IJ08181: INCORRECT EVALUATION OF DEFAULT TEMPLATE PARAMETER

XL C/C++ for AIX, V13.1.3.5 Fix Pack (July 2018)
XL C/C++ for AIX, V13.1.3.6 Fix Pack (May 2019)

APAR status

• Closed as program error.

Error description

• A template default parameter is not found by the compiler.  The
  default parameter is dependant on the first template type in the
  template parameter list, which is itself a typedef.
  
  
     === TEST CASE ===
  
  template <class LIST,
            int NUMBER = LIST::LENGTH>
  struct TypeListTypeOf {
      typedef int Type;
  };
  
  template <typename A1>
  struct TypeList {
      enum { LENGTH = 1 };
  };
  
  typedef TypeList<double> List;
  
  template <typename ARG>
  struct OffsetOf {
      typedef TypeListTypeOf<List>::Type Type;
         // 'List'is a TypeList, containing the LENGTH declaration
  };
  
  int main()
  {
      OffsetOf<int>::Type foo = 0;
  
      (void) foo;
  }
  
  
  $ xlC -c apar.cpp
  "apar.cpp", line 2.24: 1540-0130 (S) "LENGTH" is not declared.
  $
  

Local fix

Problem summary

• PROBLEM DESCRIPTION:
  An incorrect instantiation point causes the compiler to miss an
  implicit instantiation required to compile resulting in an
  error for an invalid use of an incomplete class.
  
  USERS AFFECTED:
  The problem happens with the use of a default template
  parameter in a template class.
  

Problem conclusion

• The problem has been resolved.
  

Temporary fix

Comments

APAR Information

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

  IV99406

• 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

• RD13 PSN IV99406

     UP06/09/13