Difference Between Stack and stack

Difference Between Stack and stack

// Record the problem.

Management Method: For stacks, it is automatically managed by the compiler without manual control. For heaps, the release work is controlled by programmers and memory leak is easily generated.

1. application size:
STACK: in Windows, a stack is a data structure extended to a low address and a continuous memory area. This statement indicates that the stack top address and the maximum stack capacity are pre-defined by the system. In WINDOWS, the stack size is 2 MB (OR 1 MB, in short, it is a constant determined during compilation. If the requested space exceeds the remaining space of the stack, overflow will be prompted. Therefore, the space available from the stack is small.

Heap: the heap is a data structure extended to the high address and a non-sequential memory area. This is because the system uses the linked list to store the idle memory address, which is naturally discontinuous, And the traversal direction of the linked list is from the low address to the high address. The heap size is limited by the valid virtual memory in the computer system. It can be seen that the space obtained by the heap is flexible and large.

2. fragmentation problem: for the heap, frequent new/delete operations will inevitably lead to memory space disconnections, resulting in a large number of fragments and reduced program efficiency. For the stack, this problem will not exist, because the stack is an advanced and outgoing queue, they are so one-to-one correspondence, it is impossible to have a memory block popped up from the middle of the stack.

3. allocation method: the heap is dynamically allocated without static allocation. There are two stack allocation methods: static allocation and dynamic allocation. Static allocation is completed by the compiler, such as local variable allocation. Dynamic Allocation is implemented by the alloca function, but the stack dynamic allocation is different from the heap dynamic allocation. Its Dynamic Allocation is released by the compiler without manual implementation.

4. allocation Efficiency: the stack is the data structure provided by the machine system, and the computer will provide support for the stack at the underlying layer: allocate a dedicated register to store the stack address, the output stack of the Pressure Stack has dedicated Command Execution, which determines the high efficiency of the stack. The heap is provided by the C/C ++ function library, and its mechanism is very complicated.