k&r chapter-1 question, creating a syntax checker

[karan173]

hey it is required to create a syntax checker which reports about common errors like unbalanced paranthesis etc. i hav created d following code, which complies finely and produces correct output for generally, but when i enter d source code as input, it produces wrong input, so csn u help me find d bugs:-

#include<stdio.h>
#define IN 1
#define OUT 0
int main()
{
    int c=0,prevc=0,prevprevc=0,sstate=OUT,dstate=OUT,cstate=OUT,count[256],boo=OUT,i=0,asciieq=0,line=0;
    char escape[]={'a','b','\\','0','t','n','\"','\''};
    for(i=0;i<=255;i++)
    {
        count[i]=0;
    }
 
    while((c=getchar())!=EOF)
    {
       if(c=='\n')
       line++;
       asciieq=c;                                                               /*ASCII EQ. OF C*/
       if(c=='\"' && prevc!='\\' && cstate==OUT && sstate==OUT)                                /*DOUBLE QUOTE TOGGLE*/
       dstate=!dstate;
 
       if(c=='\'' && prevc!='\\' && cstate==OUT && dstate==OUT)                                /*SINGLE QUOTE TOGGLE*/
       sstate=!sstate;
 
       if(sstate==OUT && dstate==OUT)                                           /*comment toggle*/
       { 
            if(cstate==OUT && c=='*' && prevc=='/')
            cstate=IN;
            if(cstate==IN && c=='/' && prevc=='*')
            cstate=OUT;
       }
       if(cstate==OUT)                                                          /*escape sequences*/
       {
           if(prevc=='\\' && prevprevc!='\\')
           {
               for(i=0;i<sizeof(escape);i++)
               {
                    if(c==escape[i])
                    {
                        boo=IN;
                        break;
                    }
                }
                if(boo!=IN)
                {
                    printf("Incorrect escape sequence entered\n");              /*Error 1*/
                }
            }
        }
 
       if(cstate==OUT && dstate==OUT && sstate==OUT)
       {count[asciieq]++; }
 
        prevprevc=prevc;
        prevc=c;
    }  
 
    int a='[', b=']', cx='{', d='}', e='(', f=')', g='/' ;            /*error generation*/
    boo=0;
    if(count[a]!=count[b])
    {printf("unbalanced brackets\n");boo=1;}
 
    if(count[cx]!=count[d])
    {printf("unbalanced braces\n");boo=1;}
 
    if(count[e]!=count[f])
    {printf("unbalanced paranthesis\n"); boo=1;}
 
    if(count[g]%2!=0)
   { printf("Uneven / \n");boo=1;}
 
    if(sstate==IN)
    {printf("Single character string i.e ' , not closed \n");boo=1;}
 
    if(dstate==IN)
    {printf("Character string i.e \" , not closed \n");boo=1;}
 
    if(cstate==IN)
    {printf("Comments not closed \n");boo=1;}
 
    if(boo==0)
    {printf("no errors encountered\n");}
 
    system("pause");
    return 0;
}
 

I suspect probably something is not right with the toggle for '," or comments that i have created!

[Stewart Ross]

Please tell us what you have done so far to debug your code, and in particular which lines we should be looking at.

-Stewart

[karan173]

hmm, thanks for ur response, solved myself after some effort, as i said the toggling code was not correct