[Bug c++/102378] missing -Waddress in template code at definition time rather than instantiation

["msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102378

--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
With the correct explicit instantiation directive things look much better:

$ cat pr102378.C && gcc -S -Wall pr102378.C
int f ()
{
  int a[2];
  return &a == 0;      // -Waddress (good)
}

template <class T>
int g ()
{
  {
    int a[2];
    return &a == 0;    // missing -Waddress
  }

  {
    T t;
    return &t == 0;    // no -Waddress for type-dependent expr (good)
  }

  {
    T a[2];
    return &a == 0;    // missing -Waddress
  }
}

template <class T>
int h ()
{
  {
    int a[2];
    return &a == 0;    // -Waddress (good)
  }

  {
    T t;
    return &t == 0;    // -Waddress (good)
  }

  {
    T a[2];
    return &a == 0;    // -Waddress (good)
  }
}

template int h<int> ();
pr102378.C: In function ‘int f()’:
pr102378.C:4:13: warning: the address of ‘a’ will never be NULL [-Waddress]
    4 |   return &a == 0;      // -Waddress (good)
      |          ~~~^~~~
pr102378.C: In instantiation of ‘int h() [with T = int]’:
pr102378.C:45:22:   required from here
pr102378.C:31:15: warning: the address of ‘a’ will never be NULL [-Waddress]
   31 |     return &a == 0;    // -Waddress (good)
      |            ~~~^~~~
pr102378.C:36:15: warning: the address of ‘t’ will never be NULL [-Waddress]
   36 |     return &t == 0;    // -Waddress (good)
      |            ~~~^~~~
pr102378.C:41:15: warning: the address of ‘a’ will never be NULL [-Waddress]
   41 |     return &a == 0;    // -Waddress (good)
      |            ~~~^~~~