Re: [Flex-help] undefined reference to 'yylex'

[Arthur S. <asc...@at...>]

What I do is to create a separate header file containing a reference to lex(). Such as:

// <lex.h>
    /**
     *@brief Scanner Name.
     */
    extern int lex( parser::semantic_type* yylval
                          , parser::location_type* yylloc);

where I am interfacing to a Bison generated C++ file and a C generated LEX file. In my Bison generated code I include a reference to this header file as in:

    %{
        # include "lex.h"
     %}

where the brackets, %{ and %}, specify where in the generated Bison file to place the include statement.

Seems to work.

art




________________________________
 From: Michele Bert <mic...@gm...>
To: fle...@li... 
Sent: Thursday, April 10, 2014 5:58 AM
Subject: Re: [Flex-help] undefined reference to 'yylex'
 

2014-04-10 11:43 GMT+02:00 liugongquan123 <liu...@16...>:
> /usr/local/lib/libfl.so:undefined reference to 'yylex'
> collect2:ld returned 1 exit status
> As I can see, yylex() is defined in /flex-2.5.39/yylex.c, and "/usr/local/lib/libfl.so " is
> installed by flex "make install", why there are such errors,and how to resolve it?

As far as I understand, yylex() is the function genereted by flex, so
it is not provided by flex libraries themselves.
If you write <yourfile>.flex, and run it through flex, it generates
<yourfile>.c, which contains the function yylex(). You have to compile
that program, and link it to the final package.

Is it right?
-- 
Michele


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