Question

I have a project with automake build system and there are flex/bison files there. Now I can’t understand how to include them into cmake build system. I’m trying to do this manually. Here is the project tree:

+ROOT
|---CMakeLists.txt
|---Sources/
|   |---Flex
|   |---Main
|   |---CMakeLists.txt
|---Includes/

In Flex folder there are 2 files: player_command_parser.ypp; player_command_tok.lpp. These files are from RoboCup soccer server.

I don’t really know how to use them with new build system so I decided to generate all files manually by hands:

flex --c++ player_command_tok.lpp 

This command generates lex.RCSSPCom.cc which starts with the following code:

#line 3 "lex.RCSSPCom.cc"

#define  YY_INT_ALIGNED short int

/* A lexical scanner generated by flex */

#define FLEX_SCANNER
#define YY_FLEX_MAJOR_VERSION 2
#define YY_FLEX_MINOR_VERSION 5
#define YY_FLEX_SUBMINOR_VERSION 35
#if YY_FLEX_SUBMINOR_VERSION > 0
#define FLEX_BETA
#endif

    /* The c++ scanner is a mess. The FlexLexer.h header file relies on the
     * following macro. This is required in order to pass the c++-multiple-scanners
     * test in the regression suite. We get reports that it breaks inheritance.
     * We will address this in a future release of flex, or omit the C++ scanner
     * altogether.
     */
    #define yyFlexLexer RCSSPComFlexLexer

The next step is: bison -d player_command_parser.ypp.

I got: player_command_parser.tab.cpp; player_command_parser.tab.hpp

Now I’m trying to copy all generated files to related folders: *.tab.hpp -> Includes, and added cc&cpp files into Sources/CMakeLists.txt:

set (FlexSources
    Server/Flex/lex.RCSSPCom.cc
    Server/Flex/player_command_parser.tab.cpp
)

And the compile output:

[  1%] Building CXX object Sources/Flex/lex.RCSSPCom.cc.o
In file included from /Includes/player_command_tok.h:31:0,
                 from player_command_tok.lpp:28:
/usr/include/FlexLexer.h:112:7: error: redefinition of ‘class RCSSPComFlexLexer’
/usr/include/FlexLexer.h:112:7: error: previous definition of ‘class RCSSPComFlexLexer’

What could be wrong?

Answer 1

Your compile error appears to be due to some header being included twice. You may need to make an extra file that is little more than an include guard:

player_command_tok_guarded.hpp:

#ifndef PLAYER_COMMAND_TOK_GUARDED
#define PLAYER_COMMAND_TOK_GUARDED
#include "player_command_tok.hpp"
#endif

And make your files #include this new file instead. As to integrating flex and bison into your CMake system, try something like this:

# Find flex and bison.
find_program(FLEX flex DOC "Path to the flex lexical analyser generator.")
if(NOT ${FLEX})
  message(SEND_ERROR "Flex not found.")
endif
find_program(BISON bison DOC "Path to the bison parser generator.")
if(NOT ${BISON})
  message(SEND_ERROR "Bison not found.")
endif

# Custom commands to invoke flex and bison.
add_custom_command(OUTPUT lex.RCSSPCom.cc
                   COMMAND ${FLEX} --c++ player_command_tok.lpp 
                   MAIN_DEPENDENCY player_command_tok.lpp
                   COMMENT "Generating lexer"
                   VERBATIM)
add_custom_command(OUTPUT player_command_parser.tab.cpp player_command_parser.tab.hpp
                   COMMAND ${BISON} -d player_command_parser.ypp
                   MAIN_DEPENDENCY player_command_parser.ypp
                   COMMENT "Generating parser"
                   VERBATIM)

And add the files to your file list as usual.