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carraysmallocrealloc

Using realloc to increase the size of an array

I am trying to scan a bunch of characters into an array. I have used malloc to set the original size of the array, but I want to use realloc to increase the size if the user enters more characters than the initial size allows. I am not quite sure where to put the realloc, or if it should be within a conditional statement.

char *strscan(void) {
  int size = sizeof(char) * 10;
  char *a = malloc(size);

  // Below I try to read character input from the user and store it in the array.

 while (a != EOF) {

    scanf("%c", a);
    if (trace) printf("%c", *a);
    ++a;
    a = realloc(a, 2 * size);
 }

    return a;

}

As of now I still get heap buffer overflow upon entering, for example, 15 characters.

Solution 
  • ++a;
a = realloc(a, 2 * size);

    This is the problem. The first argument of realloc must be a pointer that is returned by the malloc family functions, or a null pointer. a used to be one, but by ++a;, it's not any more.