new运算符分配内存地址的顺序及链表连续创建节点的内存地址是否递增问题

Great question! Let's cut straight to the core: there’s no universal, guaranteed order for memory addresses allocated by new—it all hinges on the underlying memory allocator implementation, your operating system, and even the current state of the heap.

Most common allocators (like glibc’s ptmalloc on Linux or Windows’ default allocator) tend to allocate memory in an upward-growing fashion when the heap is fresh and free of fragmentation. That means your first new call might grab a lower address, and subsequent calls get higher ones—but this is just a common behavior, not a hard rule.

If the heap has freed blocks (from previous delete calls, for example), the allocator will often reuse those existing blocks instead of expanding the heap. In that case, a newly allocated block could end up with an address lower than a previous one. Some allocators also have specialized strategies for different allocation sizes, which might cause addresses to jump between separate memory regions.

Short answer: Probably, but never rely on it.

If you’re creating nodes back-to-back with no other memory allocations or deallocations in between, you’ll likely see incrementing addresses (since the allocator is just grabbing fresh, contiguous heap space). For example, this C++ snippet might print addresses in increasing order:

#include <iostream>

struct Node { int val; Node* next; };

int main() {
    Node* n1 = new Node;
    Node* n2 = new Node;
    Node* n3 = new Node;
    std::cout << n1 << "\n" << n2 << "\n" << n3 << "\n";
    delete n1; delete n2; delete n3;
    return 0;
}

But introduce any deallocation or unrelated allocations in between, and this pattern breaks. Take this example:

Node* n1 = new Node;
Node* n2 = new Node;
delete n1;
Node* n3 = new Node; // n3 might reuse n1's old address, which is lower than n2's

Here, n3’s address would be lower than n2’s, shattering the "递增" expectation.

Critical Rule to Remember #

Never write code that depends on memory addresses being in a specific order. This is undefined behavior—your code might work on one system, break on another, or even fail between runs on the same machine. Linked lists should always use explicit pointer links (next/prev pointers) to maintain their structure, not address comparisons.

内容的提问来源于stack exchange，提问作者nikhilreddydev