Thread: seg fault in vector delete function

So, here's the deal. Before you paste in your code, type "[code]". Then, after the code is all in there, type "[/code]". Learn it, live it.

If calling vfree gives you a segfault, why wouldn't you expect the problem to be in vfree? (Which is still probably trying to free a pointer that wasn't malloced.)

here is the code for vfree (it is being called on to pointers to strings (char*'s, dynamically allocated):

Code:

/** 
 * Function: FreeString
 * --------------------
 * Understands how to free a C-string.  This
 * function should be used by all vectors that
 * store char *'s (but only when those char *s
 * point to dynamically allocated memory, as
 * they do with strings.)
 */

static void FreeString(void *elemAddr)
{
  char *s = *(char **) elemAddr;
  free(s); 
}

/** 
 * Function: PrintString
 * ---------------------
 * Understands how to print a C-string stored
 * inside a vector.  The target FILE * should
 * be passed in via the auxData parameter.
 */

static void PrintString(void *elemAddr, void *auxData)
{
  char *word = *(char **)elemAddr;
  FILE *fp = (FILE *) auxData;
  fprintf(fp, "\t%s\n", word);
}

the thing is that this code was given tome by the project file so it cant be wrong..i suspect there is something wrong what i am calling vfree ON...?

FreeString expects a pointer to the thing being freed, not the thing itself. For this to work, v->elems needs to be a pointer to a pointer, in other words it needs to be set up like so:

Code:

v->elems = malloc(10 * sizeof(char *));
v->elems[0] = malloc(256); // a C-string of 256 chars -- this is what will get freed by FreeString
v->elems[1] = malloc(256); // and so on