Compilare: user.c: In function ‘infix2postfix’: user.c:228:12: warning: array subscript has type ‘char’ [-Wchar-subscripts] digits[efx++] = ' '; ^ user.c:242:12: warning: array subscript has type ‘char’ [-Wchar-subscripts] digits[efx++] = ' '; ^ user.c:259:11: warning: array subscript has type ‘char’ [-Wchar-subscripts] digits[efx++] = c; ^ user.c:265:12: warning: array subscript has type ‘char’ [-Wchar-subscripts] digits[efx++] = ' '; ^ user.c:283:10: warning: array subscript has type ‘char’ [-Wchar-subscripts] digits[efx++] = ' '; ^ user.c:211:9: warning: unused variable ‘operands’ [-Wunused-variable] char *operands = "+-/*"; ^ user.c: In function ‘eval’: user.c:192:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.c: In function ‘push’: user.c:423:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.c: In function ‘peek2’: user.c:487:1: warning: control reaches end of non-void function [-Wreturn-type] } ^