STL and Linux

Hi,

I am trying to port my current C++ and C skills to Linux Programming. I have successfully created the standard Hello World starting project in C for linux using both files and standard output.

I am trying to do something simular using standard C++ libraries, I tried to use the iostream template class in the STL library, I don't whether it is supported in Linux however I can seem to use #include <iostream> without a linking error being generated. The linker throughs an error "Undefined reference" when I write the complete Hello World program:

Code:

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#include <iostream>

using namespace std;

int main(void)
{
    cout << "\n Hello World";
}

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I am at the moment thinking the problem is that I am not linking the program with the required stl library, however I have no idea how to do this in Linux.

I have look through the standard included documentation but cannot find a reference of the libraries included in Linux (Red Hat 8.0), does any know of a good reference on the C++ libraries in Linux? Is this my problem or does Linux not support STL?

I am new to Linux programming so I am at the moment only really looking for a good reference site, thanks in advance.

KnNeeded

How are you building the system? Use g++ instead of gcc

Quote:

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Originally posted by cup
How are you building the system? Use g++ instead of gcc

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Well...gcc is the GNU compiler suite which provides frontends for C, C++, Java, Fortran etc. as well as these libraries. g++ is the traditional name of the C++ compiler which is part of the gcc suite...

So, I do not see what you mean?

There is not a library for the STL. The STL is (usually) only source code and exists entirely in the headers. It is called a library but there is not a library for it. At least not for the most popular implementations of the STL. The STL is part of the C++ language, so it is supported by the Linux compiler.

I have not used gcc much but I am nearly certain that what was said by cup is what you need and you probably already have the problem solved. As I recall, the default language that gcc recognizes is C and the default language that g++ recognizes is C++. They are essentially the same program except for minor differences such as that. I recall having a similar problem; in a Windows environment, I assumed that a file with a cpp extension would be compiled as a C++ program, but it was not. I got a compile error using gcc (I think) that went a way when I compiled using g++ (I think).

Quote:

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Originally posted by Andreas Masur
Well...gcc is the GNU compiler suite which provides frontends for C, C++, Java, Fortran etc. as well as these libraries. g++ is the traditional name of the C++ compiler which is part of the gcc suite...

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I am nearly certain that the default language for gcc is C.

Thanks Guys I will check it out

Do not pass void to functions in C++.

Sorry, I know that doesn't fix your problem but it is SO annoying when people do that =/

I'm wierd

Quote:

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Originally posted by Sam Hobbs
There is not a library for the STL. The STL is (usually) only source code and exists entirely in the headers. It is called a library but there is not a library for it. At least not for the most popular implementations of the STL.

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That is not true...one of the most popular STL implementation uses an library and/or a dll - STLport. I do not know much about others - Dinkumware, which is part of the IDE, might be different, however, I never used anything different than STLport...

Quote:

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Originally posted by Sam Hobbs
I am nearly certain that the default language for gcc is C.

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Well...gcc stands for GNU Compiler Collection, which simply acts as a front end for the underlying compilers it contains. The former name was GNU C Compiler, at that time it was only a simple C compiler...

Quote:

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Originally posted by Andreas Masur
That is not true...one of the most popular STL implementation uses an library and/or a dll - STLport. I do not know much about others - Dinkumware, which is part of the IDE, might be different, however, I never used anything different than STLport...

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I am quite surprised that this is the first time I have heard of STLport and that it uses libraries. I have seen Dinkumware mentioned in the C++ language newsgroup but not STLport.

Quote:

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Originally posted by Andreas Masur
Well...gcc stands for GNU Compiler Collection, which simply acts as a front end for the underlying compilers it contains. The former name was GNU C Compiler, at that time it was only a simple C compiler...

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Yes but what is the default language for gcc? The meaning of gcc is not very relevant; the default language is.

Quote:

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Originally posted by kasracer
Do not pass void to functions in C++.

Sorry, I know that doesn't fix your problem but it is SO annoying when people do that =/

I'm wierd

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Why so ?

Sincerely,

Quote:

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Originally posted by nsh123
Why so ?

Sincerely,

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Because the C++ standard says NOT to. A function requiring no arguements (you don't want to send any to main) does not need to be sent void. That is C, not C++ style.

