为每种类型编译时间typeid [英] compile time typeid for every type

问题描述

我想要一个 constexpr 函数，该函数将为我返回每种C ++类型的唯一ID，如下所示：

I'd like a constexpr function that will return me a unique id for every C++ type, something like this:

using typeid_t = uintptr_t;

template <typename T>
constexpr typeid_t type_id() noexcept
{
  return typeid_t(type_id<T>);
}

int main()
{
  ::std::cout << ::std::integral_constant<typeid_t, type_id<float>()>{} << ::std::endl;

  return 0;
}

但是我得到一个错误：

t.cpp: In function 'int main()':
t.cpp:23:69: error: conversion from pointer type 'typeid_t (*)() noexcept {aka long unsigned int (*)() noexcept}' to arithmetic type 'typeid_t {aka long unsigned int}' in a constant-expression
   ::std::cout << ::std::integral_constant<typeid_t, type_id<float>()>{} << ::std::endl;
                                                                     ^
t.cpp:23:69: note: in template argument for type 'long unsigned int' 

是否有解决方法或其他方法？

Is there a workaround or another way?

推荐答案

您可以使用如下所示的一些技巧答案。

You could use some tricks as shown in this answer.

甚至还有一个名为 ctti ，它应该可以立即使用

There's even a library called ctti that utilizes the same trick, it should work out of the box

static_assert(ctti::type_id<int>() != ctti::type_id<float>(), "compile-time type-id comparison");

constexpr auto hash = ctti::type_id<int>().hash();

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