Implement exit_if_null using variadic macros, fix compilation

src/util.c

@@ -21,6 +21,7 @@
 #include "data.h"
 #include "table.h"
 #include "layout.h"
+#include "util.h"
 
 int min(int a, int b) {
         return (a < b ? a : b);
@@ -30,24 +31,6 @@ int max(int a, int b) {
         return (a > b ? a : b);
 }
 
-/*
- * Checks if pointer is NULL and exits the whole program, printing a message to stdout
- * before with the given format (see printf())
- *
- */
-void exit_if_null(void *pointer, char *fmt, ...) {
-        va_list args;
-
-        if (pointer != NULL)
-                return;
-
-        va_start(args, fmt);
-        vfprintf(stderr, fmt, args);
-        va_end(args);
-
-        exit(EXIT_FAILURE);
-}
-
 /*
  * Prints the message (see printf()) to stderr, then exits the program.
  *