Exercise 6

The goal of this exercise is to familiarize yourself with the Coverity workflow.

A quick-and-dirty guide for getting started with Coverity can be found here.

Please, work in pairs!

You can submit your answers in Brightspace; the deadline for submission is Tuesday 16 April 2019, 12:00.

You can either submit your answers as a PDF file or as a report.txt. (don't forget to mention the student id of you and your partner)

Task: analyzing a small buggy program

An intrepid programmer has made some modifications to the same C program we looked at in the exercise from week 1. Analyse this program using Coverity, and examine the results in Coverity Connect.

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

int data[1024];

void pushItemOfData(int newValue)
{
    unsigned int i = 1024;
    while (i >= 0) {
        data[i] = data[i-- + 1];
    }
    data[0] = newValue;
}

int readData(int *dest, const char *fn)
{
    FILE* f = fopen(fn, "r");
    int count;
    while(!feof(f)) {
        char tmp[10];
        int value;
        fread(tmp, 10, 1, f);
        value = atoi(tmp);
        if(value <= 0) return count;
        pushItemOfData(value);
        count++;
    }
    fclose(f);
}

int main(int argc, char **argv)
{
    readData(data, "data.txt");
    return 0;
}

You can download this source code here.

Instructions

1. In Exercise 1, you have already reviewed the function pushItemOfData. Perform a similar code review for readData.

2. Analyze the program using Coverity, and compare the results it finds with your manual review.

Questions

1. Describe the issues found by Coverity, and if possible propose a fix. (Optionally, you can try to analyze your fixed version.)

2. Can you find a functional defect in the code that is not reported by Coverity?