IV31755: -Q64 AND -QLONGLIT CAUSES INCORRECT OUTPUT

November 2012 PTF for XL C for AIX, V12.1
November 2012 PTF for XL C/C++ for AIX, V12.1
March 2013 PTF for XL C for AIX, V12.1
March 2013 PTF for XL C/C++ for AIX, V12.1

APAR status

• Closed as program error.

Error description

• Compiler incorrectly issues warning message and resulting
  binary outputs incorrect result.
  
  The following test case demonstrates the problem:
  
  $cat longtest.c
  /////////////// longtest.c ////////////////
  
  #include <stdio.h>
  #pragma pack (1)
  
  struct testst{
    char   a;
    int    b;
    char   c;
    double d;
    float  e;
  };
  
  int main() {
    struct testst st;
    unsigned long l_buff;
    l_buff = 1000000 * 2185;
    printf("%ld,0x%016lX\n", l_buff, l_buff);
    printf("%d\n", sizeof(st));
    printf("%ld\n", (long)&(st.b) - (long)&st);
    printf("%ld\n", (long)&(st.c) - (long)&(st.b));
    printf("%ld\n", (long)&(st.d) - (long)&(st.c));
    printf("%ld\n", (long)&(st.e) - (long)&(st.d));
    exit(0);
  }
  
  #pragma pack ()
  
  /////////// end of longtest.c /////////////
  
  
  Compile command:
  
  xlc -q64 -qlonglit longtest.c
  "longtest.c", line 2.15: 1506-363 (W) Packing boundary must be
  specified as one of 1, 2, 4, 8 or 16.
  "longtest.c", line 2.1: 1506-224 (W) Incorrect pragma ignored.
  "longtest.c", line 25.15: 1506-726 (W) Attempting to pop an
  empty pack stack. Current pack may change.
  
  
  
  Wrong output before applying the PTF:
  
  ./a.out
  2185000000,0x00000000823C7440
  24
  4
  4
  4
  8
  
  
  Correct output after applying the PTF:
  
  ./a.out
  2185000000,0x00000000823C7440
  18
  1
  4
  1
  8
  

Local fix

• N/A
  

Problem summary

• Compiler incorrectly emits message: 1506-363 (W) Packing
  boundary must be specified as one of 1, 2, 4, 8 or 16.
  

Problem conclusion

• The problem is resolved by adjusting the length to 64 bits when
  processing 64 bit long literals.
  

Temporary fix

Comments

APAR Information

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

  IV26832

• 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

• RC10 PSN U856101

     UP06/09/13 C