The following are English question and answer titles generated based on the article content you provided: Why does `char` behave differently from integer types in template instantiation when comparing `char`, `signed char`, and `unsigned char`?

differences in behavior between char, signed char and unsigned char

The code below compiles successfully, but char behaves differently than integer types.

cout << getIsTrue< isX<int8>::ikIsX  >() << endl;
cout << getIsTrue< isX<uint8>::ikIsX  >() << endl;
cout << getIsTrue< isX<char>::ikIsX  >() << endl;

The result is three instantiation patterns for three types: int8, uint8 and char. Why does this happen?

The same is not true for integers: int and uint32 result in one pattern instantiation, and signed int results in another.

The reason is probably because C treats char , signed char and unsigned char as three different types. While int is the same as signed int. Is this true or am I missing something?

<code class="cpp">#include <iostream>

using namespace std;

typedef   signed char       int8;
typedef unsigned char      uint8;
typedef   signed short      int16;
typedef unsigned short     uint16;
typedef   signed int        int32;
typedef unsigned int       uint32;
typedef   signed long long  int64;
typedef unsigned long long uint64;

struct TrueType {};
struct FalseType {};

template <typename T>
struct isX
{
   typedef typename T::ikIsX ikIsX;
};


// Это  int==int32 неоднозначно
//template <>            struct isX<int  >    { typedef FalseType ikIsX; };  // Ошибка
template <>            struct isX<int32  >  { typedef FalseType ikIsX; };
template <>            struct isX<uint32 >  { typedef FalseType ikIsX; };


// Почему это не двусмысленно? char==int8
template <>            struct isX<char  >  { typedef FalseType ikIsX; };
template <>            struct isX<int8  >  { typedef FalseType ikIsX; };
template <>            struct isX<uint8 >  { typedef FalseType ikIsX; };


template <typename T> bool getIsTrue();
template <>           bool getIsTrue<TrueType>() { return true; }
template <>           bool getIsTrue<FalseType>() { return false; }

int main(int, char **t )
{
   cout << sizeof(int8) << endl;  // 1
   cout << sizeof(uint8) << endl; // 1
   cout << sizeof(char) << endl;  // 1

   cout << getIsTrue< isX<int8>::ikIsX  >() << endl;
   cout << getIsTrue< isX<uint8>::ikIsX  >() << endl;
   cout << getIsTrue< isX<char>::ikIsX  >() << endl;

   cout << getIsTrue< isX<int32>::ikIsX  >() << endl;
   cout << getIsTrue< isX<uint32>::ikIsX  >() << endl;
   cout << getIsTrue< isX<int>::ikIsX  >() << endl;

}

I'm using g 4.something

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