Having trtouble with C++ hello world, where are headers

Windows to Linux · 05-22-2009, 07:55 AM

Can any one tell me where gcc c++ header files are? Can't compile the Hello World

Nylex · 05-22-2009, 07:57 AM

Usually, somewhere under /usr/include. Can you tell us what the exact error messages are, please?

soleilarw · 05-22-2009, 08:18 AM

You have to make sure that you have the relevant development packages installed. Common libraries will be installed along with gcc, but other pieces like mysql will require you to install mysql-devel package to make the headers available. I'm sure that the compile error feedback gives enough information about the problem in your case.

Linux Archive

fantas · 05-22-2009, 11:31 AM

This sounds indeed like you're missing the development files. Under Ubuntu it's usually as simple as typing

Code:

sudo apt-get install build-essential

in a terminal, confirming and waiting for the installation to finish.

Windows to Linux · 05-23-2009, 10:53 AM

I found the lib, iostream, and everything seems OK
here is what I'm trying to compile

#include <iostream>
int main()
{
cout << "Hello world!\n";
return 0;
}

and gcc says

HI.cpp: In function 'int main()':
HI.cpp:4: error: 'cout' was not decared in this scope

jrecortel · 05-23-2009, 11:05 AM

Quote:

Originally Posted by Windows to Linux

I found the lib, iostream, and everything seems OK
here is what I'm trying to compile

#include <iostream>
int main()
{
cout << "Hello world!\n"
return 0;
}

and gcc says

HI.cpp: In function 'int main()':
HI.cpp:4: error: 'cout' was not decared in this scope

try this:

Code:

#include <iostream>
using namespace std;
int main()
{
cout << "Hello world!\n"
return 0;
}

or

Code:

#include <iostream>
int main()
{
std::cout << "Hello world!\n"
return 0;
}

norobro · 05-23-2009, 11:11 AM

Here's a bit of an explanation: link

Nylex · 05-23-2009, 11:25 AM

You're also missing a semi-colon on the line containing cout.

graemef · 05-23-2009, 08:04 PM

If you are still having problems then it could be that you are using gcc rather than g++ to compile your code.

Code:

#include <iostream>
int main()
{
std::cout << "Hello world!\n";
return 0;
}

And then assuming that your code is saved in a file called Hi.cpp try from the prompt

Code:

$ g++ -o Hi Hi.cpp
$ ./Hi

Windows to Linux · 05-25-2009, 11:14 AM

g++ is GCC, which can compile c++ code.

norobro · 05-25-2009, 12:02 PM

Quote:

Originally Posted by Windows to Linux

and gcc says

Not to speak for graemef, but the thought that you were using the c compiler crossed my mind because of the above statement. gcc is a link to the c compiler and g++ links to the c++ compiler, thus the confusion. But you would have gotten a lot of errors if you had been using gcc. Try it.

graemef · 05-25-2009, 09:41 PM

If you compile your program using plain old gcc it will look at the extension of the source code to determine the language and for *.cpp it will (by default) use c++. However it will not link in the C++ library and so you will need to explicitly link the library in. Whereas g++ forces the use of the C++ compiler on the source code and links in the C++ standard library.

Windows to Linux · 05-26-2009, 07:46 AM

Thanks for the help, using g++ worked