memcheck/tests/realloc3.c

   1 /* For a long time (from Valgrind 1.0 to 1.9.6, AFAICT) when realloc() was
   2    called and made a block smaller, or didn't change its size, the
   3    ExeContext of the block was not updated;  therefore any errors that
   4    referred to it would state that it was allocated not by the realloc(),
   5    but by the previous malloc() or whatever.  While this is true in one
   6    sense, it is misleading and not what you'd expect.  This test
   7    demonstrates this -- 'x' and 'y' are unchanged and shrunk, and their
   8    ExeContexts should be updated upon their realloc().  I hope that's clear.
   9 */
  10 #include <stdlib.h>
  11
  12 int main(void)
  13 {
  14    int* x = malloc(5);
  15    int* y = malloc(10);
  16    int* z = malloc(2);
  17    int a, b, c;
  18
  19    x = realloc(x, 5);   // same size
  20    y = realloc(y, 5);   // make smaller
  21    z = realloc(z, 5);   // make bigger
  22
  23    a = (x[5] == 0xdeadbeef ? 1 : 0);
  24    b = (y[5] == 0xdeadbeef ? 1 : 0);
  25    c = (z[5] == 0xdeadbeef ? 1 : 0);
  26
  27    return a + b + c;
  28 }