high-level problem: the author of the code doesn't know what he's doing. You simply can't serialize objects from distinct scopes with tracking into the same archive, because there may be aliasing.
Now the key question. Why do I need the tracking if I never save an object with the same address both by pointer and by value. I don't. In some other part of program, I might be serializing vector<X*>, but as long as none of those pointers point to stack objects, I don't need tracking in the above loop. And serialization library insist on tracking just because somewhere else in the program pointer to X is serialized. - Volodya