can't figure out where the heap overwriting is - c++

Question

#include<iostream>
using namespace std;
class Text{
public:
~Text(){
delete data;
}
char* data{};
int mSize{};
void fill(char* stringInput) {
mSize = strlen(stringInput);
data = new char [mSize];
for (int i = 0; i < mSize; i++){
data[i] = stringInput[i];
}
}
};
class myString{
public:
explicit myString(int size){ // constructor
strAmount = size;
strings = new Text [size];
}
~myString(){ // destructor
delete[] strings;
}
void addString(char* input){
strings[filledAmount].fill(input);
filledAmount++;
}
void delString(int pos){
for ( int i = pos; i < filledAmount; i++){
swap(strings[i], strings[i+1]);
}
strings[filledAmount].data = nullptr;
strings[filledAmount].mSize = 0;
filledAmount--;
}
void eraseEverything(){
for ( int i = 0; i < filledAmount; i++){
strings[i].data = {};
strings[i].mSize = 0;
}
filledAmount = 0;
}
int maxString() const {
int index{};
for ( int i = 0 ; i < filledAmount; i++){
if (strings[i].mSize > strings[index].mSize){
index = i;
}
}
return index;
}
int charAmount(){
int counter{};
for(int i = 0 ; i < filledAmount; i++){
counter+=strings[i].mSize;
}
return counter;
}
double digitPercentage(){
int digitsAmount{};
for(int i = 0; i < filledAmount; i++){
for ( int j = 0; j < strings[i].mSize; j++){
if (isdigit(strings[i].data[j])){
digitsAmount++;
}
}
}
double digitPercent = (digitsAmount/(double)charAmount())*100;
return digitPercent;
}
int filledAmount{};
int strAmount{};
Text* strings;
};
void render_text(myString& obj) {
for (int k = 0; k < obj.filledAmount; k++) {
for (int i = 0; i < obj.strings[k].mSize; i++)
cout << obj.strings[k].data[i];
cout << endl;
}
cout << endl;
}
int main(){
myString a(5);
a.addString((char *) "zxc 1v1 forever shadow fiend");
a.addString((char *) "This is a string");
a.addString((char *) "12345");
a.addString((char *) "Hello");
a.addString((char *) "A1oha Dance");
render_text(a);
a.delString(1);
render_text(a);
int maxInd = a.maxString();
cout << "Max string :\n";
for (int i = 0; i < a.strings[maxInd].mSize; i++) {
cout << a.strings[maxInd].data[i];
}
cout << "\n\n";
}
Please help me find the crash point. I suppose it crashes in the destructor pole, but I still can't figure it out.
This is something like a self-written string class, the problem is that I can't find the place where the problems start.
I also have a thought that the destructor tries to delete too much memory from the heap so the compiler prevents it from doing that. Can I somehow change the size of the strings array?

Answer 1

I have fixed all your memory errors, with the help of address sanitizers
The main change here is:
Add copy constructors and copy assignment operators
Manually delete the last element in the function delString
Though that the code now works, it's not a true modern c++ style code. I highly recommend that your using std::string to replace your Text class. Use std::vector to replace the dynamic array. Then you will stay away from the pain of memory errors. The delString should be replaced with vector::erase,which is much neat than your hand write algorithm.
https://en.cppreference.com/w/cpp/string/basic_string
https://en.cppreference.com/w/cpp/container/vector
I strongly recommend rewriting the code with std::string and std::vector
#include <cstring>
#include <iostream>
using namespace std;
class Text {
public:
~Text() { delete[] data; }
char* data{};
int mSize{};
Text() = default;
Text(const Text& oth) {
mSize = oth.mSize;
data = new char[mSize];
std::copy(oth.data, oth.data + oth.mSize, data);
}
Text& operator=(const Text& oth) {
delete[] data;
mSize = oth.mSize;
data = new char[mSize];
std::copy(oth.data, oth.data + oth.mSize, data);
return *this;
}
void fill(char* stringInput) {
mSize = strlen(stringInput) + 1;
data = new char[mSize];
for (int i = 0; i < mSize; i++) {
data[i] = stringInput[i];
}
}
};
class myString {
public:
explicit myString(int size) { // constructor
strAmount = size;
strings = new Text[size];
}
myString(const myString& oth) {
strAmount = oth.strAmount;
strings = new Text[oth.strAmount];
for (size_t i = 0; i < strAmount; ++i) {
strings[i] = oth.strings[i];
}
}
myString& operator=(const myString& oth) {
delete[] strings;
strAmount = oth.strAmount;
strings = new Text[oth.strAmount];
for (size_t i = 0; i < strAmount; ++i) {
strings[i] = oth.strings[i];
}
return *this;
}
~myString() { // destructor
delete[] strings;
}
void addString(char* input) {
strings[filledAmount].fill(input);
filledAmount++;
}
void delString(int pos) {
for (int i = pos; i < filledAmount; i++) {
swap(strings[i], strings[i + 1]);
}
delete[] strings[filledAmount].data;
strings[filledAmount].data = nullptr;
strings[filledAmount].mSize = 0;
filledAmount--;
}
void eraseEverything() {
for (int i = 0; i < filledAmount; i++) {
strings[i].data = {};
strings[i].mSize = 0;
}
filledAmount = 0;
}
int maxString() const {
int index{};
for (int i = 0; i < filledAmount; i++) {
if (strings[i].mSize > strings[index].mSize) {
index = i;
}
}
return index;
}
int charAmount() {
int counter{};
for (int i = 0; i < filledAmount; i++) {
counter += strings[i].mSize;
}
return counter;
}
double digitPercentage() {
int digitsAmount{};
for (int i = 0; i < filledAmount; i++) {
for (int j = 0; j < strings[i].mSize; j++) {
if (isdigit(strings[i].data[j])) {
digitsAmount++;
}
}
}
double digitPercent = (digitsAmount / (double)charAmount()) * 100;
return digitPercent;
}
int filledAmount{};
int strAmount{};
Text* strings = nullptr;
};
void render_text(myString& obj) {
for (int k = 0; k < obj.filledAmount; k++) {
for (int i = 0; i < obj.strings[k].mSize; i++)
cout << obj.strings[k].data[i];
cout << endl;
}
cout << endl;
}
int main() {
myString a(6);
a.addString((char*)"zxc 1v1 forever shadow fiend");
a.addString((char*)"This is a string");
a.addString((char*)"12345");
a.addString((char*)"Hello");
a.addString((char*)"A1oha Dance");
render_text(a);
a.delString(1);
render_text(a);
int maxInd = a.maxString();
cout << "Max string :\n";
for (int i = 0; i < a.strings[maxInd].mSize; i++) {
cout << a.strings[maxInd].data[i];
}
cout << "\n\n";
return 0;
}