c++ custom compare function for std::sort()

Question

I want to create custom compare function for std::sort(), to sort some key-value pairs std::pair

Here is my function

 template 

        

Answer 1

Your comparison function is not even wrong.

Its arguments should be the type stored in the range, i.e. std::pair, not const void*.

It should return bool not a positive or negative value. Both (bool)1 and (bool)-1 are true so your function says every object is ordered before every other object, which is clearly impossible.

You need to model the less-than operator, not strcmp or memcmp style comparisons.

See StrictWeakOrdering which describes the properties the function must meet.