IV91259: INLINING CAUSING INCORRECT RESULT IN ARRAY INITIALIZATION WITH CONSTRUCTED ELEMENT

XL C/C++ for AIX Fix Pack 18 (February 2017 Update) for 12.1
XL C/C++ for AIX Fix Pack 19 (August 2017 Update) for 12.1
XL C/C++ for AIX Fix Pack 20 (March 2018 Update) for 12.1
XL C/C++ for AIX Fix Pack 21 (January 2019 Update) for 12.1

APAR status

• Closed as program error.

Error description

• Incorrect storage to a struct member is seen when an operator-
  is inlined.  The store offset into the struct is incorrect when
  using an array initialization with constructed elements.  In the
  example below:
  
    T v[1] = { { 7, d - 2 } };  // THE STORAGE OF THE 'd - 2'
                                // RESULT INTO THE NEW D OBJECT
                                // HAS WRONG OFFSET
  
  
     === TEST CASE ===
  #include <stdio.h>
  
  struct D
  {
      int d;
      D(int s) : d(s) { printf("D(%d)\n",s); }
  };
  
  inline D operator-(const D &d, int n)
  {
      printf("D op-(%d,%d)=%d\n",d.d,n,d.d-n);
      return D(d.d - n);
  }
  
  struct T
  {
   int v;
   D d;
  };
  
  void verify(const T &t)
  {
      printf("t={%d,{%d}} : ", t.v, t.d.d);
      printf("%s\n", t.v == 7 && t.d.d==3 ? "Good" : "Bad");
  }
  
  int main()
  {
      D d(5);
      T v[1] = { { 7, d - 2 } };
      verify(v[0]);
  }
  
  
  
  $ xlC -qinline test.cpp
  $ ./a.out
  D(5)
  D op-(5,2)=3
  D(3)
  t={3,{146}} : Bad
  $
  

Local fix

• - Do not use -qinline
  - Prevent inlining via the __attribute__ ((noinline)) function
  attribute
  

Problem summary

• USERS AFFECTED:
  The problem may be exposed when an array of class type is
  initialized with a
  bracelist initializer when the constructor call for a member of
  the class is inlined.
  
  PROBLEM DESCRIPTION:
  The inlined code exposed a problem with code generation that
  incorrectly
  specified indexes and offsets for the array members.
  

Problem conclusion

• The problem has been resolved.
  

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:

  IV95477 IV97596

Fix information

• Fixed component name

  XL C/C++ FOR AI

• Fixed component ID

  5725C7200

Applicable component levels