CODEWITHSUNDEEP
c++staticsingleton
user10463779
user10463779

Reputation:

Exception thrown: read access violation. _Scary was nullptr

Trying to learn to code using Jim Horton's Beginning C++ Programming with Jim Horton. It's crashing with the following:

ZombieArena.exe!std::_Tree<std::_Tmap_traits<std::string,sf::Texture,std::less<std::string>,std::allocator<std::pair<std::string const ,sf::Texture>>,0>>::_Find_lower_bound<std::string>(const std::string & _Keyval) Line 1704    C++
ZombieArena.exe!std::_Tree<std::_Tmap_traits<std::string,sf::Texture,std::less<std::string>,std::allocator<std::pair<std::string const ,sf::Texture>>,0>>::_Find<std::string>(const std::string & _Keyval) Line 1457    C++
ZombieArena.exe!std::_Tree<std::_Tmap_traits<std::string,sf::Texture,std::less<std::string>,std::allocator<std::pair<std::string const ,sf::Texture>>,0>>::find(const std::string & _Keyval) Line 1466  C++
ZombieArena.exe!TextureHolder::GetTexture(const std::string & filename) Line 21 C++
ZombieArena.exe!Zombie::spawn(float startX, float startY, int type, int seed) Line 28   C++

The code for this is:

    #pragma once

#ifndef TEXTURE_HOLDER_H
#define TEXTURE_HOLDER_H
#include <SFML/Graphics.hpp>
#include <map>

using namespace sf;
using namespace std;

class TextureHolder
{
private:
    // A map container from the STL,
    // that holds related pairs of String and Texture
    map< string, Texture> m_Textures;
    // A pointer of the same type as the class itself
    // the one and only instance
    static TextureHolder* m_s_Instance;
public:
    TextureHolder();
    static Texture& GetTexture(string const& filename);
};
#endif

The cpp file is:

    #include "TextureHolder.h"

// Include the "assert feature"
#include <assert.h>

TextureHolder* TextureHolder::m_s_Instance = nullptr;
TextureHolder::TextureHolder()
{
    assert(m_s_Instance == nullptr);
    m_s_Instance = this;
}

Texture& TextureHolder::GetTexture(string const& filename)
{
    // Get a reference to m_Textures using m_s_Instance
    auto& m = m_s_Instance->m_Textures;
    // auto is the equivalent of map<string, Texture>
    // Create an iterator to hold a key-value-pair (kvp)
    // and search for the required kvp
    // using the passed in file name
    auto keyValuePair = m.find(filename);
    // auto is equivalent of map<string, Texture>::iterator
    // Did we find a match?
    if (keyValuePair != m.end())
    {
        // Yes
        // Return the texture,
        // the second part of the kvp, the texture
        return keyValuePair->second;
    }
    else
    {
        // File name not found
        // Create a new key value pair using the filename
        auto& texture = m[filename];
        // Load the texture from file in the usual way
        texture.loadFromFile(filename);
        // Return the texture to the calling code
        return texture;
    }
}

It crashes on the 2nd auto line for the map find. Any ideas???? I'm confused. Thanks in advance.

Upvotes: 0

Views: 2503

Answers (2)

SZYoo
SZYoo

Reputation: 437

I also encountered a similar problem. It seems to be a BUG of the compiler. See here https://developercommunity.visualstudio.com/t/Exception-thrown:-read-access-violation/10666202?sort=newest&viewtype=solutions.

My solution is declare a static function in TextureHolder.cpp in which there is a static instance defined, and the function returns the instance.

TextureHolder& GetGlobalInstance()
{
    static map< string, Texture> g_Textures;
    return g_Textures;
}

Upvotes: 0

Alex FunnyWL
Alex FunnyWL

Reputation: 1

Add in the main:

// Here is the instance of TextureHolder
TextureHolder holder;

Upvotes: 0

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