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Subject: [Bug c++/55962] improper location for static_assert
Date: Sun, 13 Jan 2013 19:17:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D55962

Manuel L=C3=B3pez-Ib=C3=A1=C3=B1ez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-01-13
                 CC|                            |manu at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #1 from Manuel L=C3=B3pez-Ib=C3=A1=C3=B1ez <manu at gcc dot gnu=
.org> 2013-01-13 19:17:05 UTC ---
Confirmed. If you run GCC under GDB, you'll notice that the call=20

  if (expr =3D=3D error_mark_node || TREE_CODE (expr) =3D=3D TREE_LIST)
    {
      if (complain & tf_error)
        qualified_name_lookup_error (scope,
                                     TREE_OPERAND (qualified_id, 1),
=3D>                                   expr, input_location);
      return error_mark_node;
    }


uses input_location. I think it should use an explicit location. The proble=
m is
how to get the location of 'value' to this point.=20

Up one-level input_location is "hacked" to be=20

 loc =3D input_location;
  if (EXPR_HAS_LOCATION (t))
    input_location =3D EXPR_LOCATION (t);

but in this case t is just:

 <scope_ref 0x7ffff753e640 tree_0
    arg 0 <template_type_parm 0x7ffff75439d8 T type_0 type_6 VOID
        align 8 symtab 0 alias set -1 canonical type 0x7ffff75439d8
       index 0 level 1 orig_level 1
        chain <type_decl 0x7ffff753f958 T>>
    arg 1 <identifier_node 0x7ffff7552d10 value
        bindings <(nil)>
        local bindings <(nil)>>>

so it doesn't have a location, so it uses input_location.

The issue seems to be that input_location has somehow been smashed by somet=
hing
else. For the testcase:

void assert(int, const char *);
template <typename T>
int
foo(int b)
{
  assert(T::value, "toto");
  return b;
}

int
main()
{
  foo<int>(12);
}


we get:

test.cc:6:26: error: =E2=80=98value=E2=80=99 is not a member of =E2=80=98in=
t=E2=80=99
   assert(T::value, "toto");
                          ^
which is slightly better and the only difference seems to be the value of
input_location in the condition above.

This requires much more investigation.