IJ36117: COMPILING WITH -O CAUSES INCORRECT EVALUATION OF IF STATEMENT

APAR status

• Closed as program error.

Error description

• When compiling the provided test case with -O, the following if
  statement evaluates incorrectly:
  
  if ((dir <= 0) && (((indx >= 0) && (indx < 10000)) || (indx >
  20000)))
  
  returns TRUE with dir=-1 and indx=-2
  
  
  =====COMPILE COMMAND:
  xlc_r -DBUILD_ARCH64 -qcheck=divzero -q64 -qlanglvl=extc99
  -qhssngl -qchars=signed -qmaxmem=-1 -qcpluscmt -Q -Dpower64_aix4
   -Daix4  -DSAG_COM -Dunix   -O -qalias=noansi  -o
  test_loop.exe_nodebug test_loop.c
  
  
  =====TESTCASE:
  $ cat test_loop.c
  #define       i4              int
  #define       i2              short
  #define       u_i2            unsigned short
  typedef i4      nat;
  typedef         char *          PTR;
  typedef i2 DB_DT_ID;
  #include <stdio.h>
  
  
  
  typedef struct _DB_DATA_VALUE
  {
      PTR             db_data;
      i4              db_length;
      DB_DT_ID        db_datatype;
      i2              db_prec;
      i2              db_collID;
  }   DB_DATA_VALUE;
  
  
  typedef struct _DB_DATA_VALUE   *DBVARRAY;
  
  
  typedef struct iiscopes
  {
          char  *class;
          u_i2   usecount;
          char  *clientdata;
          char  * namestr;
          i2    resolved;
          struct iiscopes *parent;
          struct iiscopes *sibling;
          i2      source;
  } IISCOPES;
  
  typedef struct _QRY
  {
          i4              qr_zero;
          i4              qr_version;
  
  # define        QR_VERSION_MASK 0xff
  # define        QR_VERSION      3
  # define        QR_0_ROWS_OK    0x100
  # define        QR_ROWS_FOUND   0x200
  
          char            *qr_argv;
          char            *qr_putparam;
          const char      *qr_form;
          const char      *qr_table;
          struct _QRY     *qr_child;
          char            *qr_qdesc;
  } QRY;
  
  
  typedef struct _abrts_ds
  {
          nat             type;
  #define ABRTS_DSTYPE_CURSOR     1
  #define ABRTS_DSTYPE_UCARRAY    2
  #define ABRTS_DSTYPE_SARRAY     3
  
          nat  num_cols;
          char * target_obj;
          char **col_targs;
          char **col_names;
          char *datacache;
  
  } ABRTS_DATASET;
  
  
  
  typedef struct _abrtspv
  {
          DB_DATA_VALUE   abpvvalue;
          char            *abpvsymbol;
          char            *abpvdtype;
          i2              abpvbrtype;
          i2              abpvindx;
          i2              abpvmem;
  } ABRTSPV;
  
  
  
  
  typedef struct _abrtsprm
  {
          ABRTSPV         *pr_actuals;
          char            **pr_formals;
          nat             pr_argcnt;
          DB_DATA_VALUE   pr_retvalue;
          i2              pr_flags;
          u_i2            pr_usecount;
          PTR             pr_extblock;
          nat             pr_dataset_cnt;
          ABRTS_DATASET   *pr_datasets;
  } ABRTSPRM;
  
  
  
  typedef struct _abrts_dc
  {
          char            *tuple_buffer;
          nat             tb_size;
          PTR             descriptor;
          struct iiobject *cache;
  } ABRTS_DATACACHE;
  
  
  
  static void iiarPassArg (ABRTSPRM *, IISCOPES *, DBVARRAY, i4,
  char *, char *);
  
  
  main()
  {
  
          ABRTSPRM prm1;
          ABRTSPV prv[3];
          IISCOPES scopes;
          DBVARRAY dbvarray;
  
          prm1.pr_argcnt = 3;
          prv[0].abpvbrtype = 45;
          prv[0].abpvindx = -2;
          prv[1].abpvbrtype = 30;
          prv[1].abpvindx = 1;
          prv[2].abpvbrtype = 30;
          prv[2].abpvindx = 1;
  
          prm1.pr_actuals= &prv[0];
  
          iiarPassArg (&prm1, &scopes,dbvarray, -1, NULL, NULL);
  }
  
  static void
  iiarPassArg (
      ABRTSPRM    *prm,
      IISCOPES    *symtab,
      DBVARRAY    dbdvarr,
      i4          dir,
      char        *obj,
      char        *kind
  )
  {
          register ABRTSPV    *ap;
          nat                 cnt;
  
          for (ap = prm->pr_actuals, cnt = 0; cnt <
  prm->pr_argcnt; ++cnt,  ++ap)
          {
                  i4      indx;
  
                  indx = (i4)(ap->abpvindx);
  
  
                  if ((dir <= 0) && (((indx >= 0) && (indx <
  10000)) || (indx > 20000)))
                  {
                          printf ("TEST 1 TRUE for loop %d\n",
  cnt);
                  }
                  else
                  {
                          printf ("TEST 1 FALSE for loop %d\n",
  cnt);
                  }
  
                  if ((dir <= 0) && (((indx >= 0) && (indx <
  10000)) || (indx > 20000)))
                  {
                          printf ("TEST 2 TRUE continue for loop
  %d\n", cnt);
                          continue;
                  }
                  else
                  {
                          printf ("TEST 2 FALSE for loop %d\n",
  cnt);
                  }
                  printf ("WE PASS HERE %d\n", cnt);
  
          }
  }
  
  $
  
  ===== ACTUAL OUTPUT:
  $ ./test_loop.exe_nodebug
  TEST 1 TRUE for loop 0
  TEST 2 TRUE continue for loop 0
  TEST 1 TRUE for loop 1
  TEST 2 TRUE continue for loop 1
  TEST 1 TRUE for loop 2
  TEST 2 TRUE continue for loop 2
  $
  
  ===== EXPECTED OUTPUT:
  $ ./test_loop.exe_nodebug
  TEST 1 FALSE for loop 0
  TEST 2 FALSE for loop 0
  WE PASS HERE 0
  TEST 1 TRUE for loop 1
  TEST 2 TRUE continue for loop 1
  TEST 1 TRUE for loop 2
  TEST 2 TRUE continue for loop 2
  $
  

Local fix

• N/A
  

Problem summary

• USERS AFFECTED:
  Users who have test cases that make use of the ternary operator
  might be affected by this issue.
  
  PROBLEM DESCRIPTION:
  The compiler was not treating the types of the two branch
  statements of the ternary operator correctly leading to
  incorrect code gen causing the incorrect output.
  

Problem conclusion

• A compiler fix has been implemented for the above mentioned
  issue.
  

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:

  IJ36457

Fix information

• Fixed component name

  XL C FOR AIX

• Fixed component ID

  5725C7100

Applicable component levels