RAII vs. Garbage Collector

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I recently watched a great talk by Herb Sutter about "Leak Free C++..." at CppCon 2016 where he talked about using smart pointers to implement RAII (Resource acquisition is initialization) - Concepts and how they solve most of the memory leaks issues.

Now I was wondering. If I strictly follow RAII rules, which seems to be a good thing, why would that be any different from having a garbage collector in C++? I know that with RAII the programmer is in full control of when the resources are freed again, but is that in any case beneficial to just having a garbage collector? Would it really be less efficient? I even heard that having a garbage collector can be more efficient, as it can free larger chunks of memory at a time instead of freeing small memory pieces all over the code.

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I even heard that having a garbage collector can be more efficient, as it can free larger chunks of memory at a time instead of freeing small memory pieces all over the code.

That's perfectly doable - and, in fact, is actually done - with RAII (or with plain malloc/free). You see, you don't necessarily always use the default allocator, which deallocates piecemeal only. In certain contexts you use custom allocators with different kinds of functionality. Some allocators have the in-built ability of freeing everything in some allocator region, all at once, without having to iterate individual allocated elements.

Of course, you then get into the question of when to deallocate everything - whether the use of those allocators (or the slab of memory with which they're associated has to be RAIIed or not, and how.

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