checking malloc

gistfile1.txt

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

void checkzero(char *p, int size) {
  while(--size) {
    if(p[size]) {
      printf("%p is non-zero at offset %d, the value is 0x%02hhx\n", 
             p, size, p[size]);
      return;
    }
  }
  printf("%p is zero in all %d bytes\n", p, size);
}

void do_round() {
  char *ptr;
  ptr = malloc(1024);
  checkzero(ptr, 1024);
  memset(ptr, 0xff, 1024);
  free(ptr);
}

int main(int argc, char *argv[]) {
  do_round();
  do_round();
  do_round();
}


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$ ./a.out 
0x1ed3010 is zero in all 0 bytes
0x1ed3010 is non-zero at offset 1023, the value is 0xff
0x1ed3010 is non-zero at offset 1023, the value is 0xff