`bugprone-nondeterministic-pointer-iteration-order` reported with custom comparator

[firewave]

#include <algorithm>
#include <vector>

struct S
{
    int i() const;
};

void f()
{
    std::vector<const S*> v;
    std::sort(v.begin(), v.end(), [](const S* s1, const S* s2){
        return s1->i() > s2->i();
    });
}

<source>:12:5: warning: sorting pointers is nondeterministic [bugprone-nondeterministic-pointer-iteration-order]
   12 |     std::sort(v.begin(), v.end(), [](const S* s1, const S* s2){
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   13 |         return s1->i() > s2->i();
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~
   14 |     });

https://godbolt.org/z/xjYe63rY6

This is only reported with libc++ (see #145667).

The warning should not be reported if a custom compare function is provided.

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: Oliver Stöneberg (firewave)

```cpp #include <algorithm> #include <vector>

struct S
{
int i() const;
};

void f()
{
std::vector<const S*> v;
std::sort(v.begin(), v.end(), [](const S* s1, const S* s2){
return s1->i() > s2->i();
});
}

<source>:12:5: warning: sorting pointers is nondeterministic [bugprone-nondeterministic-pointer-iteration-order]
12 | std::sort(v.begin(), v.end(), [](const S* s1, const S* s2){
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
13 | return s1->i() > s2->i();
| ~~~~~~~~~~~~~~~~~~~~~~~~~
14 | });

https://godbolt.org/z/xjYe63rY6

This is only reported with libc++.

The warning should not be reported if a custom compare function is provided.
</details>