c++，真有趣啊

由于笔者的水平不太行，在这个贴里记录一些自己犯过的不太容易被发现的错误

20221029

基类

class CBase
{
public:
    virtual ~CBase() {}

private:
    virtual bool __fooV() { return true; }

    friend class CFactory;
};

继承类

class CDerived : public CBase
{
private:
    virtual bool __fooV(int x) { return x > 100; }

    friend class CFactory;
};

工厂类

class CFactory
{
public:
    template <typename TDerived, class... TArgs>
    requires std::is_base_of<CBase, TDerived>::value
    static TDerived* createResource(TArgs&&... vArgs)
    {
        TDerived* pDerived = new TDerived();
        assert(pDerived);

        CBase* pBase = pDerived;

        bool IsInitSucceed;
        if (sizeof...(vArgs) > 0) IsInitSucceed = pDerived->__fooV(std::forward<TArgs>(vArgs)...);
        else                      IsInitSucceed = pBase->__fooV();

        if (!IsInitSucceed)
        {
            delete pDerived;
            pDerived = nullptr;
        }

        return pDerived;
    }
};

CDerived* pDerived = CFactory::createResource<CDerived>();

期望：在函数 CFactory::createResource 的实例化中，由于模板参数包的大小为0，所以最后当然会执行else分支的部分，那么不管if部分的话，编译肯定是能顺利通过的吧？

事实：编译的时候可不会管哪些函数会不会被执行到，CBase::__fooV 对 CDerived 不可见，自然编译就失败了。

修改方法：在 CDerived 中override __fooV()

20230715

在OpenGL的Compability上下文中，绘制point sprite出错，在Fragment Shader中获取到的gl_PointCoord均为0

解决方案：在Compability上下文中需要调用 glEnable(GL_POINT_SPRITE)