IZ89322: TRAPS WITH -QFLTTRAP=IMP -O3 -QSTRICT

January 2011 PTF for XL C/C++ for AIX, V11.1
May 2011 PTF for XL C for AIX, V11.1
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January 2012 PTF for XL C for AIX, V11.1
January 2012 PTF for XL C/C++ for AIX, V11.1
April 2012 PTF for XL C for AIX, V11.1
April 2012 PTF for XL C/C++ for AIX, V11.1
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February 2013 PTF for XL C for AIX, V11.1
February 2013 PTF for XL C/C++ for AIX, V11.1
XL C/C++ for AIX Fix Pack 14 (May 2013 PTF) for 11.1
XL C for AIX Fix Pack 14 (May 2013 PTF) for 11.1
XL C/C++ for AIX Fix Pack 15 (August 2013 PTF) for 11.1
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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 for AIX Fix Pack 21 (April 2015 PTF) for 11.1
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XL C/C++ for AIX Fix Pack 22 (September 2015 PTF) for 11.1
XL C for AIX Fix Pack 23 (March 2016 PTF) for 11.1
XL C/C++ for AIX Fix Pack 23 (March 2016 PTF) for 11.1
XL C for AIX Fix Pack 24 (September 2016 PTF) for 11.1
XL C/C++ for AIX Fix Pack 24 (September 2016 PTF) for 11.1
January 2011 PTF for XL C for AIX, V11.1
August 2011 PTF for XL C for AIX, V11.1
November 2011 PTF for XL C for AIX, V11.1
July 2012 PTF for XL C for AIX, V11.1
XL C for AIX Fix Pack 16 (November 2013 PTF) for 11.1
XL C for AIX Fix Pack 18 (May 2014 PTF) for 11.1
XL C for AIX Fix Pack 19 (August 2014 PTF) for 11.1
XL C for AIX Fix Pack 20 (November 2014 PTF) for 11.1
XL C for AIX Fix Pack 22 (September 2015 PTF) for 11.1

APAR status

• Closed as program error.

Error description

• The following test case traps if compiled with -O3 -qflttrap=imp
  -qstrict
  
  xlc -O3 -qflttrap=imp -qstrict fltint.c && ./a.out
  i 0  c '0'
  Trace/BPT trap
  
  
  -----
  $cat fltint.c
  
  #include <stdio.h>
  #include <fptrap.h>
  
  void foo(int val, int *dst)
  {
    int i;
  
    for (i = 0; i < 1; i++)
      *dst = val;
  }
  
  int zero;
  
  void bar(char *fmt)
  {
    int rc, i, c, t;
    double x;
  
    rc = 0 ;
    x = zero ? 0 : 1e100;
  
    for (i = 0; i < 1 && rc == 0; i++)
    {
      c = fmt[0];
      printf("i %d  c '%c'\n", i, c);
      switch (c)
      {
      case 'A':                  break;
      case 'B': foo((int)x, &t); break;
      default:           rc = 1; break;
      }
    }
  }
  
  int main()
  {
    (void) fp_enable(TRP_INVALID);
    bar("0");
    return 0;
  }
  

Local fix

• Use -qflttrap instead of -qflttrap=imp
  

Problem summary

• PROBLEM DESCRIPTION: A potentially trapping floating point
  instruction could be moved past a guarding branch
  
  USERS AFFECTED: Users of -qflttrap or those enabling floating
  point traps via AIX function calls
  

Problem conclusion

• Two additional flags now suppress moving potentially trapping
  instructions past branches.
  With the fix, users can use -qfloat=fenv or -qstrict=guards to
  guard the condition.
  
  For example, compile with xlc -O3 -qflttrap=imp -qfloat=fenv or
  xlc -O3 -qflttrap=imp -qstrict=guards.
  

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:

  LI76109

Fix information

• Fixed component name

  XL C FOR AIX

• Fixed component ID

  5724X1200

Applicable component levels