Compare typedef is same type

Question

I am using C++ (not 11) and using some libraries which have different typedefs for integer data types. Is there any way I can assert that two typedefs are the same type? I\'

Answer 1

In C++11, you could use std::is_same::value.

Since you don't have C++11, you could implement this functionality yourself as:

template
struct is_same 
{
    static const bool value = false; 
};

template
struct is_same  //specialization
{ 
   static const bool value = true; 
};

Done!

Likewise you can implement static_assert¹ as:

template struct static_assert;
template<> struct static_assert {};  //specialization

Now you can use them as:

static_assert::value>(); //pass
static_assert::value>(); //fail

Or you could wrap this in a macro as:

#define STATIC_ASSERT(x)  { static_assert static_assert_failed; (void) static_assert_failed; }

then use as:

STATIC_ASSERT(is_same::value); //pass
STATIC_ASSERT(is_same::value); //pass

If you use macro, then you would see the following string in the compiler generated message if the assert fails:

static_assert_failed

which is helpful. With the other information in the error message, you would be able to figure out why it failed.

Hope that helps.

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^{1. Note that in C++11, static_assert is an operator (which operates at compile-time), not a class template. In the above code, static_assert is a class template.}