Total newbie problem.. corrupted stack around variable

[Georgie Fruit]

I've spent a long, long time trying to figure out what I'm doing wrong, and I still can't find it. I'm not used to Visual Studio's Debugger, and I hope you all won't mind me asking for help. I'm getting a stack around variable error, which I know is when something tries to write out of bounds. Anyway, here's the code (my first attempt at a C++ class)

#include <iostream>
#include <string>

using namespace std;

class Studentgrade
{
private:
	char student[24];
	int quizzes[4];

public:
	void askName()
{
	cout << "Please enter the student's name: ";
		cin.getline(student, 24);
		quizzes[0] = 0;
		quizzes[1] = 0;
		quizzes[2] = 0;
		quizzes[3] = 0;
}

	void setGrade(int sc, int x)
{
	if(x>=0 && x<4)
	{
		quizzes[x] = sc;
	}
}

	void getName(char name[]) const
{
	strcpy_s(name, strlen(name), student);
}

	float getAve() const
{
	int tot = 0;
	tot = (quizzes[0] + quizzes[1] + quizzes[2] + quizzes[3]);
	return (tot/static_cast<float>(4.0));
}
};

int main()
{
	Studentgrade sg;
	char student[24];
	sg.askName();
	sg.setGrade(100,0);
	sg.setGrade(90,1);
	sg.setGrade(100,5);
	sg.setGrade(100,3);
	sg.getName(student);
	cout << student << "'s quiz average is " << sg.getAve() << endl;
	return 0;
}

If I debug with "john smith," the string never even makes it into the sg.student instance. I guess I don't understand how member functions are supposed to write to the instance rather than original class declaration (if that makes sense)

Sigh.

[Georgie Fruit]

Oh... I guess this should be in "C++ Programming" and not "Visual C++."

[Lindley]

Save yourself a great deal of time and trouble: Use std::strings rather than char arrays. You're already including the header for them anyway.

[streamer]

sg.setGrade(100,5);

you don't have fifth element in int quizzes[4];

should be:
sg.setGrade(100,2);

[Lindley]

^Not the problem.

[streamer]

^Not the problem.

Its not. Its bug.

void getName(char name[]) const

also have a problem/bug as you wish. You should pass parameter as reference.

[Lindley]

Its not. Its bug.

Maybe; or maybe it's a test to make sure that the "if" statement within the function properly catches bad input.

void getName(char name[]) const

also have a problem/bug as you wish. You should pass parameter as reference.

Reference passing is pretty much irrelevant in the case of arrays. If he were to substitute a std::string that would be true.

[GrimmRiffer]

I've spent a long, long time trying to figure out what I'm doing wrong, and I still can't find it. I'm not used to Visual Studio's Debugger, and I hope you all won't mind me asking for help. I'm getting a stack around variable error, which I know is when something tries to write out of bounds. Anyway, here's the code (my first attempt at a C++ class)

void getName(char name[]) const
{
	strcpy_s(name, strlen(name), student); //are you sure?
}

If I debug with "john smith," the string never even makes it into the sg.student instance. I guess I don't understand how member functions are supposed to write to the instance rather than original class declaration (if that makes sense)

Sigh.

Well your askName() method works fine for me, are you sure it gives you a problem? Regardless, you ought to look again at the way you're using strcpy_s, particularly the way you're telling it how long the source string is, hmm? Also, in a little project like this it's a good idea to not give a local variable the same name as a member (as you have with student in main()), the compiler will cope perfectly well but it can confuse the human.

HTH

[krmed]

I believe GrimmRiffer is on the right track.

You're strcpy_s function is incorrect...the second parameter is the size of the DESTINATION buffer - in this case it should be 24.

By using

strcpy_s(name, strlen(name), student);

you're telling it that the buffer is only the same length as the name - which doesn't leave room for the terminating NULL character.

Hope that helps.