Thread: a = new char[6] and yet a is much longer than 6?!?

Hi people, Im making a text editor and I have a big problem, here is the code where I have the problem

Code:

mytext = new char[count+lenght];

I have debugged my program many times and Im sure that count == 0 and lenght == 6, yet mytext always ends up bigger and when I print it on the screen it ends up printing a lot of giberish thats shouldnt be there!

Here is the .cpp file

Code:

#include "main.h"

int main() {
	Text paper;
	char test[] = "Marcos";

	paper.addtext(test, strlen(test));
	paper.showtext();
	return 0;
}

// Class Text
Text::Text() {
	mytext = new char[1];
	mytext = NULL;
	count = 0;
}

Text::~Text() {
	delete[] mytext;
}

void Text::addtext(char *a, int lenght) {
	char *temp; // temporarily hold what was already on mytext

	if (mytext != NULL) {
		temp = new char[count];
	
		strcpy(temp, mytext);
	
		delete[] temp;
	} else {
		temp = "";
	}

	delete[] mytext;

	mytext = new char[count+lenght]; // make it long enough to hold what it had before + what we will add new
	for (int i = 0; i < count; i++)
		mytext[i] = temp[i]; // add what we had before

	for (int i = 0; i < lenght; i++)
		mytext[count+i] = a[i]; // add the new text after what we had before
}

void Text::deletetext() {
}

void Text::showtext() {
	printf("%s", mytext);
}

Here is the .h file

Code:

#include <stdlib.h>
#include <fstream>

class Text {
public:
	Text();
	~Text();

	void addtext(char *, int);
	void deletetext();
	void showtext();
private:
	char *mytext;
	int count;
};

Sorry for the trouble guys, but I really cant solve this.

Thanks.

Then, you "delete[] mytext", which will break because at this point "mytext" is NULL.

Deleting a NULL pointer is a perfectly legal no-op.

Thanks for the interest people, I have done some work on it and now it works (bearly )
This is what I have now in the .cpp file:

Code:

#include "main.h"

int main() {
	Text paper;
	char buff[100];

	while (1) {
		scanf("%s", buff);
		rewind(stdin);
		if (!strcmp(buff, "-exit"))
			break;
		paper.addtext(buff, strlen(buff));
	}

	paper.savetofile();
	return 0;
}

// Class Text
Text::Text() {
	mytext = new char;
	mytext = NULL;
	count = 0;
}

Text::~Text() {
	delete[] mytext;
}

void Text::addtext(char *a, int lenght) {
	char *temp;

	if (mytext != NULL) {
		temp = new char[count];

		for (int i = 0; i < count; i++)
			temp[i] = mytext[i];

		temp[count] = NULL;
	} else {
		temp = "";
	}

	delete[] mytext;

	mytext = new char[(count+lenght)+1];

	for (int i = 0; i < count; i++)
		mytext[i] = temp[i];

	for (int i = 0; i < lenght; i++)
		mytext[count+i] = a[i];

	mytext[count+lenght] = NULL;

	count += lenght;
}

void Text::deletetext() {
}

void Text::showtext() {
	printf("%s", mytext);
}

void Text::savetofile() {
	std::ofstream fout;

	fout.open("Text.txt");
	fout << mytext << "\n";
	fout.close();
}

Im not really sure if this fixed the memory leak, (I dont quite understand them yet).
Also, I was wondering what function I could use in main() to get a whole sentence because scanf() apearently stops reading after a space.

Originally Posted by Marcos

Code:

...

// Class Text
Text::Text() {
    mytext = new char;  // Get rid of this line to fix memory leak
    mytext = NULL;
    count = 0;
}

...

Im not really sure if this fixed the memory leak, (I dont quite understand them yet).

No, you haven't solved the memory leak, see above in red.

Ok, so I finally got rid of the memory leak.
But I dont understand what I should put in the first parameter of getline() (_Istr).
Can someone use it in an example?

Originally Posted by Marcos

Ok, so I finally got rid of the memory leak.
But I dont understand what I should put in the first parameter of getline() (_Istr).
Can someone use it in an example?

For your purposes, I think you would want:

Code:

cin.getline(buff,sizeof(buff),'\n');

Yeah that worked great, thanks

>I guess I'm still oldschool
Of what old school do you speak? Freeing a null pointer has always been a no-op, IIRC.