Can't properly insert a pair generated in code into a std::map

Question

I have a weird problem. I have a map in C++ defined like this as private in a class.

std::map<const char *, GameObject *> GameObjects;

I have a function that adds pairs to the map.

void myClass::Add(const char *name, GameObject *object)
{
    GameObjects.insert(std::make_pair(name, object));
}

It works fine if I add pairs like this.

m_myClass.Add("Example", new GameObject());

Now, the problem is in the Instantiate function, declared like this.

void myClass::Instantiate(GameObject *object)
{
    char *name = (char *)malloc(strlen("New Object ") + 12);                                  // New Object xxxxxxxxxxxx    x -> digit
    memset(name, 0, strlen("New Object ") + 12);                                              // clear
    strcpy(name, "New Object ");                                                              // copy the first part
    strcpy(name + strlen("New Object "), std::to_string(newObjs++).c_str()); // copy the number part
    printf("Creating %s", name);
    Add(name, object);                                                                         // add it to our map
}

If I iterate over every item from the map, the pair appears to exist and works indexing it but when I index it manually (GameObjects["pairName"]) the program crashes with a segmentation fault message. Also GameObjects.contains("pairName") returns false even if I added the pair with that name.

I use GCC 11.2.0 on Ubuntu with the C++20 standard enabled.

Answer 1

A string literal has a different pointer value to a return value of malloc. The map will do lookup with std::less<const char *> which compares pointer values, it does not compare text.

Use std::string, and don't use malloc or owning raw pointers.

std::map<std::string, std::unique_ptr<GameObject>> GameObjects;

void myClass::Add(std::string name, std::unique_ptr<GameObject> object)
{
    GameObjects.emplace(std::move(name), std::move(object));
}

void myClass::Instantiate(std::unique_ptr<GameObject> object)
{
    std::string name{ "New Object " };
    name += std::to_string(newObjs++)
    std::cout << "Creating " << name;
    Add(std::move(name), std::move(object));                                                                         
}