没有默认函数的C ++模板专业化 [英] C++ template specialization without default function

问题描述

我有以下代码编译和工作良好：

I have the following code that compiles and works well:

template<typename T>
T GetGlobal(const char *name);

template<>
int GetGlobal<int>(const char *name);

template<>
double GetGlobal<double>(const char *name);

但是我想删除default也就是说，我想调用GetGlobal< t>

However I want to remove the "default" function. That is, I want to make all calls to GetGlobal<t> where 't' is not an int or a double an error.

例如，GetGlobal< char>（）应该是一个编译时错误。

For example, GetGlobal<char>() should be a compile time error.

我试图删除默认函数，但是，如我想象的，我收到了很多错误..所以有一种方法来禁用它，并允许调用只有专门版本的函数？

I tried to just delete the default function, but, as I imagined, I received a lot of errors.. So is there a way to "disable" it and allow calls only to the specialized versions of the function?

谢谢！

推荐答案

编译时错误实现为：

template<typename T>
T GetGlobal(const char *name) { T::unimplemented_function; }
// `unimplemented_function` identifier should be undefined

如果使用Boost，它更优雅：

If you use Boost you could make it more elegant:

template<typename T>
T GetGlobal(const char *name) { BOOST_STATIC_ASSERT(sizeof(T) == 0); }

C ++标准保证没有这样的sizeof等于0的类型，得到编译时错误。

C++ Standard guarantees that there is no such type which has sizeof equal to 0, so you'll get a compile-time error.

由于 sbi 建议他的意见最后可以减少到：

As sbi suggested in his comments the last could be reduced to:

template<typename T>
T GetGlobal(const char *name) { char X[!sizeof(T)]; }

我喜欢第一个解决方案，因为它给出更清晰的错误消息（至少在Visual C ++中）比其他人。

I prefer the first solution, because it gives more clear error message (at least in Visual C++) than the others.

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