面向对象的概念是否适用于C语言？

Question

In C#, we learned that function overloading occurs when more than one function have the same identifier but different signature.

Although the concept of function overloading is specific to object-oriented languages, is it applicable to the C language as well on the basis of the following observation?

printf("%d", 3);

printf("%d + %d = %d", 1 , 2 , 3 );

The first printf passes only TWO arguments. The second printf passes FOUR arguments.

Does that mean printf is overloaded?

Answer 1

No printf is not overloaded. There is no function overloading or any other object oriented goodness in C. The way printf works is by using argument list. Take a look at this article http://www.cprogramming.com/tutorial/c/lesson17.html

Answer 2

The printf family of functions does not use overloading, but rather take a variable number of arguments.

Function overloading and overriding (ie virtual methods in C#) are not supported in C, which doesn't even have member functions.

However they can be imitated by means of function pointers. This is the approach taken for instance in the implementation of the X Window System.

Answer 3

Read about variadic functions .

printf and scanf family of functions are variadic functions.

Useful Links:

1. Cprogramming.com

2. Writing Variadic Functions

To complete the answer: C does not support Function Overloading.

Answer 4

No printf is not an example for function overloading as others already stated, it uses the features from stdarg.h . But seemingly unknown to many, C has some sorts of function overloading.

• since C99 C has "type generic mathematical functions" in tgmath.h that have you eg compute float or double sin depending on the argument that you are passing
• since C11 has _Generic , a feature that is even more powerful than function overloading, and that can be used, among other things, to write function-like macros that implement overloading features

And, all of this has nothing to do with OO programming.

Answer 5

Function overloading is language feature completely separate from object-oriented design. Just because it tends to exist in languages that have OO features, doesn't make it an OO feature as well.

The corner stones of OO design are: autonomous classes with limited dependences towards the outside world ("loose coupling"), private encapsulation of data/methods and inheritance/polymorphism.

Every other feature that doesn't fit in with the above is just some extra fluff. Function overloading and operator overloading are two such fluffy things - there are many OO languages that don't support those 2 features.

As for printf , it uses the icky variable argument feature of the C language. I wouldn't call that function overloading, but rather some old ad hoc crap that was introduced in the 70s just so that C could brag about having variable number of arguments. A feature which is mildy useful, to say the least. It isn't used in any sane, production-quality code.