CODEWITHSUNDEEP
c++
Argon P.
Argon P.

Reputation: 23

problem in #defining cout?

A friend of mine told me that this code has some problems:

#include <iostream>
#include <cstdio>
using namespace std;
#define cout printf   
int main(){
    cout("cout");
}

He didn't give me the reason and asked me to figure it out which I couldn't. The code seems to be working fine, what could possibly be wrong with it?

Upvotes: 0

Views: 615

Answers (5)

Prasoon Saurav
Prasoon Saurav

Reputation: 92864

As far as I know the Standard forbids defining names (with #define) declared in any standard library header.

Found this in n3290 ($17.6.4.3.1)

17.6.4.3.1 Macro names [macro.names]

1 A translation unit that includes a standard library header shall not #define or #undef names declared in any standard library header.

Upvotes: 11

bdonlan
bdonlan

Reputation: 231163

You have declared main as returning int, but have not included a return statement. You should add a return 0; to the end of the main function. In C++ you don't have to return a value from main, but it's good style.

Oh, and don't #define cout printf, it's really confusing. It may not be technically illegal, but it's not nice for whoever comes later to try to maintain your code.

Upvotes: 0

Sarfaraz Nawaz
Sarfaraz Nawaz

Reputation: 361472

Yes. It has problem.

Since its C++, one may habitually write cout << 1000 which would be an error in this case, but which is otherwise very normal in C++.

What next? Are you trying to define this:

#define scanf cin

//so that you can use it as
scanf >> variable; //not so kewl.

My advice is :

Don't try to change the meaning of such names. What will you get by doing so, after all? Nothing.

Upvotes: 2

johnsyweb
johnsyweb

Reputation: 141810

While you may argue that this code "seems to be working fine", consider a few years down the line when your 7-line source file is a 7-hundred-line source file and you are not the only maintainer.

You've moved on from writing C-style printf statements in C++ source files and you add (or another maintainer adds) the following line of perfectly valid C++:

    cout << "What is wrong with my perfectly valid C++ code? " << endl;

And your compiler reports:

test.cpp:699: error: invalid operands of types ‘int ()(const char*, ...)’ and ‘const char [29]’ to binary ‘operator<<’

A whole world of pain!

Upvotes: 2

Ben Voigt
Ben Voigt

Reputation: 283664

It's got maintenance problems, because you'd redefined well-known features to work differently. So no other programmer will want to work on this code.

Similar:

#define MULTIPLY(a, b) (a + b)

#define FIVE 12
#define THREE 3

int main(void)
{
    return MULTIPLY(FIVE, THREE);
}

It gives the right answer, but is totally unmaintainable.

Upvotes: 1

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