CODEWITHSUNDEEP
cstringgenericspointers
alex777
alex777

Reputation: 167

comparing strings with strcmp-crash

I am experimenting with pointers and strings. In the following code, everything is tested (you can compile and run yourselves), but I keep crashing when I am trying to use strcmp. The code runs without warnings in codeblocks. Can you please point out my mistake that makes the program crash?? 

    #include<stdio.h>
    #include<stdlib.h>
    #include<string.h>

    int main() 
    {
        int choice,x=7,k,q,cmp,j=0,i=0,N;
        char v[5],str[80],c[5];
        char *B[11][2]=
        {"-----","0",
         ".----","1",
         "..---","2",
         "...--","3",
         "....-","4",
         ".....","5",
         "-....","6",
         "--...","7",
         "---..","8",
         "----.","9",
         NULL,NULL};

         printf("Give a stream");
         if(gets(str)) printf("%s\n",str);
         fflush(stdin);
         i=0;
         while(str[i])
         {
             q=0;
             j=i+1;
             while(q%5!=0)
             {
                 v[j]=str[j];
                 puts(v);
                 j++;
                 q++;
             }
             printf("Hello");
             for(k=0; k<11; k++)
             {
                 strcpy(c,B[k][0]);
                 printf("%s",c);
                 x=strcmp(v,c);
                 //Problem:
                 printf("%d",c);
                 if(x==0) printf("hi");
             }
             i=i+1;
             j++;
        }
    }

Upvotes: 2

Views: 1557

Answers (3)

notbad
notbad

Reputation: 2887

This program will dump when k=10,because B[10][0] = NULL.strcpy(char *dest, const char *src) will dump when src=null.

Upvotes: 1

SomeWittyUsername
SomeWittyUsername

Reputation: 18358

You aren't filling the v with data. The condition while(q%5!=0) is false on entry since q == 0. This leaves v uninitialized, i.e. containing garbage.

Upvotes: 1

codaddict
codaddict

Reputation: 455252

You are doing:

strcpy(c,B[k][0]);

Now c is declared as:

char c[5];

and B[k][0] has 5 characters. Since you want c to be a NUL terminated char array, you must has space to accommodate the NUL char and use strncpy

Upvotes: 1

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