C++ Programming Questions by vector<Object *> use and new Object() - c++

Question

im really stuck right now...
Summary:
My C++ application crashes every time with an
Access Violation Reading Error on location 0x000000008
which must be an error by the use of multiple vectors of object pointers
where the objects are created with the new statement.
-------------
I want to train my skills by creating a simple GUI Engine with SDL2
and designed it like this:
Create Engine class/object with extern (global)
Because i want to pack all Engine related stuff like update functions
in one packet and init this via a init function:
Create GUI class/object with extern
I wanted this to also be in one "pack" and inside this class
i have multiple std::vector <#PointerToObject#> to keep
my created window objects alive on th global heap instead
of creating them temporary is this correct or is there a better
method to do so?
GUI.h
//...
class GUIWindow
{
//...
std::vector< GUIGadgetLable* > _guiGadgetLables;
std::vector< GUIGadgetButton* > _guiGadgetButtons;
//...
};
class GUI
{
//...
std::vector< GUIWindow* > _guiWindows;
//...
void createWindow(std::string title, int x, int y, int sx, int sy);
};
//...
extern GUI engineGUI;
GUI.cpp
//...
void GUI::createWindow(std::string title, int x, int y, int sx, int sy)
{
this->_guiWindows.insert(this->_guiWindows.end(), new GUIWindow(title,x,y,sx,sy));
return this->_guiWindows.at(this->_guiWindows.size()-1);
}
//...
GUI engineGUI;
I do this in many objects and my hirachy for GUI creation is like this:
GUI
1>GUIWindow
2->GUIGadgetLable
3-->GUIText
4--->ResourceTexture (createFromText)
2->GUIImage
3-->ResourceTexture (createFromFile)
2->GUIGadgetButton
3-->GUIText
Everything worked fine till i implemented my ResourceManager to capsule
the SDL texture rendering functions like load a Bitmap from a file into an SDL_Texture and create a texture from a text.
ResourceManager.h
class ResourceFont
{
public:
TTF_Font* _font = NULL;
int _fontSize = 3;
std::string _fontFile = "";
bool loadFromFile(std::string file, int fSize);
void destroy();
};
class ResourceTexture
{
public:
SDL_Texture *_texture = NULL;
SDL_Rect _size;
SDL_Rect _position;
std::string _data = ""; //File/Text
bool _visible = true;
bool _isText = false;
int _fSize = 3;
SDL_Color _textColor = {70,30,120};
bool createFromFile(std::string file, int x, int y, float sx, float sy);
bool createFromText(std::string text, int fSize, int x, int y, SDL_Color foreGround);
bool changeText(std::string text);
void resize(float sx, float sy);
void update(int x, int y);
void draw();
void destroy();
};
class ResourceManager
{
public:
std::vector< ResourceFont* > _resourceFonts;
std::vector< ResourceTexture* > _resourceTextures;
TTF_Font* addFont(std::string fontFile, int fSize);
};
extern ResourceManager engineResource;
The Texture things worked completely but after the implementation of the ResourceFont* Vector and the addFont Function (which uses TTF_Font to create a new font handle for the ResourceTexture::createFromText function) which is below the Program crashes with an access violation reading at adress 0x0...08 and this at the point where i call the
new ResourceFont()
or
return this->_resourceFonts.at(i)->_font;
in my code so i think i got my heap corrupted but i dont know why if everything with the same methods worked well until this point?
ResourceManager.cpp
TTF_Font *ResourceManager::addFont(std::string fontFile, int fSize)
{
std::cout << "GOIN "<< fSize << std::endl;
if (this->_resourceFonts.size())
{
for (unsigned int i=0; i < this->_resourceFonts.size(); i++)
{
std::cout << "Compare: " << i << " Search: " << fSize << " Found: " << this->_resourceFonts.at(i)->_fontSize << std::endl;
if (this->_resourceFonts.at(i)->_fontSize==fSize) //this->_resourceFonts.at(i)->_fontFile==fontFile&&
{
//std::cout << this->_resourceFonts.at(i) << std::endl;
if (this->_resourceFonts.at(i)->_fontSize==fSize)
{
std::cout << "Found one " << &this->_resourceFonts.at(i)->_font << std::endl;
return this->_resourceFonts.at(i)->_font; //Crashes sometimes here were it try to acces the object
}
else
{
return 0;
}
}
std::cout << "Nope" << std::endl;
}
}
std::cout << "Create One" << std::endl << std::endl;
this->_resourceFonts.insert(this->_resourceFonts.end(), new ResourceFont()); //Crashes sometimes here
this->_resourceFonts.at(this->_resourceFonts.size()- 1)->loadFromFile(fontFile,fSize);
if (this->_resourceFonts.at(this->_resourceFonts.size()-1)->_font)
{
return this->_resourceFonts.at(this->_resourceFonts.size()- 1)->_font;
}
else
{
this->_resourceFonts.at(this->_resourceFonts.size()- 1)->destroy();
return NULL;
}
}
Have anybody an idea how to solve this?
Thank you :)

Answer 1

Don't know if this is the real error, but the code is too large to fit in a comment.
At the very end of AddFont you have:
if (this->_resourceFonts.at(this->_resourceFonts.size()-1)->_font)
{
return this->_resourceFonts.at(this->_resourceFonts.size()- 1)->_font;
}
else
{
this->_resourceFonts.at(this->_resourceFonts.size()- 1)->destroy();
return NULL;
}
This code tests for a non-null _font, which means that in the else part the _font member is null. And it is still left in the _resourceFonts vector.

Answer 2

It looks like i found the Problem:
If i use the ResoruceManager::addFont() direct in every function instead of saving it in an extra TTF_Font* var the program runs normal.