IV86811: -QCHECK=UNSET CAUSING UNNECESSARY TRAP

XL C for AIX, V13.1.3.3 Fix Pack (December 2016)
XL C/C++ for AIX, V13.1.3.3 Fix Pack (December 2016)
XL C for AIX, V13.1.3.4 Fix Pack (April 2017)
XL C/C++ for AIX, V13.1.3.4 Fix Pack (April 2017)
XL C for AIX, V13.1.3.5 Fix Pack (July 2018)
XL C/C++ for AIX, V13.1.3.5 Fix Pack (July 2018)
XL C for AIX, V13.1.3.6 Fix Pack (May 2019)
XL C/C++ for AIX, V13.1.3.6 Fix Pack (May 2019)

APAR status

• Closed as program error.

Error description

• The -qcheck=unset option is incorrectly issuing a trap for the
  code below:
  
  ===== COMPILE COMMAND:
  xlC -qcheck=unset test.cpp
  
  ===== TESTCASE:
  $ cat test.cpp
  #include <map>
  
  int main(int, const char*[])
  {
      std::map<int, int> map;
      map[1] = 2;
      map.erase(1);
      return 0;
  }
  $
  
  ===== ACTUAL OUTPUT:
  $ dbx a.out
  Type 'help' for help.
  reading symbolic information ...warning: no source compiled with
  -g
  
  (dbx) run
  
  Trace/BPT trap in std::bidirectional_iterator_tag
  std::_Iter_cat<std::_Tree<std::_Tmap_traits<int,int,std::less<in
  t>,std::allocator<std::pair<const int,int> >,0>
  >::iterator>(const
  std::_Tree<std::_Tmap_traits<int,int,std::less<int>,std::allocat
  or<std::pair<const int,int> >,0> >::iterator&) at 0x10006684
  0x10006684 (std::bidirectional_iterator_tag
  std::_Iter_cat<std::_Tree<std::_Tmap_traits<int,int,std::less<in
  t>,std::allocator<std::pair<const int,int> >,0>
  >::iterator>(const
  std::_Tree<std::_Tmap_traits<int,int,std::less<int>,std::allocat
  or<std::pair<const int,int> >,0> >::iterator&)+0x24) 0c830000
  tweqi   r3,0x0
  (dbx) where
  std::bidirectional_iterator_tag
  std::_Iter_cat<std::_Tree<std::_Tmap_traits<int,int,std::less<in
  t>,std::allocator<std::pair<const int,int> >,0>
  >::iterator>(const
  std::_Tree<std::_Tmap_traits<int,int,std::less<int>,std::allocat
  or<std::pair<const int,int> >,0> >::iterator&)(0x2ff224c0,
  0x2ff224e8) at 0x10006684
  void
  std::_Distance<std::_Tree<std::_Tmap_traits<int,int,std::less<in
  t>,std::allocator<std::pair<const int,int> >,0>
  >::iterator,unsigned
  long>(std::_Tree<std::_Tmap_traits<int,int,std::less<int>,std::a
  llocator<std::pair<int,int> >,0>
  >::iterator,std::_Tree<std::_Tmap_traits<int,int,std::less<int>,
  std::allocator<std::pair<int,int> >,0> >::iterator,unsigned
  long&)(0x20002d50, 0x20002d10, 0x2ff22518) at 0x100069a8
  std::_Tree<std::_Tmap_traits<int,int,std::less<int>,std::allocat
  or<std::pair<const int,int> >,0> >::erase(const
  int&)(0x2ff22570, 0x2ff22580) at 0x10006b3c
  main(0x1, 0x2ff22610) at 0x10008538
  (dbx)
  
  
  
  ===== EXPECTED OUTPUT:
  Should run to completion without a trap
  

Local fix

• N/A
  

Problem summary

• USERS AFFECTED:
  Uses of the -qcheck=unset option with empty
  structs or with objects that make use of empty structs.
  
  PROBLEM DESCRIPTION:
  The -qcheck=unset option checks for automatic variables that
  are used
  before they are set. In the case of empty structs they cannot
  be
  initialized and therefore should not be checked by this option.
  

Problem conclusion

• Empty structs are a particular corner case that confuses the
  -qcheck=unset option.
  Since empty structs cannot be initialized the option should not
  apply to them.
  

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 FOR AIX

• Fixed component ID

  5725C7100

Applicable component levels