gcc and "Hello World" (in C++)

[OldAl]

Hi,

I have just returned to coding C++ after a long break away from any programming. As is customary, I am trying to start with the "hello world" "program". I need to use gcc and am trying it. I expect it to recognise the code as C++ and use the appropriate front-end.

I am using openSUSE10.3 on an amd64 dual core computer. The compilation fails -- and that makes me feel really, really miserable. Here is the code. At the end of it, I add the dialog of gcc attempted compilation, as a comment to the code.

#include <iostream>

//hello.cpp

int main()
{
  cout << 'Hello world!\n';
  return 0;
}
/*
ak@amd64:~/gcc> gcc hello.cpp -o hello
hello.cpp:7:11: warning: character constant too long for its type
hello.cpp: In function ‘int main()’:
hello.cpp:7: error: ‘cout’ was not declared in this scope
ak@amd64:~/gcc>
*/

I would be most grateful for any suggestions, including a recommendation of a good elementary text on C++ and URLs of any other forums that may be helpful.

Regards,
OldAl.

[kakariko81280]

chris@angua:~/dev/hello$ cat hello.cpp
#include <iostream>
using namespace std;

//hello.cpp

int main()
{
  cout << "Hello world!\n";
  return 0;
}
chris@angua:~/dev/hello$ g++ hello.cpp -o hello
chris@angua:~/dev/hello$ ./hello
Hello world!
chris@angua:~/dev/hello$

Add 'using namespace...' or use 'std::cout' and use double quotes around the string.

All hints to my also rusty c++ were taken from this c++ tutorial site

Let us know how you get on,

Chris...

[OldAl]

[code]chris@angua:~/dev/hello$ cat hello.cpp
[...]
Add 'using namespace...' or use 'std::cout' and use double quotes around the string.

All hints to my also rusty c++ were taken from this c++ tutorial site

Let us know how you get on,

Chris...

Chris,

Many thanks for your reply and the information. In particular, the link to the c++ tutorial site will be usefull.

The "hello program" was copied from a book, albeit with "replacement" of double quotes with single quotes, which was all my own doing in desperation...

When I corrected the quotes and added "using namespace", the "hello program" worked ok when compiled with g++, but it still fails if I use gcc instead of g++. Strange...

I will read the tutorial that you have referred me to.

Also, I will mark this forum as a great reference, thanks to you!

OldAl.

[drl]

Hi.

... When I corrected the quotes and added "using namespace", the "hello program" worked ok when compiled with g++, but it still fails if I use gcc instead of g++. Strange...

If your problem was with linking, then perhaps this will explain it:

Compiling C++ Programs

C++ source files conventionally use one of the suffixes .C, .cc, .cpp,
.c++, .cp, or .cxx; preprocessed C++ files use the suffix .ii. GCC
recognizes files with these names and compiles them as C++ programs
even if you call the compiler the same way as for compiling C programs
(usually with the name gcc).

However, C++ programs often require class libraries as well as a com-
piler that understands the C++ language---and under some circumstances,
you might want to compile programs from standard input, or otherwise
without a suffix that flags them as C++ programs. g++ is a program
that calls GCC with the default language set to C++, and automatically
specifies linking against the C++ library.
-- man gcc

You can try compiling and omit the linking by using "-c" with gcc, if that seems to compile your code correctly, then the problem was with the library selection ... cheers, drl

[OldAl]

Hi "drl",

Hi.
[...]
You can try compiling and omit the linking by using "-c" with gcc, if that seems to compile your code correctly, then the problem was with the library selection ... cheers, drl

I followed your advice and compiled with gcc with -c switch. It did compile. As you pointed out, this suggests that a library is missing.

Yet the man gcc says that g++ calls gcc with identification of the program being C++. And g++ **does** compile and link producing code that works. I am bushed.

Thank you for your help - great to get these hints here!

OldAl.

[drl]

Hi.

The libraries are missing in the sense that they were not selected in the linking phase when one uses gcc. Using g++ will cause those extra, appropriate libraries to be selected and so the link phase will be successful.

With some work you could find those extra libraries and continue to use gcc, but it's less bother simply to use g++ ... cheers, drl

[OldAl]

Hi drl,

Hi.

The libraries are missing in the sense that they were not selected in the linking phase when one uses gcc. Using g++ will cause those extra, appropriate libraries to be selected and so the link phase will be successful.

With some work you could find those extra libraries and continue to use gcc, but it's less bother simply to use g++ ... cheers, drl

I think you are absolutely right - on both counts. I should drop (temporarily) my obsession with gcc and just use g++ and work through the tutorial, mentioned in the first reply to this thread. My interest in gcc came from a KDE project (kmymoney), whose mailing list I subscribed to some years back.

Parallel to using g++, I think it would be worth while to have a look at the "Make" files of that project and see how the developers invoke gcc.

Thanks for all your help. It is great to have the horse that pulls my cart to be turned in the right direction!

Very gratefully,
OldAl.