Segmentation fault error with structures - c++

Question

I have no idea where the segmentation error is coming from ... Any ideas?
I am working with structures for an assignment
TestResult testResultFactory(std::string name, double mark)
{
//creating an object of TestResult
TestResult car;
car.name = name;
car.mark = mark;
return car;
}
Student studentFactrory(std::string name)
{
//Creating an object of student
Student house;
house.name = name;
house.testResults = 0;
house.numTestResults = 0;
return house;
}
void addTestResult(Student * student, std::string testName, double testMark)
{
//First we need to create a new array
(student->numTestResults)+=1;
TestResult *newTestArray = new TestResult[(student->numTestResults)];
//Now we loop through the old array and add it to the new one
int index = (student->numTestResults);
for (size_t i = 0; i < (index-1); i++)
{
newTestArray[i] = testResultFactory((student->testResults[i].name),(student->testResults[i].mark));
}
//Now we need to add the new student to the end of the array
newTestArray[index] = testResultFactory(testName, testMark);
(student->testResults) = newTestArray;
}
string studentBest(Student const * student)
{
//create variables as temps
string highestName;
double highestMark;
int index = (student->numTestResults);
//Setting the two variables to the first value
highestName = (student->testResults[0].name);
highestMark = (student->testResults[0].mark);
//Using a while loop to compare and get the best
for (size_t i = 0; i < index; i++)
{
if((student->testResults[i].mark)> highestMark)
{
highestMark = (student->testResults[i].mark);
highestName = (student->testResults[i].name);
}
}
//returning the string they want
string send = (highestName)+ " "+ doubleToString(highestMark)+ "%";
return send;
}
double studentAverage(Student const * student)
{
//Variables used as temps
double average = 0;
double counter = 0.0;
double running = 0;
int index = (student->numTestResults);
//Now we need to loop through each one and add to running and counter
for (size_t i = 0; i < index; i++)
{
counter++;
running += (student->testResults[i].mark);
}
//calculating the average;
average = (running)/counter;
return average;
}
void destroyStudent(Student * student)
{
delete [] (student->testResults);
(student->testResults)=0;
}
Subject subjectFactory(std::string name)
{
//Creating an object to use in subject factory
Subject lamp;
lamp.name = name;
lamp.numStudents = 0;
lamp.studentsAllocated = 0;
lamp.students = 0;
return lamp;
}
MY guess is that the error occurs because of an out of bounds array or an pointer not worked with correctly .
int getStudentIndex(Subject const * subject, std::string studentName)
{
int index;
int count = (subject->numStudents);
//loop to find the names and set index
for (size_t i = 0; i < count; i++)
{
if(studentName == ((subject->students[i].name)))
{
index = i;
}
else index = -1;
}
return index;
}
void addStudent(Subject * subject, std::string studentName)
{
//Variables as temps
Student *pointer =0;
int index = getStudentIndex(subject,studentName);
if(index != -1)
{
//Now we need to see if they are large enough
if((subject->studentsAllocated)==0)
{
//Set the allocated to 2
(subject->studentsAllocated) = 2;
pointer = new Student[2];
//Figure this out later
pointer[1] = studentFactrory(studentName);
(subject->students) = pointer;
}
else
{
//increase SA with 1.5
(subject->studentsAllocated) = (subject->studentsAllocated) * 1.5;
pointer = new Student[(subject->studentsAllocated)+1];
int count = (subject->studentsAllocated);
//Now we need to put all the other students in
for (size_t i = 0; i < count-1; i++)
{
pointer[i] = (subject->students[i]);
}
pointer[(subject->studentsAllocated)+1] = studentFactrory(studentName);
(subject->studentsAllocated) += 1 ;
}
//Once done just seet one equal to
(subject->students) = pointer;
}
else return;
}
void removeStudent(Subject * subject, std::string studentName)
{
//First get temps
int index = getStudentIndex(subject ,studentName);
int number = (subject->studentsAllocated);
int i = index;
//delete student
if(index == -1) return;
destroyStudent(&(subject->students)[index]);
//loop to shift the things
while (i<(number -1))
{
(subject->students)[i] = (subject-> students[i+1]);
}
//Removing the last one
(subject->numStudents) -= 1;
}
bool addTestResult(Subject * subject, std::string studentName, std::string testName, double testMark)
{
int index = getStudentIndex(subject ,studentName);
if(index != -1)
{
addTestResult(&(subject->students [index]),testName,testMark);
return true;
}
else
return false;
}
void printSubjectSummary(Subject const * subject)
{
cout<<(subject->name)<< ": with "<<(subject->numStudents)<<" students"<<endl;
//Variables to use in the loop
size_t indexLoop = subject->numStudents;
int i=0;
while (i< indexLoop)
{
cout<<(subject->students[i].name)<<" Average: "<<studentAverage(&(subject->students[i]))<<", Best: "<<studentBest(&(subject->students[i]))<<endl;
}
}
void destroySubject(Subject * subject)
{
//Variables
size_t indexLoop = subject->numStudents;
for (size_t i = 0; i < indexLoop; i++)
{
destroyStudent(&(subject->students[i]));
}
delete [] subject->students;
subject->students =0;
}
I can not seem to find where the segmentation error is coming from. Even restarted the whole assignment from scratch and still seem to get errors.
Can someone please help or indicate where the fault could be coming from.
Over here we have the structs.h file that is included in my code above
#ifndef STRUCTS_H
#define STRUCTS_H
struct TestResult{
double mark;//the test mark as a percentage
std::string name;//the test name
};
struct Student{
std::string name;
TestResult * testResults;//an arry of TestResults
size_t numTestResults;//the number of results for this student (also the size of the array)
};
struct Subject{
std::string name;
Student * students;//an array of Students
size_t numStudents;//the number of students added to the subject
size_t studentsAllocated;//the size of the Student arry(must never be smaller that numStudents)
};
#endif

Answer 1

There are so many logical errors in there that the root cause (or causes; there are quite a few candidates) could be pretty much anywhere.
getStudentIndex returns -1 unless the student is the last one in the array, and an indeterminate value for the first one you add, so adding the first student to a subject is undefined.
addStudent only adds a student if they're already taking the subject.
It also (for some inexplicable reason) allocates an array of two Students, leaving the first element uninitialised.
Using this first element is, of course, undefined.
In the other branch, it first claims that the number of allocated students is * 1.5, but then only allocates + 1.
This will undoubtedly lead to problems.
There is a recursion in addTestResult that will never terminate.
There are most likely other problems as well – this was just a quick glance.
Start with fixing these.
And do learn about constructors and destructors so you can get rid of those "factory" and "destroy" functions.