CODEWITHSUNDEEP
c++templatestemplate-specialization
Tianyang Li
Tianyang Li

Reputation: 1785

Is it possible to prevent a C++ template being used without specialization?

Is it possible to prevent a C++ template being used without specialization?

For example, I have 

template<class T>
void foo() {}

And I don't want it to be used without being specialized for foo<int> or foo<char>.

Upvotes: 3

Views: 353

Answers (3)

SergV
SergV

Reputation: 1277

You can use undefined type in body of function. And you will get compile time error message:

template<class T> struct A;  
template<class T>  
void foo()  
{  
   typename A<T>::type a;  // template being used without specialization!!!
   cout << "foo()\n";  
}  
template<>  
void foo<int>()  
{  
   cout << "foo<int>\n";  
}  
template<>  
void foo<char>()  
{  
   cout << "foo<char>\n";  
}  
int main()  
{  
  foo<int>();  
  foo<char>();  
//  foo<double>();   //uncomment and see compilation error!!!
}

Upvotes: 1

Lily Ballard
Lily Ballard

Reputation: 185671

You should be able to declare the function without actually defining it in the generic case. This will cause a reference to an unspecialized template to emit an Undefined Symbol linker error.

template<class T>
void foo();

template<>
void foo<int>() {
    // do something here
}

This works just fine for me with clang++.

Upvotes: 8

rookiepupil
rookiepupil

Reputation: 39

It's possible when foo function have parameter. for example: template void foo(T param){} now, u can call foo(1), foo('c') without specializing.

Upvotes: -1

Related Questions