Pop consecutive items on a stack if value is the same - c

Question

For my program I have a stack of strings and I'm trying to pop the value at the top, but if the next string on the stack has the same name I want to pop that one too and so on until all the ones on top with that name are gone. I'm probably butchering the implementation so can someone guide me in the right direction?
char *dropoff(struct stack *tosPtr)
{
printf("current tos is %s\n", tosPtr->name);
if(tosPtr == NULL)
return STACK_IS_EMPTY;
while(strcmp(tosPtr->name, tosPtr->next->name) == 0) {
stack *oldBox = tosPtr;
tosPtr = tosPtr->next;
if(oldBox == tosPtr)
tosPtr = NULL;
free(oldBox);
}
return tosPtr;
}

Answer 1

Looks like you are close. You forgot to remove the first word (you state you want to do this regardless). Then your while is nearly there. Also you are comparing two pointers that should always be un-equal (tosPtr and tosPtr->next) - unless there should be some circular reference you did not mention?
struct stack *dropoff(struct stack *tosPtr) {
printf("current tos is %s\n", tosPtr->name);
if(tosPtr == NULL)
return STACK_IS_EMPTY;
struct stack *oldBox = tosPtr;
tosPtr = tosPtr->next;
//Double check in while we didn't hit bottom of stack
while(tosPtr && strcmp(oldBox->name, tosPtr->name) == 0) {
free(oldBox); //Maybe need to free oldBox->name as well?!
oldBox = tosPtr;
tosPtr = tosPtr->next;
}
//One node left to free - maybe name?
free(oldBox);
return tosPtr ? tosPtr : STACK_IS_EMPTY; //Return empty stack if needed
}
Note you need struct in the variable definition as well if you did not typedef it, and I guess you did not because the argument is defined that way. If the name was mallocd you would need to free it is well before freeing the stack node.