CODEWITHSUNDEEP
c++staticcontainersaccess-violation
metablaster
metablaster

Reputation: 2184

Access violation when using static std::vector class member

Every 50th or so time I got access violation in my DLL implementing UI, mostly run time is just fine, I suspect this could be due to usage of static vector:

Here is code snapshot from class methods with stack trace:

BaseWindow.hpp

#define UI_API __declspec(dllexport)

class UI_API BaseWindow
    : public Object // base class for ref counting
{
     // the rest of the code...

protected:

    /** Register window class */
    [[nodiscard]] virtual bool RegisterCls(const WNDCLASSEX& wnd_class) const;

    /** fill in window class info struct */
    [[nodiscard]] virtual bool GetClsInfo(const PCTSTR& class_name, WNDCLASSEX& wnd_class) const;

     // the rest of the code...

};

BaseWindow.cpp

bool BaseWindow::GetClsInfo(const PCTSTR& class_name, WNDCLASSEX& wnd_class) const
{
    if (mhInstance) // handle to HINSTANCE
    {
        if (GetClassInfoEx(mhInstance, class_name, &wnd_class))
            return true;
        else return false;  // class does not exist, not an error

    }
    else // error handling
    {
        ShowError(Exception(GenericErrorCode::InvalidHandle, TEXT("Hinstance should not be nullptr")), ERR_BOILER);
        return false;
    }
}

bool BaseWindow::RegisterCls(const WNDCLASSEX& wnd_class) const
{
    WNDCLASSEX wcex{};

    // If the function does not find a matching class and successfully copy the data,
    // the return value is zero.
    if (!GetClsInfo(wnd_class.lpszClassName, wcex)) // calls above function!
    {
        // If the function fails, the return value is zero. 
        const ATOM atom = RegisterClassEx(&wnd_class);

        if (!atom) // error handling
        {
            ShowError(ERR_BOILER);
            return false;
        }
        else
        {
            ClassAtoms::AddClassAtom(atom); // call below function!
        }
    }

    return true;
}

ClassAtoms.hpp This is where problematic static vector is declared/defined

#define SUPPRESS(...) __pragma(warning(suppress : __VA_ARGS__))

class UI_API ClassAtoms
{   
     // the rest of the code...

public:
    /** Add registered window class to ATOM container */
    inline static void AddClassAtom(const ATOM& atom);

    // the rest of the class

private:
    /** Container for registered window classes */
    SUPPRESS(4251);  // needs to have dll-interface (inlining will result in internal compiler error)
    static std::vector<ATOM> mAtoms;

      // the rest of the code...
};

void ClassAtoms::AddClassAtom(const ATOM& atom)
{
    mAtoms.push_back(atom);
}

ClassAtoms.cpp

SUPPRESS(26426);  // Global initializer calls a non-constexpr function
std::vector<ATOM> ClassAtoms::mAtoms { };

And here is relevant stack trace:

Exception thrown at 0x00007FFA691212DE (vcruntime140d.dll) in TestUI.exe: 0xC0000005: Access violation reading location 0x000001A35C589000.

vcruntime140d.dll!memcpy_repmovs() Line 114 Unknown

UI.dll!std::_Copy_memmove(unsigned short * _First, unsigned short * _Last, unsigned short * _Dest) Line 1745 C++

UI.dll!std::_Uninitialized_move>(unsigned short * const _First, unsigned short * const _Last, unsigned short * _Dest, std::allocator & _Al) Line 1738 C++

UI.dll!std::vector>::_Emplace_reallocate(unsigned short * const _Whereptr, const unsigned short & <_Val_0>) Line 707 C++

UI.dll!std::vector>::emplace_back(const unsigned short & <_Val_0>) Line 659 C++

UI.dll!wsl::ui::BaseWindow::RegisterCls(const tagWNDCLASSEXW & wnd_class) Line 131 C++

UI.dll!wsl::ui::MainWindow::Initialize(HINSTANCE__ * hInstance, int x, int y, int width, int height, HWND__ * hParent, unsigned long dwStyle, unsigned long dwExStyle, HICON__ * hIcon, HMENU__ * hMenu) Line 68 C++

TestUI.exe!TestMainWindow(HINSTANCE__ * hInstance, HINSTANCE__ * hPrevInstance, wchar_t * lpCmdLine, int nCmdShow) Line 45 C++

[External Code]

Do you see any problem with this code, is my vector initialized properly if so then why push_back fails?

Upvotes: 0

Views: 1254

Answers (1)

darune
darune

Reputation: 10962

You could just use a meyer's singleton:

instead of:

static std::vector<ATOM> mAtoms;

make a function:

static auto& atoms() {
  static std::vector<ATOM> s;
  return s;
}

Now the vector is initialized on first use. This also affects static destruction order - which may or may not be an issue - but you should be aware of it.

Alternatively you could try with an inline initialization - this can likely move the init. up in init. order.

 static inline std::vector<ATOM> mAtoms;

and remove the .cpp init.

That being said, it is very likely that it is not that vector causing the heap corruption.

You need to debug heap corruptions. On windows a good start is _CrtSetDbgFlag

Upvotes: 1

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