Quote:

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Originally posted by kasracer
Because the C++ standard says NOT to. A function requiring no arguements (you don't want to send any to main) does not need to be sent void. That is C, not C++ style.

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you are mistaken. void is a perfectly legal C++ function argument - I dare you to show me the exact paragraph in the standard that says different. however, if you DO look at the standard, you'll see something like the example in 8.3.5.1, saying that

int f();
means
int f(void); in C++
and
int f(unknown) in C

to come back to the original thread question, cout is not a part of STL - and to use C++ standard objects you need to link against the implementing library (libstdc++.* in this case). g++ automatically does this for you, while the generic frontend gcc does not and requires -lstdc++

finally, you DO want sometimes arguments to main() - ever heard of:

int main(int argc, char** argv)

Quote:

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Originally posted by KnNeeded
I tried to use the iostream template class in the STL library

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As abc_coder points out, iostreams is not part and has never been part of STL. The iostreams library has existed since the first C++ compilers existed, separate and apart from STL. Go to the SGI web site and look in the STL section -- you will find nothing there about iostreams. Get a book on just STL -- again you will find nothing on iostreams (except maybe an example using cout).

I know it sounds like a small thing to be concerned about, but I have seen programmers waste valuable time looking for information on iostreams, and where do they look? They look in the STL references, thereby not finding anything, wasting their time.

Regards,

Paul McKenzie

Quote:

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Originally posted by abc_coder
you are mistaken. void is a perfectly legal C++ function argument

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So is many other things in C but that doesn't mean you should do it.

Quote:

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Originally posted by abc_coder
I dare you to show me the exact paragraph in the standard that says different. however, if you DO look at the standard, you'll see something like the example in 8.3.5.1, saying that

int f();
means
int f(void); in C++

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You do realize that proves my point, right? It shows that f() means the samething as f(void).

Besides, when I did a search for 8.3.5.1 I didn't find ANYTHING, but in the standard in 8.3.5 it mentions

Quote:

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restricts the use of void as parameter type

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I don't even know why you would top this thread now, it's a bit late.

Quote:

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Originally posted by kasracer
You do realize that proves my point, right? It shows that f() means the samething as f(void).

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let me spell it out then. you said:

Quote:

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Originally posted by kasracer
Do not pass void to functions in C++.
...
Because the C++ standard says NOT to.

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and you were wrong - there's no such interdiction in the C++ standard.

Quote:

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Originally posted by kasracer
Besides, when I did a search for 8.3.5.1 I didn't find ANYTHING, but in the standard in 8.3.5 it mentions restricts the use of void as parameter type

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My bad - the quote I gave was from Appendix C (C1.6 Clause 8: Declarators). However, you seem to have read 8.3.5 incompletely, since it explicitly says (again) that (void) is equivalent to (). The reason is this is an incompatibility with the C standard where () means no parameter specification. I presume you were referring to the following from 8.3.5.2 (your quote is not verbatim):

Quote:

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If the parameter-declaration-clause is empty, the function takes no arguments. The parameter list (void) is equivalent to the empty parameter list. Except for this special case, void shall not be a parameter type (though types derived from void, such as void*, can).

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so yes, it's restricted EXCEPT for this case.

Quote:

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Originally posted by kasracer
I don't even know why you would top this thread now, it's a bit late.

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if you check the thread, nobody had previously corrected the original poster's mistake about confusing iostream objects (in particular cout) with STL objects. second, nobody corrected your assertion about (void) being forbidden. It's only longer to write than (). Some people actually prefer to put it explicitly when they deal with both C and C++ code just to avoid confusions.
Given that the thread was in a 'forum highlights' issue, uncorrected mistakes after such a long time can damaging. Speaking of which, the reccomended use of STLport is overkill. g++ has a complete implementation of STL, no need to download a different one unless there's some obscure implementation incompatibility that one wants to avoid when moving between platforms.

Quote:

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Originally posted by abc_coder
to use C++ standard objects you need to link against the implementing library

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How is that done for VC? I am not aware of doing that for VC. If I need to do it for VC then I don't know how it is done and I don't know how it is possible to not do it.

