#Trouble figuring out crash

157 messages · Page 1 of 1 (latest)

tardy sage
#

Thread 1 "r-type_client" received signal SIGSEGV, Segmentation fault. 0x0000000000484be0 in UIDGenerator::generate (this=0x50) at /home/aduthil/A3/B-CPP-500-PAR-5-1-rtype-maxime.eng/src/utils/UIDGenerator.cpp:18 18 unsigned int res = _uid;

class UIDGenerator {
    public:
        UIDGenerator();
        ~UIDGenerator();
        unsigned int generate();
    protected:
    private:
        unsigned int _uid = 0;
};

unsigned int UIDGenerator::generate() 
{             |
    //lign 18 v
    unsigned int res = _uid;

    _uid++;

    return res;
}
deep pumiceBOT
#

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fossil sail
#

intresting that that segfaults 🤔

#

how is your call for this? as in what code calls the generate

marble igloo
#

the call is on an invalid object

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so all members are at invalid addresses

fossil sail
#

yup that was where I wanted to go :)

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cause this code by itself is fine, so it has to be on the calling side pretty much

tardy sage
#

So it would be the UIDGenerator instance that doesn't exist

fossil sail
#

yup

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my guess is you have a UIDGenerator* somewhere

tardy sage
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    UIDGenerator _uidGen;

std::shared_ptr<GameObject> gameObject = std::make_shared<GameObject>(
            _game, _uidGen.generate(), name, position);
#

sadly not

#

it's just a regular instance

fossil sail
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🤔 odd

marble igloo
#

that says absolutely nothing about where the instance is

fossil sail
#

yup

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cause if it's right above the code that should be fine

tardy sage
# 
class GameObjectManager {
private:
    UIDGenerator _uidGen;
};
fossil sail
#

oh

#

yeah

tardy sage
#

and GameObjectManager does the previously mentionned call

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yeah what

fossil sail
#

🤔 and where does that other call happen

tardy sage
# 
std::weak_ptr<GameObject> addGameObject(std::string name, Vector3 position) {
        unsigned int uid = _uidGen.generate();
        std::shared_ptr<GameObject> gameObject = std::make_shared<GameObject>(
            _game, uid, name, position);
        _toBeAdded.push_back(gameObject);
        return gameObject;
    }
fossil sail
#

nah I thought to quickly about something but doesn't have to be true

tardy sage
#

I changed the call a bit to see if it changed anything

fossil sail
#

and addGameObject is a member function?

tardy sage
#

but still same error

#

yes

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btw the function works fine a few times

chrome skiff
tardy sage
#

then stops working for some reason

marble igloo
#

if the uidgenerator is invalid and part of the game object manager, the game object manager is invalid

tardy sage
# 
GameObject(Game &game, int uid, std::string name, Vector3 pos = {0, 0, 0}) : _game(game), _uid(uid), _name(name)
    {
        transform.setPosition(pos);
    }
fossil sail
#

but yeah, if it works a few times then im 99% sure the manager is 💀

tardy sage
# 
    GameObjectManager _goManager;

It's also an instance in another class

marble igloo
#

sure, how did you create that

fossil sail
#

cause since it's all local variables the lifetime of them is linked to well the class they are contained in lifetime

tardy sage
#

it's part of the Scene class

    Scene(Game &game) : _game(game), _goManager(game) {}
marble igloo
#

sure, where is that scene created

tardy sage
#

which is contained in the game instance

    std::vector<Scene> _scenes;
marble igloo
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and how is that populated

tardy sage
# 
    template<class SceneC = Scene>

void addScene() {
        _scenes.push_back(SceneC(*this));
    }
marble igloo
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SceneC?

tardy sage
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its a template

marble igloo
#

and why is it a template and the member isn't

tardy sage
#

member as in the vector ?

marble igloo
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cause your vector cannot store anything other than scene

fossil sail
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also just for reference you got a complete callstack for us?

marble igloo
#

yes, the member vector

tardy sage
tardy sage
marble igloo
#

would be simpler to run the thing through a sanitizer or a debugger

marble igloo
#

I'm pretty sure you were told so already

tardy sage
#

probably

marble igloo
#

you are forced into using pointers

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because the vector can only store base class instances

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derived instances are sliced and essentially unusable

fossil sail
#

yeah....

