IJ27833: USING STATEMENT CAUSING AMBIGUOUS REFERENCE BECAUSE OF MULTIPLE ACCESS PATHS TO BASE CLASS ERROR

APAR status

• Closed as program error.

Error description

• Two function methods in the same class have the same name,
  'get', but different signatures.  A child class tries to
  access one of them and uses a 'using' statement, but the
  compiler issues an error:
  
  $ xlC -c apar.cpp
  "apar.cpp", line 33.12: 1540-0602 (S) The reference to
  "my_namespace::MyClass::get<int>(const char *) const" is
  ambiguous because "my_namespace::MyClass::get<int>(const char *)
   const" can be accessed via multiple paths to base class
   "my_namespace::MyClass".
  $
  
  
     === TEST CASE ===
  
  namespace my_namespace {
  
  class MyClass {
  public:
      virtual ~MyClass();
      virtual int id() const = 0;
  
      template<typename T>
      T get(const char *parm1) const;
  
      virtual void get(const char *parm1, int* parm2) const;
  };
  
  template<typename T>
  T MyClass::get(const char *parm1) const
  {
      T val;
      get(parm1, &val);
      return val;
  }
  
  }
  
  class MyClass : public my_namespace::MyClass
  {
  public:
      virtual int num() const ;
      using my_namespace::MyClass::get;
  };
  
  int MyClass::num() const
  {
      return get<int>("TEST");
  }
  

Local fix

• Rename duplicate function method names
  

Problem summary

• PROBLEM DESCRIPTION:
  During processing of the derived class, the 'using' declaration
  is unwound to the function template get() in the base class.
  The unwound declaration is then added to the function candidate
  list and becomes the overload resolution winner.
  When the compiler later performs error diagnostic tests, the
  invalid error is output because the compiler falsely assumes the
  enclosing class of the winner would be the derived class,
  while in actuality it is the base class.
  
  USERS AFFECTED:
  This problem affects code that has 'using' declarations in a
  derived class that introduces function templates in the related
  base class.
  

Problem conclusion

• The compiler has been fixed to handle the above scenario.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  XL C/C++ FOR AI

• Fixed component ID

  5725C7200

Applicable component levels