Can You Forward Declare a Typedef in C ?

Forward Declaration of a Typedef in C

In C , a forward declaration allows you to refer to a class or struct name before it's fully defined. This can be useful for situations like circular dependencies, where two header files need to include each other.

The question arises: can you also forward declare a typedef? The answer is yes, you can. However, there's a caveat. Unlike class or struct forward declarations, typedef forward declarations require the underlying type to be already forward declared.

To forward declare a typedef, follow these steps:

1. Forward declare the underlying type using the syntax: class/struct Name;.
2. Declare the typedef using the syntax: typedef Name NewName;.

For example:

class A;

typedef A B;

By following these steps, you can forward declare typedefs even though forward declarations normally apply to classes and structs. This can help minimize the inclusion tree and improve compilation speed.

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