tardy sage
#

I guess it doesnt make sense in my head

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society just won't let me

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it's right there just store it

fossil sail
#

no sly is correct this is broken... 🤔

tardy sage
#

yeah they always are

fossil sail
#

you ever putting in another type of something that is not of type Scene? like a derived class?

marble igloo
#

an object is made of many parts

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a derived object is made of the base object(s) and additional stuff on top of that

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a vector only has enough space for exactly what you told the vector it had to store

tardy sage
#

I guess

marble igloo
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hence the weird term "slicing"

tardy sage
#

Well help appreciated i'll go fix my stuff

marble igloo
#

because when you attempt to assign a derived object to a base object, the extra part from the derived object is dropped/discarded

fossil sail
marble igloo
#

never said slicing was the root cause of the segfault, but the design is just flawed

fossil sail
#

fair enough, I thought you where implying that

tardy sage
#

sanity check:

        _scenes.push_back(std::make_unique<SceneC>(*this));

That's the right way to make a unique_ptr and to store it into a vector of said pointers

fossil sail
#

well depending on the type of scenes yes

tardy sage
# 
    std::vector<std::unique_ptr<Scene>> _scenes;
chrome skiff
tardy sage
#

I do not believe so

chrome skiff
marble igloo
#

unique_ptr to derived can be converted to unique_ptr to base so that's fine

fossil sail
#

this is somewhat fine it has a few issues though.... if there is a different constructor it will break, and if it's not a scene / derived type

marble igloo
#

but that's only for classes that derive from scene

tardy sage
# 
   private:
    Game &_game;
    GameObjectManager _goManager;
marble igloo
#

and only if the base class has a virtual destructor

tardy sage
#

fields of Scene

marble igloo
#

reference data members don't sound like a great idea if you're not sure what you're doing

chrome skiff
fossil sail
#

what should be fine tehcnically I suppose. But still debetable design wise

marble igloo
#

I assume _scenes is part of Game and the *this is what you initialize the reference with?

tardy sage
fossil sail
#

I have some idea but ima need a callstack for this 🤔
my guess would be there is some invalid pointer / reference to a scene somewhere where the call is generaterd

tardy sage
#

so I made a virtual scene destructor like sly said

class Scene {
   public:
    Scene(Game &game) : _game(game), _goManager(game) {}
    virtual ~Scene();
};

class RTypeGameScene : public Scene
{
public:
    RTypeGameScene(Game &game) : Scene(game)
     {
    }

    ~RTypeGameScene(){}

but I get
/usr/bin/ld: CMakeFiles/r-type_client.dir/src/main.cpp.o: in function Scene::Scene(Game&)':
/home/aduthil/A3/B-CPP-500-PAR-5-1-rtype-maxime.eng/include/Scene.hpp:13: undefined reference to vtable for Scene' /usr/bin/ld: CMakeFiles/r-type_client.dir/src/main.cpp.o: in function RTypeGameScene::RTypeGameScene(Game&)':
/home/aduthil/A3/B-CPP-500-PAR-5-1-rtype-maxime.eng/include/RTypeGameScene.hpp:12: undefined reference to vtable for RTypeGameScene' /usr/bin/ld: /home/aduthil/A3/B-CPP-500-PAR-5-1-rtype-maxime.eng/include/RTypeGameScene.hpp:12: undefined reference to Scene::~Scene()'
` at compile

fossil sail
#

did you implement it at all?

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or do you only have a definition?

tardy sage
#

By all do you mean the RTScene destructor ?

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cuz I modified the code to show the definition

fossil sail
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Yeah, right now you only showing definitions, are they actually implemented anywhere? And yeah the destructors

tardy sage
#

well the implementation is the {} part

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in my head atleast

fossil sail
#

Ah yeah my bad, missed that in the 2nd part, but the base?

tardy sage
#

I don't work with cpp files when figuring stuff out, makes it more cumbersome on the short term

fossil sail
#

ah allright 🤔 yes thats your issue then

tardy sage
#

well I didnt know it's needed

fossil sail
#

mark both of them as =default since they don't do anything

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for constructors and destructors that don't do anything use = default

tardy sage
#

I have a similar pattern for my components and my base class's destructor isnt defined

fossil sail
#

well that is wrongish

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cause you need to ensure the destructor of every object is properly called

tardy sage
#

well it still compiles

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so i'm not getting the full story of why it doesnt compile on the scene

fossil sail
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that doesn't mean it's correct ;)

tardy sage
#

(though implementing the base destructor did fix it )

fossil sail
#

cause in scene you mark it as virtual but the base class is never implemented

#

what here in this case is plain wrong

tardy sage
# 
class IComponent
{
public:
    IComponent(GameObject &gameObject, std::string name) : _gameObject(gameObject), _name(name)
    {
    }
    virtual ~IComponent();
#

