custom-reference-error.c:18: Error: Call to undeclared function 'printf'
custom-reference-error.c:19: Error: Undeclared identifier 'n'
custom-reference-error.c:21: Warning: Control reaches end of non-void function [-Wreturn-type]
custom-reference-error.c:21: Warning: Parameter 'argc' is never used
custom-reference-error.c:21: Warning: Parameter 'argv' is never used