PI58820: FLOATING POINT EXCEPTION NOT THROWN AT -O2

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• When compiling at -O2, the resulting binary does not throw a
  floating point exception at runtime. We seem to be pre-computing
   a value and then printing it out during runtime.
  
  ===== TESTCASE:
  $ cat overflow2.cpp
  #include <stdio.h>
  int main (int argc, char* argv);
  
  int main (int argc, char* argv) {
          double f = 2.82e+41;
  
          printf("f is %f\n", f); fflush(stdout);
  
          f *= f;  // Expect to get HFP exponent overflow here
  
          printf("f is %f\n", f); fflush(stdout);
  
          return 0;
  }
  
  $
  
  
  
  ===== ACTUAL OUTPUT:
  $ ./overflow2opt1
  f is 282000000000000000000000000000000000000000.000000
  f is 0.000000
  
  
  
  ===== EXPECTED OUTPUT:
  $ ./overflow2opt0
  f is 282000000000000000000000000000000000000000.000000
  CEE3212S The system detected an exponent-overflow exception
  (System Completion Code=0CC).
           From entry point main at compile unit offset +00000070
  at entry offset +00000070 at address 2540A190.
  [1] + Done(136) ./overflow2opt0
    83889146      Floating point exception        ./overflow2opt0
  
  $
  

Local fix

• N/A
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: zOS C/C++ compiler users using hexadecimal   *
  *                 floating point format in programs that may   *
  *                 trigger floating point exceptions.           *
  ****************************************************************
  * PROBLEM DESCRIPTION: Failure to generate floating point      *
  *                      overflow exception when optimization    *
  *                      is performed.                           *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  

Problem conclusion

• Apply provided service.
  

Temporary fix

Comments

APAR Information

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

  PI44210

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

Modules/Macros

•    CCNETBY
  

Fix information

• Fixed component name

  C/C++ FOR MVS

• Fixed component ID

  56551210A

Applicable component levels

• R7A0 PSY UI36029

     UP16/04/26 P F604

Fix is available

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