/usr/bin/ld: cannot find -lfl

Question

After running the following command:

g++ lex.yy.c -lfl

I get the following error:

/usr/bin/ld: cannot find -lfl

How can I solve it?

Answer 1

lex.yy.c is the default output file name for lex, the lexical analyzer preprocessor for C (and C++). The linker (ld) is looking for a file called libfl.so (if linking dynamically; it would be libfl.a if linking statically). This is the runtime library required by lexers generated by Flex, a lex implementation.

If you generated lex.yy.c yourself with flex, check that Flex is installed correctly. In addition to having the flex executable in your path, you need to have libfl.so and libfl.a (and libfl_pic.a if it exists) in your library search path (typically /usr/lib or /usr/local/lib, depending on whether Flex came from a system package or not). If you have Flex in a non-standard location, specify the library search path with -L:

~/software/flex/bin/flex mylexer.l
g++ lex.yy.c -L ~/software/flex/lib -lfl