IV39827: STD::PAIR OBJECT GIVING BAD OUTPUT WITH OPT

XL C/C++ for AIX Fix Pack 15 (August 2013 PTF) for 11.1
XL C/C++ for AIX Fix Pack 16 (November 2013 PTF) for 11.1
XL C/C++ for AIX Fix Pack 17 (February 2014 PTF) for 11.1
XL C/C++ for AIX Fix Pack 18 (May 2014 PTF) for 11.1
XL C/C++ for AIX Fix Pack 19 (August 2014 PTF) for 11.1
XL C/C++ for AIX Fix Pack 20 (November 2014 PTF) for 11.1
XL C/C++ for AIX Fix Pack 21 (April 2015 PTF) for 11.1
XL C/C++ for AIX Fix Pack 22 (September 2015 PTF) for 11.1
XL C/C++ for AIX Fix Pack 23 (March 2016 PTF) for 11.1
XL C/C++ for AIX Fix Pack 24 (September 2016 PTF) for 11.1

APAR status

• Closed as program error.

Error description

• After enabling optimization on code that creates std::pair<>
  objects created using NULL pointers, object initialization code
  is optimized away and incorrect output is seen.
  
  
      ==== TEST CASE ====
  
  #include <utility>
  #include <iostream>
  
  class Test;
  
  void g()
  {
      std::pair<int, Test*> tab[3] = {
          std::make_pair(1, (Test*)NULL),
          std::make_pair(1, (Test*)NULL),
          std::make_pair(1, (Test*)NULL)
      };
  
       std::cout   << tab[0].first << '\n';
       std::cout   << tab[0].second << '\n';
       std::cout   << tab[1].first << '\n';
       std::cout   << tab[1].second << '\n';
       std::cout   << tab[2].first << '\n';
       std::cout   << tab[2].second << '\n';
  }
  
  int main()
  {
      g();
  }
  
  
  $ xlC -q64 -O2 test.cpp
  $ ./a.out
  1
  0
  1157627904
  800200140000400
  150994943
  0
  $
  

Local fix

• Do no use optimization.
  

Problem summary

• PROBLEM DESCRIPTION:
  Brace list array initialization is giving insufficient aliasing
  information to ensure program correctness.
  
  USERS AFFECTED:
  Runtime brace lists initializing an array of an aggregate type,
  compiled with optimization.
  

Problem conclusion

• The aliasing issue was resolved, and correct behaviour is now
  given.
  

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++ AIX

• Fixed component ID

  5724X1300

Applicable component levels

• RB10 PSY U860996

     UP C