Problems With Variables C++

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hey,

I am having problem with variables, while debugging variable is automatically assigned to some random large value again and again after each line, Help me out of this plz

#include<iostream>
#include<fstream>
#include<string>
using namespace std;

char* Line_Address(string path,int Delimer,int line)
{
	char* keys;
	char* temp;
	temp=new char[70];
	temp[69]='\0';
	bool Loopbrk=false;
	int iCounter=0,iDelimer=0,i=0,count=0;
	ifstream myfile(path);
	char keystroke;
	while(myfile.good())
	{
		myfile.get(keystroke);
		if(keystroke=='!')
			iCounter++;
		while(iCounter==line)
		{
			myfile.get(keystroke);
			
			if(keystroke=='$')
				iDelimer++;
			while(iDelimer==Delimer)
			{
				myfile.get(keystroke);
				
				temp[i]=keystroke;
				i++;
				if(keystroke=='$')
				{
					Loopbrk=true;
					break;
				}
			}
			if(Loopbrk==true)
				break;
		}
		if(Loopbrk==true)
				break;
	}
	int size=strlen(temp);
	for(int i=0;i<size;i++)
		if((temp[i]>=48&&temp[i]<=57)||(temp[i]>=97&&temp[i]<=122)||(temp[i]>=65&&temp[i]<=90)||temp[i]==32)
			count++;	
	keys=new char[count+1];
	for(int i=0;i<count;i++)
		keys[i]=temp[i];
	keys[count]='\0';
	delete []temp;
	return keys;
}
int T_Delimer(string path)
{
	int iDelimer=0;
	char keystroke=' ';
	ifstream myfile(path);
	while(myfile.good())
	{
		while(keystroke!='!')
		{
			myfile.get(keystroke);
			if(keystroke=='$')
				iDelimer++;
		}
		break;
	}
	return iDelimer;
}
void main()
{
	string keystroke[10];
	int jpg=0,gif=1,Delimers=T_Delimer("student.txt");;
	char key;
	for(int i=0;i<Delimers;i++)
	{
		keystroke[i]=Line_Address("student.txt",i,gif);
	}
	fstream myfile("student.txt");
	while(myfile.good())
	{
		myfile.get(key);
		if(key=='!')
			jpg++;
		if(jpg==gif)
		{
			fstream("student.txt",ios::in);
			myfile<<" ";
		}
	}
	myfile.close();
}

////////////////student.txt//////////////

l114443$Talha Jamil$samsung$12$17$2004$UnderGraduate$!
l114445$Kamran Javed$jannat123$12$12$2009$UnderGraduate$!
l114093$Imran Khan$pluto123$11$4$2009$UnderGraduate$!
l114444$Jamil Ahmed$origin123$11$12$2009$UnderGraduate$!
l114606$Zain Malik$samsung$9$16$2009$Graduate$!
l114441$Saad Kamran$samsung$11$4$2004$Graduate$!

Posted 13-Dec-12 3:05am

saad_lah

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[no name] 13-Dec-12 9:11am

you are required to initialize each variable before using it for any purpose. declaring it only means a particular memory bunch is allotted and the value there will not be altered until requested.

any question regarding this is welcome :)

saad_lah 13-Dec-12 9:19am

could you plz show it in code

nv3 13-Dec-12 9:57am

Haven't you asked that question yesterday with regard to some parameter of your function? It seems you are having problems with the debugger. Which platform are you on and which compiler and debugger do you use?

saad_lah 13-Dec-12 10:16am

I am using visual studio 2010, though the problem was with debugger, now i managed to solve it

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Jochen Arndt · Answer 1 · 2012-12-13T04:00:00

The effects you are seeing are typical for buffer overflows.

You have two arrays with fixed sizes that are accessed without bound checking:

temp used in Line_Address() is accessed by the variable i. If i is greater or equal to 70, you will have a buffer overflow.
keystroke[10] in main() is accessed up to the index Delimers - 1. There will be a buffer overflow if Delimers is greater than 10.

To fix these, you must add code that checks the indexes and terminates the loops if the limits are reached.

You are calling strlen(temp) without terminating temp. You initially terminated it, but this will be overwritten when i becomes 69. Even when i is less than 69, you are processing garbage because strlen() may return any value between the number of assigned chars and 69. To fix this, add this line after the while loop:

C++

temp[i] = 0;

You are also copying count items from temp to keys. This will not generate a buffer overflow because you are only redaing from temp, but you may have garbage in keys when i < count.

There might be more errors that I have missed.

Pascal-78 · Answer 2 · 2012-12-13T03:40:00

Solution 1

You should initialize the full content of temp to zero and not only the last character:

C++

memset(temp,0,sizeof(temp));

or the strlen(temp) will be wrong.

Posted 13-Dec-12 3:40am

Pascal-78

Comments

saad_lah 13-Dec-12 10:16am

temp working fine

saad_lah · Answer 3 · 2012-12-13T04:09:00

Solution 3

Problem is solved by making a new project and compiling this code in it.

Posted 13-Dec-12 4:09am

saad_lah

Comments

Pascal-78 13-Dec-12 11:04am

Now with your compiled program:
did you try to look at the "temp" variable content before the strlen(temp) call?
Did you try to call the Line_Address function with these parameters: ("student.txt", 0, 0) And did you get the expected string?
And in the keystroke[0] in main(), did you see the expected value?

saad_lah 13-Dec-12 12:59pm

Sorry for the late reply,
Line_Address("student.txt",0,0) the func. fails, in order to make the func. efficient i used a check of Line and Delimer to be '1' otherwise func. gives error. and in student.txt first line is '\n' and the student data starts from 2nd line with '$' as first character....actual student.txt is given below

/////////////student.txt////////////

$l114443$Talha Jamil$samsung$12$17$2004$UnderGraduate$!
$l114445$Kamran Javed$jannat123$12$12$2009$UnderGraduate$!
$l114093$Imran Khan$pluto123$11$4$2009$UnderGraduate$!
$l114444$Jamil Ahmed$origin123$11$12$2009$UnderGraduate$!
$l114606$Zain Malik$samsung$9$16$2009$Graduate$!
$l114441$Saad Kamran$samsung$11$4$2004$Graduate$!

Problems With Variables C++

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