C ++ STL问题：分配器

Question

I have a (potentially dumb) question about the C++ STL. When I make a container (vector, set, map, etc), is it allocated on the stack or on the heap? If I make a set and put 5 million strings, will I have to worry about a stack overflow?

Answer 1

默认情况下，STL类从堆中分配其内部缓冲区，尽管这些类还允许自定义分配器允许用户指定要从中分配的备用位置 - 例如共享内存池。

Answer 2

The default allocator for STL containers uses operator new and delete, so it's whatever those route to for the type being contained. (In general, it comes from the heap unless you do something to override that.)

You will not get a stack overflow from allocating 5 million strings. Even if you made a stack based allocator, it would probably overflow before you even inserted one string.

Answer 3

The container itself is allocated where you decide (it can be the stack, the heap, an object's member, etc) but the memory it uses is, by default, as others described, taken on the Free Store (managed through new and delete) which is not the same as the heap (managed through malloc/free).

Don't mix the two!