test/alias3.c

   1 /*
   2 ** tests aliasing of arrays, structs and unions
   3 */
   4
   5 # include "alias3.lh"
   6
   7 st gst;
   8 ut *gu;
   9
  10 void model (int ia[])
  11 {
  12   int *ip;
  13
  14   ip = &(ia[6]);
  15   *ip = 3;
  16   gst.a = 3; /* 1. Suspect modification of gst.a */
  17   gu->a = 5; /* 2. Suspect modification of gu->a */
  18 }
  19
  20 void modst (st s1)
  21 {
  22   s1.a = 3;
  23   *(s1.b) = 6;
  24 }
  25
  26 void modu (ut *u)
  27 {
  28   u->a = 5;
  29 }
  30
  31 int f (int ia[], st s1, ut *u1)
  32 {
  33   int *ip;
  34   st   sl;
  35   ut   *ul;
  36
  37   ip = &(ia[3]);
  38   *ip = 7; /* modifies ia[3] */
  39
  40   ip = &(ia[*ip]);
  41
  42   *ip = 8; /* modifies ia[?] */
  43
  44   model(ia); /* modifies ia[6] */
  45   ip = ia;
  46   model(ip); /* modifies ia[6] */
  47
  48   s1.a = 3;    /* okay */
  49   *(s1.b) = 7; /* modifies *(s1.b) */
  50
  51   sl = s1;     /* okay (sl is NOT an alias for s1) */
  52   modst(sl);   /* was: does not modify anything --- structure is passed by value */
  53                /* NOT TRUE: does modify sl since *s1.b is the same reference */
  54   sl.a = 3;    /* okay */
  55   ip = s1.b;   /* okay, ip aliases s1.b */
  56   *(s1.b) = 3; /* modifies s1.b */
  57   *ip = 6;     /* modifies s1.b */
  58   *(sl.b) = 3; /* okay */
  59
  60   ul = u1;     /* ul aliases u1 */
  61   modu(ul);    /* okay */
  62   ul->a = 3;   /* modifies u1->a */
  63   sl = ul->s;  /* okay */
  64   sl.a = 3;    /* okay */
  65   *(sl.b) = 6; /* modifies *(u1->s.b) through alias */
  66   return 5;
  67 }