LI75138: CODE WITH INCORRECT TEMPLATE INSTANTIATION

October 2009 Update for XL C/C++ for Linux, V10.1
June 2011 Update for XL C/C++ for Linux, V10.1
XL C/C++ for Linux Fix Pack 8 (January 2014 Update) for 10.1
August 2010 Update for XL C/C++ for Linux, V10.1
January 2011 Update for XL C/C++ for Linux, V10.1
January 2012 Update for XL C/C++ for Linux, V10.1
July 2012 Update for XL C/C++ for Linux, V10.1

APAR status

• Closed as program error.

Error description

• The following test case picks up the incorrect template
  instantiation resulting in an incorrect output at runtime.
  
  ===== COMPILE COMMAND:
  xlC_r ntest.cpp
  
  ===== TESTCASE:
  $cat ntest.cpp
  #include <iostream>
  
  template <class FUNC>
  struct hasEllipsis
  {
      enum {VALUE = 0};
  };
  
  template <class RET>
  struct hasEllipsis<RET (*)(...)>
  {
      enum {VALUE = 1};
  };
  
  template <class RET, class A1>
  struct hasEllipsis<RET (*)(A1,...)>
  {
      enum {VALUE = 2};
  };
  
  template <class RET, class A1, class A2>
  struct hasEllipsis<RET (*)(A1,A2,...)>
  {
      enum {VALUE = 3};
  };
  
  template <class RET, class A1, class A2, class A3>
  struct hasEllipsis<RET (*)(A1,A2,A3,...)>
  {
      enum {VALUE = 4};
  };
  
  void foo(int a) {
      std::cout << "foo" << std::endl;
  }
  
  void bar(int a, ...) {
      std::cout << "bar" << std::endl;
  }
  
  template<class FUNC>
  void check(FUNC f) {
      std::cout << "\tcheck: " << hasEllipsis<FUNC>::VALUE <<
  std::endl;
  }
  
  int main()
  {
      std::cout << "foo: should print 0" << std::endl;
      // Should print 0 since the signature of 'foo' doesn't have
  an ellipsis.
      check(&foo);  // prints '2' instead
  
      std::cout << "bar: should print 2" << std::endl;
      // Should print 2 since the signature of 'bar' does have an
  ellipsis.
      check(&bar);  // correctly prints '2'.
  
      return 0;
  }
  
  
  ===== ACTUAL OUTPUT:
  $ ./a.out
  foo: should print 0
          check: 2
  bar: should print 2
          check: 2
  $
  
  
  ===== EXPECTED OUTPUT:
  $ ./a.out
  foo: should print 0
          check: 0
  bar: should print 2
          check: 2
  $
  

Local fix

• n/a
  

Problem summary

• This problem happens when there is a partial specialization
  based on a function type where 1 parameter is an ellipsis
  
  The compiler was allowing the specialization to match a
  function with no ellipsis and picking an incorrect partial
  specialization
  

Problem conclusion

• A problem in argument deduction was fixed to allow
  proper partial specialization matching with
  ellipsis in function type.
  

Temporary fix

Comments

APAR Information

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

  IZ55763

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

Fix information

• Fixed component name

  XL C/C++ SLES10

• Fixed component ID

  5724U8300

Applicable component levels

• RA10 PSN IZ55763

     UP06/09/13