MulVAL 中的错误：`mylval' 的多重定义； collect2: 错误: ld 返回 1 个退出状态

Question

I'm getting this error while compiling MulVAL with "make" command on fedora OS.

This is the error:

multiple definition of `mylval'; lex.yy.o:/home/user/Desktop/mulval/src/attack_graph/graphit.l:5: first defined here
collect2: error: ld returned 1 exit status
make: *** [Makefile:4: attack_graph] Error 1

This is the Makefile I'm compiling:

default: install

attack_graph: attack_graph.cpp attack_graph.h Queue.h lex.yy.o y.tab.cpp
g++ -g -DLINUX -Wno-deprecated lex.yy.o y.tab.cpp attack_graph.cpp -o 
attack_graph

lex.yy.c: graphit.l
    lex  -olex.yy.c graphit.l  

lex.yy.o: lex.yy.c y.tab.cpp.h
    gcc -g -c lex.yy.c -o lex.yy.o

y.tab.cpp y.tab.cpp.h: graphit.y attack_graph.h  
    bison -dv graphit.y
    mv graphit.tab.c y.tab.cpp
    mv graphit.tab.h y.tab.cpp.h

...

First few lines of graphit.y (showing where mylval is used):

#define YYSTYPE char *
    extern YYSTYPE yylval;
    extern "C"
    {
        int yyparse(void);
        int yylex(void);
        YYSTYPE* mylval = &yylval;
       int yywrap()
       {
           return 1;
       }
    }

Few lines of graphit.l (also showing where mylval is used):

%{
#include <stdio.h>
#include "y.tab.cpp.h"
#define YYSTYPE char *
YYSTYPE* mylval;
FILE **my_ptr = &yyin;
%}

%%
...
[0-9]*\.[0-9]+                *mylval=(char *)strdup(yytext); return FLOAT;
[\.\[\]\,\(\)]                 return (int) yytext[0];
[\/a-zA-Z0-9_\-\+\.\=\\]+     *mylval=(char *)strdup(yytext); return ATOM;
...
%%

The full code can be found at https://github.com/fiware-cybercaptor/mulval

I tried to modify the graphit.y file by removing the YYSTYPE* before the mylval like this:

 mylval = &yylval;

but it gave this error:

mylval does not name a type

which means that it's not defined before.

Please can anyone help?

Answer 1

I gather that you didn't write the program you're trying to compile, and I see that you filed some sort of bug report.

It's also evident that whoever did write the program had very little or no experience with flex or bison, and not much with C either. There are a great number of problems beyond the one which creates the compiler error you observed.

To fix the immediate error in graphit.l , change line 5 to:

extern YYSTYPE* mylval;

I don't believe that the variable is necessary at all; it looks to me like a clumsy solution to some Windows DLL problem. But removing the variable is more work than just making sure it has a single definition.