Why garbage collection when RAII is available?

Question

I hear talks of C++14 introducing a garbage collector in the C++ standard library itself. What is the rationale behind this feature? Isn\'t this the reason that RAII exists in

Answer 1

None of the answers so far touch upon the most important benefit of adding garbage-collection to a language: In the absence of language-supported garbage-collection, it's almost impossible to guarantee that no object will be destroyed while references to it exist. Worse, if such a thing does happen, it's almost impossible to guarantee that a later attempt to use the reference won't end up manipulating some other random object.

Although there are many kinds of objects whose lifetimes can be much better managed by RAII than by a garbage collector, there's considerable value in having the GC manage nearly all objects, including those whose lifetime is controlled by RAII. An object's destructor should kill the object and make it useless, but leave the corpse behind for the GC. Any reference to the object will thus become a reference to the corpse, and will remain one until it (the reference) ceases to exist entirely. Only when all references to the corpse have ceased to exist will the corpse itself do so.

While there are ways of implementing garbage collectors without inherent language support, such implementations either require that the GC be informed any time references are created or destroyed (adding considerable hassle and overhead), or run the risk that a reference the GC doesn't know about might exist to an object which is otherwise unreferenced. Compiler support for GC eliminates both those problems.