fix pop from FIFOBuff and fix warnings for CLI

FIFOBuff/FIFOBuffChar.c

@@ -1,9 +1,8 @@
+#include "FIFOBuffChar.h"
+
 #include <stdlib.h>
 #include <stddef.h>
 #include <stdio.h>
-#include "FIFOBuffChar.h"
-
-
 
 bool FIFOBuffChar_put(FIFOBuffChar_t *fifo, char i) // Change the function parameters to match the declaration
 {
@@ -126,25 +125,39 @@ bool FIFOBuffChar_pop(FIFOBuffChar_t *fifo)
 {
     bool ok = true;
 
-    if (fifo->FirstEl_p == NULL)
-    { // buffer is empty
-        ok = false;
-    }
-    else
-    { // there is data in the buffer
-        // find the second last element
-        FIFOBuffChar_element_t* secondLastEl; = fifo->FirstEl_p;
-        while (secondLastEl->nextElement != fifo->LastEl_p)
-        {
-            secondLastEl = secondLastEl->nextElement;
-        }
+    switch (fifo->size){
+        case 0: // buffer is empty
+            ok = false;
+            break;
 
-        // remove last element
-        free(fifo->LastEl_p);
+        case 1: // singel item in buffer
+            // make buffer empty
+            free(fifo->FirstEl_p);
+            fifo->FirstEl_p = NULL;
+            fifo->LastEl_p = NULL;
+            fifo->size = 0;
+            ok = true;
+            break;
 
-        // update chain
-        secondLastEl->nextElement == NULL;
-        fifo->LastEl_p = secondLastEl;
+        default: // buffer is at least 2 element big
+            // find the second last element
+            FIFOBuffChar_element_t* secondLastEl = fifo->FirstEl_p;
+            while (
+                   secondLastEl->nextElement != fifo->LastEl_p
+                && ((FIFOBuffChar_element_t*)secondLastEl->nextElement)->nextElement != NULL
+            ){
+                secondLastEl = secondLastEl->nextElement;
+            }
+
+            // remove last element
+            free(fifo->LastEl_p);
+
+            // update chain
+            secondLastEl->nextElement = NULL;
+            fifo->LastEl_p = secondLastEl;
+            fifo->size--;
+            ok = true;
+            break;
     }
 
     return ok;