C ++编译时检查函数参数 [英] c++ compile-time check function arguments

问题描述

我正在寻找一种在编译时检查函数参数的方法，如果可能的话，可以对编译器进行检查。

I'm searching a way to check function arguments in compile-time if it's possible to do for compiler.

更具体地说：

To be more specific: assume that we have some class Matrix.

class Matrix
{
    int x_size;
    int y_size;

public:
    Matrix(int width, int height):
        x_size{width},
        y_size{height}
    {}
    Matrix():
        Matrix(0, 0)
    {}
};

int main()
{
    Matrix a; // good.
    Matrix b(1, 10); // good.
    Matrix c(0, 4); // bad, I want compilation error here.
}

因此，在以下情况下，我可以检查或区分行为（函数重载吗？）

So, can I check or differentiate behavior (function overloading?) in case of static (source-encoded) values passed to function?

如果值不是静态的：

std::cin >> size;
Matrix d(size, size);

我们只能执行运行时检查。但是，如果值是在源中编码的呢？在这种情况下可以进行编译时检查吗？

we're only able to do runtime checks. But if values are encoded in source? Can I make compile-time check in this case?

编辑：我认为可以使用 constexpr构造函数，但是无论如何，无论有没有constexpr，都不允许重载。因此，无法以我想的方式解决问题。

I think this can be possible with constexpr constructor, but anyway overloading with and without constexpr isn't allowed. So problem can't be resolved in way I suppose.

推荐答案

要获取编译时错误，您需要一个模板：

To get a compile time error you would need a template:

template <int width, int height>
class MatrixTemplate : public Matrix
{
    static_assert(0 < width, "Invalid Width");
    static_assert(0 < height, "Invalid Height");
    public:
    MatrixTemplate()
    : Matrix(width, height)
    {}
};

（顺便说一句：我建议索引使用无符号类型）

(Btw.: I suggest unsigned types for indices)

如果没有static_assert（在此我切换为无符号）：

If you do not have static_assert (here I switch to unsigned):

template <unsigned width, unsigned height>
class MatrixTemplate : public Matrix
{
    public:
    MatrixTemplate()
    : Matrix(width, height)
    {}
};

template <> class MatrixTemplate<0, 0> {};
template <unsigned height> class MatrixTemplate<0, height> {};   
template <unsigned width> class MatrixTemplate<width, 0> {};

此处不支持空矩阵（MatrixTemplate< 0，0>）。但是，调整static_asserts或MatrixTemplate< 0类应该是一项容易的任务。 0>。

There is no support for empty matrices (MatrixTemplate<0, 0>), here. But it should be an easy task to adjust the static_asserts or class MatrixTemplate<0. 0>.

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