I have the same thing in my IComponent

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that I store vectors of in the same way

fossil sail
#

do any other component actually implement a dtor?

tardy sage
#

no

fossil sail
#

there you go :)
propably why it compiles

tardy sage
#

If I remove my RTGameScene's destructor it still doesnt compile

fossil sail
#

why? well rather what error?

tardy sage
#

usr/bin/ld: CMakeFiles/r-type_client.dir/src/main.cpp.o: in function Scene::Scene(Game&)':
/home/aduthil/A3/B-CPP-500-PAR-5-1-rtype-maxime.eng/include/Scene.hpp:13: undefined reference to vtable for Scene' /usr/bin/ld: CMakeFiles/r-type_client.dir/src/main.cpp.o: in function RTypeGameScene::RTypeGameScene(Game&)':
/home/aduthil/A3/B-CPP-500-PAR-5-1-rtype-maxime.eng/include/RTypeGameScene.hpp:12: undefined reference to Scene::~Scene()' /usr/bin/ld: CMakeFiles/r-type_client.dir/src/main.cpp.o: in function RTypeGameScene::~RTypeGameScene()':
/home/aduthil/A3/B-CPP-500-PAR-5-1-rtype-maxime.eng/include/RTypeGameScene.hpp:9: undefined reference to Scene::~Scene()' /usr/bin/ld: CMakeFiles/r-type_client.dir/src/main.cpp.o:(.rodata._ZTI14RTypeGameScene[_ZTI14RTypeGameScene]+0x10): undefined reference to typeinfo for Scene'`

fossil sail
#

most likely cause the unique_ptr calls it :)

tardy sage
#

so I should have an implemented virtual destructor in the base class, and in the derived simply a destructor implementation ?

marble igloo
#

you have to define everything you declare

#

if there's nothing special to do you can use = default; as has already been mentioned

fossil sail
#

I think your base knowledge is lacking here:

#include <iostream>

struct base {
   virtual ~base() {std::cout << "~base\n";}      
};
struct derived : base {
   ~derived() {std::cout << "~derived\n";}        
};

int main()
{
    derived a;
}

~derived
~base

struct base {
   ~base() {std::cout << "~base\n";}      
};
struct derived : base {
   ~derived() {std::cout << "~derived\n";}           
};

int main()
{
    base* a = new derived();
    delete a;
}
~base

#include <iostream>

struct base {
  virtual ~base() {std::cout << "~base\n";}       
};
struct derived : base {
   ~derived() {std::cout << "~derived\n";}          
};

int main()
{
    base* a = new derived();
    delete a;
}
~derived
~base
marble igloo
#

I think you have typos in that last message

fossil sail
# 
#include <iostream>

struct base {
  virtual ~base() {std::cout << "~base\n";}      
};
struct derived : base {
   ~derived() {std::cout << "~derived\n";}         
};

int main()
{
    base a = derived();
}
~derived
~base
~base

another fun example with slicing ;)

fossil sail
tardy sage
#

I'm not sure any of that made it any clearer

marble igloo
#

well, you still must define everything you declared

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and you haven't done that

fossil sail
#

anyhow it would be good to carefully read those examples and their differences and their ouputs

marble igloo
#

the "undefined reference to vtable" is typically caused by you forgetting to define some of the virtual functions

#

which in short will be resolved if you actually defined everything properly

fossil sail
#

always implement declared function or mark them as =0

marble igloo
#

marking them as = 0; changes the semantics though

fossil sail
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yeah, it does but I figured it might be a bit out of scope to explain that now 😅

marble igloo
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I guess

fossil sail
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but yeah, TLDR non implemented but declared functions are a ticking timebomb for compile errors

tardy sage
#

Yeah I got the compilation down, now i'm banging my head against another wall

📎 message.txt
marble igloo
#

that's a weird terminology, usually it's declared but not defined

fossil sail
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I always mix them up in my head

marble igloo
#

well you dereferenced a nullptr

tardy sage
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oh I found my problem

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thanks

fossil sail
#

the entire problem or just this?

deep pumiceBOT
#

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