c++, sorting of custom object: requirements of the comparison function

I have a vector of pointer of a custom object std::vector<MyObject*>. The object has an index, a number and a timestamp (time of creation of the object). The timestamp is unique, the number can be either -1 (the object is not been assigned a number yet) or a positive value; if the object has a number greater than 0, the number is unique.

class MyObject {private:    int id;    int number;    time_t timestamp;public:    MyObject(int id, int number, time_t timestamp) : id(id), number(number), timestamp(timestamp) {}};

I want to order the vector using a custom comparison function: if the two instances of my object have a number, I order using the number (descending), if not I order using the timestamp (descending).

So I added the following to the MyObject class:

    static bool compareByDescendingNumberAndTimestamp(MyObject * a, MyObject * b) {        if (a->number > 0 && b->number > 0) {            return a->number > b->number;        }        return a->timestamp > b->timestamp;    }

And finally sort the vector:

std::vector<MyObject*> myObjects;auto object1 = new MyObject(1, 24097, 1200);auto object2 = new MyObject(2, 24096, 1100);auto object3 = new MyObject(3, -1, 1000);auto object4 = new MyObject(4, -1, 900);auto object5 = new MyObject(5, 24099, 800);auto object6 = new MyObject(6, 24095, 850);myObjects.push_back(object1);myObjects.push_back(object2);myObjects.push_back(object3);myObjects.push_back(object4);myObjects.push_back(object5);myObjects.push_back(object6);std::sort(myObjects.begin(), myObjects.end(), MyObject::compareByDescendingNumberAndTimestamp);

The order I intended to have is the following:

ID   Number  Timestamp5    24099    8001    24097   12002    24096   11003    -       10004    -        9006    24095    850

But what I actually got is:

ID   Number  Timestamp1    24097   12002    24096   11003    -       10004    -        9005    24099    8006    24095    850

After some research I find this page. As far as I understood, my comparison function does not satisfy the requirements of Compare. In particular the comp(a, b) does not establish a strict weak ordering relation.

Is there a way I can write a comparison function to order my vector as I want?

Note: I've been using c++17.

Edit:

Minimal reproducible example (notice that the initail order of the vector influences the end result):

#include <iostream>#include <vector>#include <algorithm>#include <string>class MyObject {public:    int id;    int number;    time_t timestamp;    MyObject(int id, int number, time_t timestamp) : id(id), number(number), timestamp(timestamp) {}    static bool compareByDescendingNumberAndTimestamp(MyObject * a, MyObject * b) {        if (a->number > 0 && b->number > 0) {            return a->number > b->number;        }        return a->timestamp > b->timestamp;    }};int main() {    std::vector<MyObject*> myObjects;    auto object1 = new MyObject(1, 24097, 1200);    auto object2 = new MyObject(2, 24096, 1100);    auto object3 = new MyObject(3, -1, 1000);    auto object4 = new MyObject(4, -1, 900);    auto object5 = new MyObject(5, 24099, 800);    auto object6 = new MyObject(6, 24095, 850);    myObjects.push_back(object6);    myObjects.push_back(object5);    myObjects.push_back(object4);    myObjects.push_back(object3);    myObjects.push_back(object2);    myObjects.push_back(object1);    std::sort(myObjects.begin(), myObjects.end(), MyObject::compareByDescendingNumberAndTimestamp);    std::cout << "ID\tNumber\tTimestamp" << std::endl;    for (auto const & object: myObjects) {        std::cout << std::to_string(object->id) << "\t" << std::to_string(object->number) << "\t"<< std::to_string(object->timestamp) << std::endl;    }    return 0;}