Yacc/Lex giving segmentation fault with this code

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I am trying out a homework assignment. The assignment is to generate Intermediate Code. For this I am running the following Yacc program, along with Lex. However, it is giving me a segmentation fault. Why does it give a segmentation fault? Here is the code.

%{
#include<stdio.h>
#include<malloc.h>
#include<string.h>
#include<ctype.h>

char datatype[5];
char temporaryVariable[5];
int assignment=0;
int tempvarnum=0;

struct sym
{
    char datatype[5];
    char varname[5];
    int size,location;
    struct sym *next;
}*first;

struct quadruple
{
    char *src1;
    char *src2;
    char *op;
    char *tmp;
    struct quadruple *next;
}*qfirst;

char* typeOf(char *lab);


void yyerror(const char *st)
{}
%}

%left '+' '-'
%left '*' '/'
%right '^'
%union 
{
    struct ICG
    {
        char *lab; 
        char code[100]; 
        char datatype[5];
    }Icg;
}
%token <Icg> ID
%token INT FLOAT CHAR
%type <Icg> E

%%
S: S Decl
 | Decl 
 | S Assn
 | Assn
 ;

Decl:Type List ';' {printf("Read declaration list");}
    ;

List:List ',' ID {printf("created node\n");createNode($3.lab,datatype);}
    | ID {printf("created node\n");createNode($1.lab,datatype);}
    ;

Type: INT {strcpy(datatype,"int");}
    | FLOAT {strcpy(datatype,"float");}
    | CHAR {strcpy(datatype,"char");}
    ;

Assn:ID '=' E ';' {printf("Assignment statement");assignment=0;}
    ;


E: E '+' E {printf("Entering code");code(&$$,&$1,&$3,'+');}
 | E '-' E {code(&$$,&$1,&$3,'-');}
 | E '*' E {code(&$$,&$1,&$3,'*');}
 | E '/' E {code(&$$,&$1,&$3,'/');}
 | ID {printf("ID");strcpy($$.code,$1.lab); strcpy($$.lab,$1.lab);strcpy($$.datatype,typeOf($1.lab));}
 ;
%%

void code(struct ICG* one, struct ICG* two, struct ICG* three, char *operator)
{
    printf("In code");
    char tempvarname[5];
    char code[100];
    sprintf(tempvarname,"t%d=",tempvarnum++);
    strcpy(one->lab,tempvarname);
    strcpy(one->lab,two->lab);
    createNode(one->lab,one->datatype);
    strcpy(code,tempvarname);
    strcat(code,two->lab);
    strcat(code,three->lab);
    strcat(code,operator);
    strcat(code,"\n");

    if(assignment==0)
    {
        strcpy(one->code,code);
        assignment=1;
    }
    else
    {
        strcat(one->code,code);
    }
    createQuadruples(two->lab,three->lab,operator,one->lab);
}

void createQuadruples(char *lab2,char*lab3,char *operator,char*lab1)
{
    struct quadruple* next=qfirst;
    if(!next)
    {
        struct quadruple* new=(struct quadruple*)malloc(sizeof(struct quadruple));
        strcpy(new->src1,lab2);
        strcpy(new->src2,lab3);
        strcpy(new->op,operator);
        strcpy(new->tmp,lab1);
        new->next=NULL;
        qfirst=new;
    }
    else
    {
        while(next->next)
        {
            next=next->next;
        }
        struct quadruple* new=(struct quadruple*)malloc(sizeof(struct quadruple));
        strcpy(new->src1,lab2);
        strcpy(new->src2,lab3);
        strcpy(new->op,operator);
        strcpy(new->tmp,lab1);
        new->next=NULL;
        next->next=new;
    }
}

void displayCode()
{
    struct quadruple* temp=qfirst;
    int i=0;
    printf("\t| %s | Label | size | location |\n","Index");
    while(temp)
    {
        printf("\t|%7d|%7s|%6s|%7s|%8s|\n",i++,temp->src1,temp->op,temp->src2,temp->tmp);
        temp=temp->next;
    }   
}

char* typeOf(char *lab)
{
    struct sym *new=first;
    while(new)
    {
        if(strcmp(new->varname,lab)==0)
        {
            return new->datatype;
        }
        new=new->next;
    }
}




void createNode(char *name, char *type)
{
    struct sym* new=first;
    int size=0;
    if(strcmp(type,"char")==0)
        size=1;
    if(strcmp(type,"float")==0)
        size=4;
    if(strcmp(type,"int")==0)
        size=2;

    if(!new)
    {
        struct sym* next=(struct sym*)malloc(sizeof(struct sym));
        strcpy(next->datatype,type);
        strcpy(next->varname,name);
        next->size=size;
        next->location=0;
        next->next=NULL;
        first=next;
    }
    else
    {
        while(new->next)
        {
            new=new->next;
        }
        struct sym* next=(struct sym*)malloc(sizeof(struct sym));
        strcpy(next->datatype,type);
        strcpy(next->varname,name);
        next->size=size;
        next->location=new->location+new->size;
        next->next=NULL;
        new->next=next;
    }
}
int main()
{
    yyparse();
    printf("In main");
    displayCode();
}

And the corresponding lex file is this:

%{
#include<stdio.h>
#include "y.tab.h"
%}

letter [a-zA-Z]
digit [0-9]

%%
"int" {return INT;}
"float" {return FLOAT;}
"char" {return CHAR;}
"+"|"-"|"*"|"/"|"="|","|";" {return yytext[0];}
{letter}({letter}|{digit})* {yylval.Icg.lab=yytext;return ID;}
%%

I did try to debug the program, but it is simply getting me nowhere. And I don't even how to start debugging it. I did try with printf statements, but I found that they didn't help much.

The only thing I know for sure is that it is detecting the Identifiers.

asked 1 min ago

Rohit Shinde

181

Yacc/Lex giving segmentation fault with this code