memcheck/tests/overlap.c

   1 #include <string.h>
   2 #include <stdio.h>
   3
   4 char b[50];
   5
   6 void reset_b(void)
   7 {
   8    int i;
   9
  10    for (i = 0; i < 50; i++)
  11       b[i] = '_';
  12    b[49] = '\0';
  13 }
  14
  15 void reset_b2(void)
  16 {
  17    reset_b();
  18    strcpy(b, "ABCDEFG");
  19 }
  20
  21 int main(void)
  22 {
  23    char x[100];
  24    char a[] = "abcdefghijklmnopqrstuvwxyz";
  25    int  i;
  26
  27    /* testing memcpy/strcpy overlap */
  28
  29    for (i = 0; i < 50; i++) {
  30       x[i] = i+1;    // don't put any zeroes in there
  31    }
  32    for (i = 50; i < 100; i++) {
  33       // because of the errors, the strcpy's will overrun, so put some
  34       // zeroes in the second half to stop them eventually
  35       x[i] = 0;
  36
  37    }
  38
  39    memcpy(x+20, x, 20);    // ok
  40    memcpy(x+20, x, 21);    // overlap
  41    memcpy(x, x+20, 20);    // ok
  42    memcpy(x, x+20, 21);    // overlap
  43
  44    strncpy(x+20, x, 20);    // ok
  45    strncpy(x+20, x, 21);    // overlap
  46    strncpy(x, x+20, 20);    // ok
  47    strncpy(x, x+20, 21);    // overlap
  48
  49    x[39] = '\0';
  50    strcpy(x, x+20);    // ok
  51
  52    x[39] = 39;
  53    x[40] = '\0';
  54    strcpy(x, x+20);    // overlap
  55
  56    x[19] = '\0';
  57    strcpy(x+20, x);    // ok
  58
  59 /*
  60    x[19] = 19;
  61    x[20] = '\0';
  62    strcpy(x+20, x);    // overlap, but runs forever (or until it seg faults)
  63 */
  64
  65    /* testing strcpy, strncpy() */
  66
  67    reset_b();
  68    printf("`%s'\n", b);
  69
  70    strcpy(b, a);
  71    printf("`%s'\n", b);
  72
  73    reset_b();
  74    strncpy(b, a, 25);
  75    printf("`%s'\n", b);
  76
  77    reset_b();
  78    strncpy(b, a, 26);
  79    printf("`%s'\n", b);
  80
  81    reset_b();
  82    strncpy(b, a, 27);
  83    printf("`%s'\n", b);
  84
  85    printf("\n");
  86
  87    /* testing strncat() */
  88
  89    reset_b2();
  90    printf("`%s'\n", b);
  91
  92    reset_b2();
  93    strcat(b, a);
  94    printf("`%s'\n", b);
  95
  96    reset_b2();
  97    strncat(b, a, 25);
  98    printf("`%s'\n", b);
  99
 100    reset_b2();
 101    strncat(b, a, 26);
 102    printf("`%s'\n", b);
 103
 104    reset_b2();
 105    strncat(b, a, 27);
 106    printf("`%s'\n", b);
 107
 108    /* Nb: can't actually get strcat warning -- if any overlap occurs, it will
 109       always run forever, I think... */
 110
 111    for ( i = 0; i < 2; i++)
 112       strncat(a+20, a, 21);    // run twice to check 2nd error isn't shown
 113    strncat(a, a+20, 21);
 114
 115    /* This is ok, but once gave a warning when strncpy() was wrong,
 116       and used 'n' for the length, even when the src was shorter than 'n' */
 117    {
 118       char dest[64];
 119       char src [16];
 120       strcpy( src, "short" );
 121       strncpy( dest, src, 20 );
 122    }
 123
 124    return 0;
 125 }