Back to the OP's question. I have limited experience with Linux, but when I need to use a certain STL implementation I pass the path of the headers to the compiler using (if my memory serves me right) the -I option, like

Code:

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gcc -I path_to_stl file.cpp file.o

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There probably are more option switches in that command, I'm just illustrating.

HTH,

Quote:

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Originally posted by Sam Hobbs
How is that done for VC? I am not aware of doing that for VC. If I need to do it for VC then I don't know how it is done and I don't know how it is possible to not do it.

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But the OP and what abc_coder is talking about has nothing related to VC.
That s just a thought...:)

Regardlessly,
Homestead

Quote:

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Originally posted by Gabriel Fleseriu
Back to the OP's question. I have limited experience with Linux, but when I need to use a certain STL implementation I pass the path of the headers to the compiler using (if my memory serves me right) the -I option, like

Code:

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gcc -I path_to_stl file.cpp file.o

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There probably are more option switches in that command, I'm just illustrating.
HTH,

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the compiler will usually have a list of standard search paths; same goes for the linker. in particular, in Lunix g++ (the c++ compiler) will add to the standard include search path (/usr/include) the path to where its c++ headers are installed (usually /usr/include/c++/x.y.x/ where x.y.z is the g++ version). thus if you're using the compiler's version of the library no header path is required, otherwise (or if using the generic gcc frontend) use the -I switch. same goes for the stdc++ library: g++ links it automatically, while gcc needs an explicit mention.

Quote:

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Originally posted by Sam Hobbs
How is that done for VC? I am not aware of doing that for VC.

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VC does it automatically for you (depending on what type of project you selected). check for instance the project's linker options for the list of libraries that it's linking against.

Quote:

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Originally posted by Homestead
But the OP and what abc_coder is talking about has nothing related to VC.

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It definitely is related to VC. VC implements the standard, and the comment I replied to said "to use C++ standard objects you need to link against the implementing library". That comment said "C++ standard", therefore VC is relevant. I know that this is the non-VC forum, but unless that statement is relevant to all compilers except VC, then VC is an example that applies to the other relevant compilers.

Quote:

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Originally posted by Gabriel Fleseriu
Back to the OP's question. I have limited experience with Linux, but when I need to use a certain STL implementation I pass the path of the headers to the compiler using (if my memory serves me right) the -I option, like

Code:

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gcc -I path_to_stl file.cpp file.o

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There probably are more option switches in that command, I'm just illustrating.

HTH,

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The original question asks about a linker error, implying that there is not a problem compiling, implying tat there is not a problem with the compiler finding the path of the headers.

Quote:

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Originally posted by abc_coder
VC does it automatically for you (depending on what type of project you selected). check for instance the project's linker options for the list of libraries that it's linking against.

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There is nothing linked for the STL by VC. All of the STL is implemented in the headers. Since VC uses the Dinkumware implementation (right?) this would apply to other compilers (the ones that use the Dinkumware implementation) and all users of the Dinkumware implementation (since it can be purchased separately from a compiler).

Quote:

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Originally posted by Sam Hobbs
It definitely is related to VC. VC implements the standard, and the comment I replied to said "to use C++ standard objects you need to link against the implementing library".

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I apologize for the imprecision - that was referring to precompiled objects/classes that need to be linked in (the OP had a linking problem due to cout). As you already said, STL resides usually only in headers (there can be exceptions of custom non-template parts that are compiled in by some implementations).

the point was the OP's (total?! :D ) confusion about what STL is:

Quote:

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I tried to use the iostream template class in the STL library

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peace! :lol:

Is it true that VC uses the Dinkumware implementation ?
How do people know that ? Where can I find a specification to let me know that ?

Thanks

BestRegards,

homestead

It s really hard to get any help ?

Regards,
homestead
:)

Quote:

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Originally posted by Homestead
Is it true that VC uses the Dinkumware implementation ?

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Although this is being off-topic for this thread...yes, VC uses the Dinkumware STL implementation by default...

Quote:

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Originally posted by Andreas Masur
Although this is being off-topic for this thread...yes, VC uses the Dinkumware STL implementation by default...

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I asked so because it is written in Sam's post...I didnt quote his post.
But thanks alot for your answer.

Regards,
homestead