free() a char* once it's been cycled through.

[xwielder]

If I _strdup() a char*, and they start cycling through it's pointers, how do I free() it at the end?

Example:

char *orig = _strdup(my.GetData("creatureLoads")); // Pulling data from a MySQL table.

while (*orig)
   {
      switch (*orig)
         {
            case '[':
               howMany = 0;
               break;
            case 'c':
               *orig++;
               creatureID = atoi(orig);
               break;
            case 'r':
               *orig++;
               roomID = atoi(orig);
               break;
            case 'x':
               *orig++;
               howMany = atoi(orig);
               break;
         }
	*orig++;
   }
   
   free(orig); // Here is where the program crashes. 

Program crashes when I try to free() orig. I'm assuming since it was _strdup()'d into memory, it needs to be free()'d. If I don't cycle thru it's pointers, it free's fine.

Thanks in advance for the advise.

[firedraco]

That's because you have incremented the pointer so you can't expect free to be able to understand what to do with this random pointer you have given it.

Just save a copy of the pointer to free later if you need it.

[xwielder]

char *orig = _strdup(my.GetData("creatureLoads")); // Pulling data from a MySQL table.
char *orig_ptr = NULL;

orig_ptr = &*orig;

while (*orig)
   {
      switch (*orig)
         {
            case '[':
               howMany = 0;
               break;
            case 'c':
               *orig++;
               creatureID = atoi(orig);
               break;
            case 'r':
               *orig++;
               roomID = atoi(orig);
               break;
            case 'x':
               *orig++;
               howMany = atoi(orig);
               break;
         }
	*orig++;
   }

orig = &*orig_ptr;
free(orig);

This above code works, is it correctly free()ing what I _strdup()'d? I think it is.

[Zhuge]

It looks correct, but you can throw away those stacked &* since that just dereferences the pointer then takes its address (effectively doing nothing). You can also just free(orig_ptr) at the end instead of assigning it to a different variable first.

[xwielder]

Yes, thank you. That's much more efficient. Tested successfully.

char *orig = _strdup(my.GetData("creatureLoads")); // Pulling data from a MySQL table.
char *orig_ptr = orig;

while (*orig)
   {
      switch (*orig)
         {
            case '[':
               howMany = 0;
               break;
            case 'c':
               *orig++;
               creatureID = atoi(orig);
               break;
            case 'r':
               *orig++;
               roomID = atoi(orig);
               break;
            case 'x':
               *orig++;
               howMany = atoi(orig);
               break;
         }
	*orig++;
   }

free(orig_ptr);
orig_ptr = NULL;
orig = NULL;