Is C a Object oriented language...?

[tyagithehacker]

C is basically a non-object oriented language, then while doing system programming in UNIX why we have two different versions of OPEN function (system call):

 int open(const *pathname, int flags);
int open(const *pathname, int flags, mode_t mode);

which is basically a populer feature called Function Overloading of object oriented language only.

[whodgson]

Many people say that C is a subset of C++. Some say that C++ is a subset of C. It would seem that UNIX system is playing it safe in overloading the open() function.

[Banfa]

@whodgson
I'm not sure that I have heard anyone say the second. C and C++ are most like siblings with the same parent. C++ supports a lot but not all of the C standard, C definitely doesn't support all of the C++ standard.

The posted code snippet is not C and will not compile with C. C does not support function overloading and produces these diagnostics

2: error: conflicting types for 'open'
1: note: previous declaration of 'open' was here

Additionally no type is given for pathname.

[tyagithehacker]

@Banfa
TO BENFA,

thanx for your reply, but that code is not a part of any executable, it is just the way open() function has been prototyped in unix. and one can use any one of the function as per the requirment, that too without any error.

actually what i was asking is that why there are two diffrent flavours of open() function, even when we doing system programming in UNIX under C language.

[tyagithehacker]

C is basically a non-object oriented language, then while doing system programming in UNIX why we have two different versions of OPEN function (system call):

 int open(const *pathname, int flags);
int open(const *pathname, int flags, mode_t mode);

which is basically a popular feature called Function Overloading of object oriented language only.

[Banfa]

No you have mis understood. it is not possible for those 2 prototypes to appear in a C program without causing an error because C does not support function overloading.

If those 2 prototypes appear in the same header which is used for a C compilation then there must be some mechanism that is disabling one of them, conditional of a preprocessor signal for instance or they exist in different header files in which case you can only include one of those 2 headers.

Because what you have presented is impossible either the question you have asked is based on some falsehood somewhere (i.e. those 2 prototypes do not actually exist) or you have not provided the context that explains how those 2 prototypes can exist.

If it is the second case then it is that context that will explain why there are 2 flavours of open.

[Banfa]

It would have helped if you had mentioned that you where quoting documentation and not code. It would also have helped if having quoted documentation you had also gone on and read it all.

Here is the documentation for open, read it, it will answer your question.

As it happens open is actually prototyped as a varidac function allowing the 3rd parameter to be optional.

[tyagithehacker]

@Banfa
hmm it was much clear this time.
thanx a lot... :-)

[SinTak]

It is not function overloading. C allows variadic arguments, so that you can have a function with one or more arguments. The function called is always the same, but it can be aware of the fact that there must be a third argument, and pick it. In the "open" case, it depends on "flags" argument. If you use O_CREAT, and you don't provide the third argument, the compiler can't complain, while the function "thinks" that there's a third argument, and strange "undefined behaviour" things can happen (likely you get a "random" mode for your created file).

[numberwhun]

You need to post your questions in the correct forum. There is a C/C++ forum, that is where this question should have been asked.

I am moving this question there, but please be mindful of where you are posting in the future.

Regards,

Jeff

[Banfa]

Note since both threads on this subject have ended up in C++ I have merged them