flex: undefined reference to `yywrap' only when compiling/linking separately

Question

I've been learning to use Flex (the lexical analyser) and I've been compiling with the following command:

gcc -lfl -o test lex.yy.c

and all is well. However, I want to link it with other files, so I compile and link it separately with

gcc -c lex.yy.c

followed by

gcc -lfl -o test lex.yy.o

but gcc tells me that there is an undefined reference to yywrap(). So, what's going on here?

I'm using Flex 2.5.35, gcc 4.7.2 and ld 2.22

Answer 1

add -lfl at the end instead of beginning.

Answer 2

Use gcc lex.yy.c -ll. Otherwise it will yield an undefined reference to yywrap.

Answer 3

Alternatively, if you don't want to use the library, just #define yywrap() 1 in your .l file, or provide a yywrap() method that returns 1.

It's documented.