Why is my recursive program giving me a segmentation fault?

Question

I keep on getting a segmentation fault when I run my program. Segmentation faults are generally supposed to happen when the program tries to access memory which the computer can't physically address. I can't pinpoint where the problem lies.

Edits: I changed added the & when scanning the variables but that does not fix the problem of the segmentation fault

Here is my code:

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


    void userEnter(int*pattern, int n);
    void print( int * s, int n);
    void recurs( int * s, int * a, int n, int wpegs, int bpegs);
    bool Done (int*s);
    bool bPegs(int*a ,int*s, int bpegs, int wpegs, int n);
    bool wPegs(int* modcom, int* modoriginal, int*s, int wpegs, int w);
    void change(int*modoriginal, int*modcom, int i, int k, int w);

    int main(void)
    {
        int i, n, bpegs, wpegs;

        printf("Enter the pattern length: ");
        scanf("%d",&n);
        int *a = (int*)malloc((n)*(sizeof(int)));
        printf("Input the guess pattern: ");
        int pattern[n];
        userEnter(pattern, n);  
        printf("Enter the number of black pegs in the feedback: ");
        scanf("%d",&bpegs);
        printf("Enter the number of white pegs in the feedback: ");
        scanf("%d",&wpegs);
        printf("The possible key patterns are: ");
        for(i=0; i<=n-1; i++)
        {
            a[i]=0;
        }
        print(a, n);
        recurs(a, pattern, n, wpegs, bpegs);

    }

    void userEnter(int*pattern, int n)
    {
        char input[n];
        scanf("%s",&input);

        int i;
        for(i = 0; i < n-1; i++)
        {
            pattern[i] = input[i]-65;
        }
    }

    void print( int * s, int n)
    {
        int i; 
        printf( "\n" );
        for( i = n-1; i >= 0; i-- )
        {
            printf( "%c", ( s[ i ] + 65 ) );
        }
    }

    void recurs( int * s, int * a, int n, int wpegs, int bpegs)
    {

        int i;

        if(Done(s))
        {
            print( s, n);
            printf( "\nAccomplisshed!\n" );
        }

        else{
            s[ 0 ] += 1;
            for( i = 0; i < n-1; i++ )
            {
                if( s[ i ] == 6 ){
                    s[ i ] = 0;
                    s[ i + 1 ] += 1;
                }
            }
            if(bPegs(a ,s, bpegs, wpegs, n))
            {
            print( s, n);
            }
            recurs(s, a, n, wpegs, bpegs);
        }
    }

    bool Done (int*s)
        {
            int i;
            bool done=true;
            for (i=0;i<=11;i++)
            {
                if(s[i]!=5)
                {
                    done=false;
                }
            }
            return done;
        }


    bool bPegs(int*a ,int*s, int bpegs, int wpegs, int n)
    {
        int i,j,c=0;
        bool d = false;
        for(i=0; i<n-1; i++)
        {
            if(a[i]==s[i])
            {
                c++;
            }
        }
        int x =n-c;
        int* modcom; 
        int*modoriginal;
        modcom=(int*)malloc((x)*(sizeof(int)));
        modoriginal=(int*)malloc((x)*(sizeof(int)));
        int w=0;
        for(j=0; j<n-1; j++)
        {
            if(a[j]!=s[j])
            {
                modcom[w]=s[j];
                modoriginal[w]=a[j];
                w++;
            }       
        }
        if(c==bpegs)
        {
            d = wPegs(modcom, modoriginal, s, wpegs, w);
        }

        return d;

    }

    bool wPegs(int*modcom, int*modoriginal, int*s, int wpegs, int w)
    {
        int i, k, count=0;
        for(i=0; i<=w; i++)
        {
            for(k=0; k<=w; k++)
            {
                if (modoriginal[i]==modcom[k])
                {
                    count++;
                    change(modoriginal, modcom, i, k, w);
                }
            }
        }
        if(wpegs==count)
        {
            return true;
        }
        else
        {
            return false;
        }

    }

    void change(int*modoriginal, int*modcom, int i, int k, int w)
    {
        int c, o;
        for(c=i-1; c<w-1; c++)
        {
            modoriginal[c]=modoriginal[c+1];
        }
        for(o=k-1;o<w-1;o++)
        {
            modcom[o]=modcom[o+1];
        }
    }

Answer 1

Because you are not passing arguments to scanf properly, as reported by the compiler:

13421173.c:25: warning: format ‘%d’ expects type ‘int *’, but argument 2 has type ‘int’
13421173.c:25: warning: format ‘%d’ expects type ‘int *’, but argument 2 has type ‘int’
13421173.c:27: warning: format ‘%d’ expects type ‘int *’, but argument 2 has type ‘int’
13421173.c:27: warning: format ‘%d’ expects type ‘int *’, but argument 2 has type ‘int’

Correct usage looks like:

scanf("%d", &bpegs);

Answer 2

I haven't checked all the code but you should change

scanf("%d",bpegs);
printf("Enter the number of white pegs in the feedback: ");
scanf("%d",wpegs);

to

scanf("%d",&bpegs);
printf("Enter the number of white pegs in the feedback: ");
scanf("%d",&wpegs);

ie pass pointers to the ints you want scanf to write to

Answer 3

The arguments for scanf are a format and a pointer to a variable of the same type of format. In the case of integers %d requiers &d where d is of type int . For a string, like input in your function userEnter() , %s rquires a type char* , input is an array, that means input without de braces is already a pointer so you only write

scanf("%s",input);

Also you should check the limits in your for cicles. For instance in bPegs() you are allocating memory for modcom and modoriginal of size x = n - c , and in the next for cicle your limit goes to n-1, this creates a segmentation fault unless c = 1.

Answer 4

Something like:

scanf("%d",bpegs);

Makes an implicit cast from int to int pointer, so that the read integer will be written in a some random address.This random address depends on the value of bpegs, which wasn't initialized.If you used scanf plenty times, then you have to correct all these errors, and pass the address of the value to change, not the value.