Can a C function have multiple signatures?

Question

Possible Duplicate:
function overloading in C

Apologies if this is a dup but if it is, I can't find it.

In C, can you define multiple functions with the same function name, but with different parameters? I come from a C# background. In C#, the following code is completely legal.

//Our first function

int MyFunction()
{
    //Code here
    return i;
}

int MyFunction(int passAParameter)
{
    // Code using passAParameter
    return i;
}

In my specific case, I would like to create a function that has one optional parameter (that is an int) at the end of the parameter list. Can this be done?

No, sir function overloading is not allowed in C but it is allowed in C++. — Khaled Alshaya, Sep 30 '11 at 18:44
It's called function overloading. Look here: http://stackoverflow.com/questions/479207/function-overloading-in-c — Matjaz Muhic, Sep 30 '11 at 18:44
While the similar question in the link might have some hints on doing some sorts of overloading, you probably should stay away from it. Unlike C#, overloading is not idiomatic in C and it is perfectly acceptable to create two functions `MyFunction` and `MyFunctionWithParameter` — hugomg, Sep 30 '11 at 18:53
Since this is closed I can not give you an "answer" but have to put this in a comment. The special case of optional parameters is possible to do with macro tricks. Have a look into P99, http://p99.gforge.inria.fr/ — Jens Gustedt, Sep 30 '11 at 19:47

score 55 · Accepted Answer · answered Sep 30 '11 at 18:43

55

No. C does not support overloading.

answered Sep 30 '11 at 18:43

James McNellis

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Whereas C has no overloading in general, the special case that OP asks for namely default arguments, can be done with macros in a convenient way. – Jens Gustedt Sep 30 '11 at 19:49
2

If you want to see how it's supported in C++, use the `nm` tool on unix-like OSs and you will see that the symbols built into ELF in C++ get mangled and have their type information added into the symbol name. If you ```extern "C"``` around the same symbols and build again and look, you'll noticed that the names are not mangled to include the argument types. – zjm555 Sep 09 '14 at 17:27

score 10 · Answer 2 · answered Sep 30 '11 at 18:45

No. In strict C, you cannot do overloading.

However, given that most C compilers also support C++, and C++ does support overloading, there's a good chance you can do overloading if you're using a mainstream C/C++ compiler.

But its not strictly standard or portable to pure-C environments.

score 3 · Answer 3 · answered Sep 30 '11 at 18:43

3

No you must use a different name for each function (this is not true with C++, as it allows you to specify optional parameters)

answered Sep 30 '11 at 18:43

Foo Bah

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Can a C function have multiple signatures?

3 Answers3