A short implementation of a stack for strings with several benefits:

• the stack expands automatically as elements are pushed and shrinks as elements are popped.
• in case the total size of the stack is known before usage, then the stringStackCreate function will pre-allocate all the queue elements which will make ulterior operations faster since they will not suffer from the slowdowns of realloc.

stringStack.c

///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2015 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
//                                                                       //
//   stringStack                                                         //
//                                                                       //
//   An implementation of a stack of strings.                            //
//   Implemented functions:                                              //
//       - push                                                          //
//       - pop                                                           //
//       - is empty                                                      //
//       - count                                                         //
//       - size                                                          //
//       - print                                                         //
//                                                                       //
///////////////////////////////////////////////////////////////////////////
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
/* The stringStack structure with top being the index of the next element 
 * to be inserted in stack (the top-most element to be found at top - 1).
 */
typedef struct {
   int size;
   char **store;
   int top;
} stringStack;
 
// Zero or one arguments for stringStackCreate_Internal.
#define stringStackCreate_0() stringStackCreate_Internal(1)
#define stringStackCreate_1(x) stringStackCreate_Internal(x)
#define _FUNC_OVERRIDE(_1, FUNC) FUNC
#define stringStackCreate(...) _FUNC_OVERRIDE(stringStackCreate_1(__VA_ARGS__), stringStackCreate_0())
#define stringStackIsEmpty(s) (s->top == 0)
#define stringStackSize(s) s->size
#define stringStackCount(s) s->top
 
/*
 * Creates a new stringStack with a given size.
 */
stringStack* stringStackCreate_Internal(int size) {
   stringStack *s = (stringStack*)calloc(1, sizeof(stringStack));
   if ((s->store = (char**)calloc(size, sizeof(char *))) == NULL)
       return NULL;
   s->size = size;
   s->top = 0;
   return s;
}
 
/*
 * Clears a stringStack and returns a pointer to a new empty stack.
 */
stringStack* stringStackClear(stringStack *s) {
    if (s != NULL)
        free(s);
    return stringStackCreate(1);
}
 
/*
 * Pushes an element onto the stringStack.
 */
void stringStackPush(stringStack *s, char *e) {
   if (s->top > s->size - 1)
       s->store = (char**)realloc(s->store, ++s->size * sizeof(char *));
   s->store[s->top] = (char*)calloc(strlen(e) + 1, sizeof(char));
   strncpy(s->store[s->top], e, strlen(e) + 1);
   ++s->top;
}
 
/*
 * Pops an element off the stringStack or returns NULL in case the
 * stack is empty.
 */
char *stringStackPop(stringStack *s) {
   char *e;
   if (stringStackIsEmpty(s))
       return NULL;
   --s->top;
   e = (char *)calloc(strlen(s->store[s->top]) + 1, sizeof(char *));
   strncpy(e, s->store[s->top], strlen(s->store[s->top]) + 1);
   return e;
}
 
/*
 * Prints out the elements of the stringStack.
 */
void stringStackPrint(stringStack *s) {
    int i;
    if (stringStackIsEmpty(s)) {
        printf("Stack is empty.\n");
        return;
    }
    printf("Elements in the stack: ");
    i = s->top - 1;
    do {
        printf("%s ", s->store[i]);
    } while (--i > -1);
    printf("\n");
}
 
int main(void) {
    stringStack *q = stringStackCreate(2);
    printf("stack size: %d\n", stringStackSize(q));
    stringStackPush(q, "Good");
    stringStackPush(q, "Day");
    stringStackPush(q, "!");
    stringStackPrint(q);
    printf("stack size: %d\n", stringStackSize(q));
    printf("number of elements in the stack: %d\n", stringStackCount(q));
    printf("Pop: %s\n", stringStackPop(q));
    printf("Pop: %s\n", stringStackPop(q));
    stringStackPrint(q);
    printf("Pop: %s\n", stringStackPop(q));
    stringStackPrint(q);
}