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Heap detection after normal block

I have the following code, and I'm not sure why I get a heap error message when it hits the Myclass destructor. I believe that I am freeing memory correctly?

#include <iostream>
#include <vector>
using namespace std;

class MyClass{
private:
    char* mp_str;
public:
    MyClass():mp_str(NULL){}
    ~MyClass(){
        delete [] mp_str;
    }

    void setString(const char* str);
    void printString();
};

int main(){
    MyClass* a = new MyClass();
    std::vector<MyClass> myVector;

    myVector.push_back(*a);

    a->setString("Hello World");
    myVector[0].setString("Goodbye world");

    a->printString();
    myVector[0].printString();

    return 1;
}

void MyClass::setString(const char* const str){
    if(!str)
        return;

    size_t len = strlen(str);

    if(!this->mp_str){
        this->mp_str = new char[len];
        memset(mp_str, 0, len+1);
    }
    strncpy(mp_str, str, len);
}

void MyClass::printString(){
    if(this->mp_str)
        cout << mp_str;
    else
        cout << "No string found";
}

EDIT : (Fixed code)

void MyClass::setString(const char* const str){
    if(!str)
        return;

    size_t len = strlen(str);

    if(!this->mp_str){
        this->mp_str = new char[len+1];
        memset(mp_str, 0, len+1);
    }
    strncpy(mp_str, str, len);
}

in main (), I also added

delete a;

before calling return 1;

+5
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2 answers

You need to highlight the length of the string +1 to account for the null value. You are right about him.

if(!this->mp_str){
    this->mp_str = new char[len+1];
    memset(mp_str, 0, len+1);
}
+8
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(Added after Raphael's answer, as it should be.)

, , , , , , , ( mp_str), .

TROT , - . std::string char * -, TRoT-:

class MyClass{
private:
    std::string mp_str;
public:
    void setString(const char* str) { mp_str = str ? str : ""; }
    void printString() {
        if (mp_str.size()) std::cout << mp_str;
        else std::cout << "(mp_str is empty)";
    }
};
+1

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