test return from function and printf %d conversion

test.txt

@@ -1,11 +1,14 @@
-#!./main
-
-// -*- C -*-
+#!./main 								-*- C -*-
 
 #include <stdio.h>
 
+int foo(int a)
+{
+    return 42;
+}
+
 int main(int argc, char **argv)
 {
-    printf("hello, world\n");
+    printf("hello, world %d\n", foo(argc));
     return 0;
 }