Segmentation fault with shared pointers

Question

What's wrong with this code (I minimized my whole code)? I can't figure out why pu.useIt(); causes a segmentation fault.

#include <memory>

using namespace std;

class Person {
    private:
    shared_ptr<string> name;

    public:
    void setName(shared_ptr<string> name) {
        this->name = name;
    }

    shared_ptr<string> getName() {
        return name;
    }
};

class PersonCreator {
    shared_ptr<Person> person;

    public:
    void createAmy() {
        shared_ptr<string> amysName = make_shared<string>("amy");
        person->setName(amysName);
    }
};

class PersonUser {
    public:
    void useIt() {
        PersonCreator pc;
        pc.createAmy();
    }
};

int main()
{
    PersonUser pu;
    pu.useIt();

    return 0;
}

rafix07 · Accepted Answer · 2019-03-24 14:46:10Z

2

You need to initialize person, now it is empty, default ctor of shared_ptr means that it points to nullptr:

void createAmy() {
        shared_ptr<string> amysName = make_shared<string>("amy");
        person = std::make_shared<Person>();  // added
        person->setName(amysName);
    }

answered Mar 24, 2019 at 14:46

rafix07

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3 Comments

user1 Over a year ago

Is default ctor of shared_ptr an extra information, you get? I only get return code 139

rafix07 Over a year ago

@Ben I don't understand, can you clarify your question? You got 139 exit code because there was not Person instance pointed by person, so setName was called for nullptr pointer. After this modification is your app still crashing?

user1 Over a year ago

Actually my minimization is wrong... Your answer is totally correct for my question.

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