用于创建对象的Constexpr [英] Constexpr for creating objects

问题描述

我试图找出使用 constexpr 创建对象（而不是正常创建对象）是否会提高性能。

I'm trying to figure out if there is a performance gain of creating objects with constexpr instead of normally.

这是 constexpr 的代码段。

class Rect
{
    const int a;
    const float b;
public:
    constexpr Rect(const int a,const float b)
    : a(a),b(b){}
};

int main()
{
     constexpr Rect rect = Rect(1,2.0f);
}

并且没有 constexpr

class Rect
{
    int a;
    float b;
public:
    Rect(int a, float b)
    : a(a),b(b){}
};

int main()
{
    Rect rect = Rect(1,2.0f);
}

我期望 constexpr ，因为应该在编译时初始化内存。

I was expecting there will be a lot less code for constexpr since the memory should be initialized at compile-time.

我使用 constexpr 正确吗？如果不是这样，可以使用 constexpr 在编译时创建对象，然后在没有任何运行时开销的情况下使用它们吗？

Am I using constexpr properly? And if that is not true, can you use constexpr to create the objects at compile-time and then use them without any runtime overhead?

谢谢！

推荐答案

事实证明，我包含一些标头，这些标头负责代码。

It turned out that I had some headers included which were responsible for the similarity of the code.

答案是两种情况之间有很大差异。

The answer is that there is a big difference between both cases.

在没有优化的情况下进行编译时，生成的代码中存在实质性差异 ...
-cdhowie

When compiling without optimizations, there is a substantial difference in the generated code... -cdhowie

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