IJ34806: -QCHECK=UNSET NOT WORKING FOR STRUCT BITFIELDS

APAR status

• Closed as program error.

Error description

• When using the -qcheck=unset compile option with source code
  using struct bitfields, an invalid runtime trap exception is
  thrown, incorrectly implying a use-before-set code scenario.
  
  
  
     === TEST CASE ===
  
  #include <stdio.h>
  
  struct myStruct {
    unsigned value : 16;
  };
  
  int main()
  {
      struct myStruct init;
  
      init.value = 2019;
      printf("init.value=%u\n", init.value);
  
      return 0;
  }
  
  
  $ xlc apar.c   -qcheck=unset
  $ ./a.out
  Trace/BPT trap (core dumped)
  $
  

Local fix

• Do not use -qcheck=unset
  

Problem summary

• PROBLEM DESCRIPTION:
  Invalid check is done for bitfield containers in a struct.
  
  USERS AFFECTED:
  Builds using -qcheck=unset with source code containing bitfields
  

Problem conclusion

• Invalid check was removed.
  

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++ FOR AI

• Fixed component ID

  5725C7200

Applicable component levels