---
title: "Compiler Warning (level 1) C4308"
ms.date: "11/04/2016"
f1_keywords: ["C4308"]
helpviewer_keywords: ["C4308"]
ms.assetid: b3ed8d33-7ed9-4cf0-ae9a-d8af0a4dd8c6
---
# Compiler Warning (level 1) C4308
empty 'extern' : global destructor; no other 'extern'
The compiler detected the presence of no other global destructor function than an external function that was declared to be empty. This error can occur if, for example, a header file was included that declares the type of a function but no actual function is present in the corresponding file.
## Example
The following sample generates C4308:
```cpp
// C4308_c4308_1.cpp
// compile with: /c
class A {};
extern "C" void EmptyA() {} // extern function that is empty
class B : public A {
public:
B() {}
~B() {} // destructor is empty
};
```
The code causes C4308 because a declaration of the form `extern "C" void EmptyA()` defines an external function that is empty, but there is no actual implementation of the function in the corresponding file.
## See also
[Listed here](../code-quality/c4308.md)
[Empty 'extern'](../code-quality/c4308.md#c4308)
