[Bug c++/126599] [reflection] display_string_of(nullptr-pointer-to-data-member) is "-1"

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D126599

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
For
struct S { int s, t; };
template <auto M>
void foo (int);
void
bar ()
{
  foo <(int S::*)nullptr> ();
  foo <&S::s> ();
  foo <&S::t> ();
}
we diagnose
pr126599.C: In function =E2=80=98void bar()=E2=80=99:
pr126599.C:7:27: error: no matching function for call to =E2=80=98foo<-1>()=
=E2=80=99
    7 |   foo <(int S::*)nullptr> ();
      |   ~~~~~~~~~~~~~~~~~~~~~~~~^~
  =E2=80=A2 there is 1 candidate
    =E2=80=A2 candidate 1: =E2=80=98template<auto M> void foo(int)=E2=80=99
      pr126599.C:3:6:
          3 | void foo (int);
            |      ^~~
      =E2=80=A2 candidate expects 1 argument, 0 provided
pr126599.C:8:15: error: no matching function for call to =E2=80=98foo<&S::s=
>()=E2=80=99
    8 |   foo <&S::s> ();
      |   ~~~~~~~~~~~~^~
  =E2=80=A2 there is 1 candidate
    =E2=80=A2 candidate 1: =E2=80=98template<auto M> void foo(int)=E2=80=99
      pr126599.C:3:6:
          3 | void foo (int);
            |      ^~~
      =E2=80=A2 candidate expects 1 argument, 0 provided
pr126599.C:9:15: error: no matching function for call to =E2=80=98foo<&S::t=
>()=E2=80=99
    9 |   foo <&S::t> ();
      |   ~~~~~~~~~~~~^~
  =E2=80=A2 there is 1 candidate
    =E2=80=A2 candidate 1: =E2=80=98template<auto M> void foo(int)=E2=80=99
      pr126599.C:3:6:
          3 | void foo (int);
            |      ^~~
      =E2=80=A2 candidate expects 1 argument, 0 provided
&S::s and &S::t is printed for PTRMEM_CST, while -1 is printed for OFFSET_T=
YPE
INTEGER_CST:
216           /* A NULL pointer-to-data-member is represented by -1, not by
217              zero.  */
218           tree val =3D (TYPE_PTRDATAMEM_P (type)
219                       ? build_int_cst_type (type, -1)
220                       : build_int_cst (type, 0));=