small program stuck at segmentation fault (mean, median... using arrays)

Code:

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#include<stdio.h>#include<math.h>


double mean(int marks[], int n);
double variance(int marks[], int n);
double stdDev(int marks[], int n);
double mode(int marks[], int n);
void sort(int marks[], int n);


int main(){
   
    int n;
    int t2, t3, t4;
    double t1;
    printf("test0");




   






    FILE *inFile;


    inFile=fopen("marks.txt", "r");
    if (inFile==NULL)
    {
        printf("File open error!\n");
        return 0;
    }
    printf("test1");
   
    int marks[n];
    n=0;
    printf("test2");
    while((fscanf(inFile, "%d", &marks[n]))==1) n++;
    printf("%d\n", n);
   




    t1=mean(marks, n);
    t2=variance(marks, n);
    t3=stdDev(marks, n);
    t4=mode(marks, n);


    printf("%lf %d %lf %d, mean, variance, stdDev, mode", t1, t2, t3, t4);
    fclose(inFile);
    return 0;
}




double mean(int marks[], int n){
    int i;
    int sum=0;
    for(i=0; i<n; i++) sum+=marks[i];
    return (1.0*sum/n);
}


double variance(int marks[], int n){
    int i;
    double ave, varsum;
    varsum=0;
    ave=mean(marks, n);
    for (i=0; i<n; i++) varsum+=(marks[i]-ave)*(marks[i]-ave);
    return (varsum/n);
}
double stdDev(int marks[], int n){
    int i;
    double var;
    var=variance(marks, n);
    return (sqrt(var));
}


double mode(int marks[], int n){
    int i, count=0;
    double mid;
    mid=n/2.0;
    sort(marks, n);
    for(i=0; i<n; i++){
        count=+marks[i];
        if (count==mid) return ((marks[i]+marks[i+1])/2.0);
        if (count>mid) return(marks[i]);}
        return 0;




    }


    void sort(int marks[], int n){
        int sorter[n];
        sorter[0]=marks[0];
        int i, temp;
        for(i=1; i<n; i++){
            if (marks[i]>=sorter[i]) sorter[i+1]=marks[i];
            else {
                temp=sorter[i];
                sorter[i]=marks[i];
                sorter[i+1]=temp;
            }
        }


            for (i=0; i<n; i++) marks[i]=sorter[i];
            return;}

---

I can't find where the error occurs. The function names represent what the function does (finds mean etc.). I tried some error testing printf, but even those do not print. :(

int marks[n];
n=0;
printf("test2");
while((fscanf(inFile, "%d", &marks[n]))==1) n++;
printf("%d\n", n);

None of this makes any sense.
n is uninitialised at the time you create your array - who knows what that is going to give you.

What you DON'T have is an array that magically expands with every increment of n in that loop.

Use two while loops
- one to simply count how many integers would be read
- allocate the space
- fseek() back to the start of the file, and clearerr() to reset end of file status
- read at most n integers from the file.

Yep - exactly what Salem said. Count the numbers, then allocate the space, then read them.


Is the compiler warning you about this line?

Code:

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int marks[n];

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I'd expect most compilers to complain about this: something like "using uninitialised variable", or "variable may not be initalised". It's worth taking notice of compiler warnings!

sorry, i started on learning array yesterday. my lecture notes are vague as hell :(. working on it starting now

Thanks to you, the segmentation error is gone, but I think I do not know the right way to pass array from one function to another:
http://cboard.cprogramming.com/c-programming/142377-how-pass-array-one-function-into-another-variance-mean.html