C++ Weird behavior on function parameter references

I've just found something really weird, check out this code:

#include <vector>
using namespace std;

class A {
    public:
    int n = 0;
    A(const char* p) { n = strlen(p); };
};
void F(vector<pair<const char*, const A&>> v) {
    printf("F\n");
    for(vector<pair<const char*, const A&>>::iterator it = v.begin();it!=v.end();++it) printf("  '%s': %p %i\n", it->first, &it->second, it->second.n);
};

int main(int, char**) {
    F({
            { "A", "A" },
            { "B", "BB" },
            { "C", "CCC" },
            { "D", "DDDD" }
        });
};

Now compile it with clang++ -std=c++11 -Wall -Wextra -Wpedantic -O0 main.cc -o main, or something similar (with optimization disabled).

And you should see an output like this:

F
  'A': 0x7fff57a0b988 1
  'B': 0x7fff57a0b9d0 2
  'C': 0x7fff57a0ba18 3
  'D': 0x7fff57a0ba60 4

Which is nice, the compiler automatically creates the vector object and the corresponding A& references, which are all different.

Now, compile it with clang++ -std=c++11 -Wall -Wextra -Wpedantic -O1 main.cc -o main, notice how I just added the lowest level of optimization.

And you would see,

F
  'A': 0x7fff5ac54b30 1629262454
  'B': 0x7fff5ac54b30 1629262454
  'C': 0x7fff5ac54b30 1629262454
  'D': 0x7fff5ac54b30 1629262454

that all parameters reference the same A& object, which I find wrong.

Here are my compiler details:

Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn)
Target: x86_64-apple-darwin14.1.0
Thread model: posix

Is this expected behavior? Is this a compiler bug?