Is escaping of a temp variable valid?

[Joey Ye]

Running into an unexpected result with GCC with following case, but
not sure if it is a valid C++ case.

#define nullptr 0
enum nonetype { none };

template<typename T>
class class_zoo {
  public:
    const T *data;
    int length;

    class_zoo (nonetype) : data (nullptr), length (0) {}
    class_zoo (const T &e) : data (&e), length (1) {}
};

int bar (class_zoo<const int *> p1 = none,
         class_zoo<const unsigned *> p2 = none)
{
  if (*p1.data==nullptr) return 1;
  return 0;
}

int foo (int *b)   // If changing int to const int here, zoo will
return 0 (pass)
{
  class_zoo<const int *> zoo(b);
  return bar(zoo);
}

int g = 678;
int main ()
{
  return foo (&g);
}

$ g++  main.cpp -fstack-protector -o m
$ ./m
$ echo $?
1

Expand shows:
D.2320 = b_2(D);
  class_zoo<const int*>::class_zoo (&zoo, &D.2320);
  D.2320 ={v} {CLOBBER};    <------- D.2320 is dead, but it is address
escapes to zoo
                                           <------- with
stack-protector, D.2322 reuses stack slot of D.2320, thus overwrite
D.2320
  class_zoo<const unsigned int*>::class_zoo (&D.2322, 0);
  _8 = bar (zoo, D.2322);        <-------- D.2320 is accessed via its
address, but value changed now
  _9 = _8;
  D.2322 ={v} {CLOBBER};
  zoo ={v} {CLOBBER};
;;    succ:       3

;;   basic block 3, loop depth 0
;;    pred:       2
<L2>:
  return _9;
;;    succ:       EXIT

}


Partition 0: size 16 align 16
        D.2322  D.2320              <------- GCC believes they are not
conflict, which is what I not sure of here
Partition 2: size 16 align 16
        zoo

Questions
1. Is this a correct test case?
2. If not, why escaping of D.2320's address to a local is not
accounted as conflicting to other local variables?

Thanks,
Joey