Library not found for -lfl

Question

I was using flex and bison to build a simple calculator project I cloned from Github.

But after I typed make in terminal, I go

Answer 1

warning: type specifier missing, defaults to 'int'

mean that you should declare return type for main function. Place int in function difinition.

ld: library not found for -lfl

flag -l mean that compiller must use libfl.a to build programm. As @waTeim said above, for Mac OS you can use libl.a instead, but this lib can be not exist alse. There is another way is to place

%option noyywrap

at the top of flex *.l file. In this case you can compile without additional libs.