Green Green - 1 month ago 10
C++ Question

undefined reference to '_WSAStartup@8'. How to link libraries with NB?

I use NetBeans, Windows and Cygwin with g++ compiler.

I'm examining Windows Sockets 2. I do everything that is written in MS manual. I have a code (mostly from this manual):

#include <winsock2.h>
#include <ws2tcpip.h>

#include <cstdlib>
#include <iostream>

#pragma comment(lib, "Ws2_32.lib")

int main() {

WSADATA wsaData;

int iResult;

// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
else cout << "Initialization OK.";

return 0;
}


And I have a problem when I try to run the project:

undefined reference to `_WSAStartup@8'


I understand that
Ws2_32.lib
is missing. This is because I do not have Windows SDK installed. But before installing it I want to try out tools that Cygwin offers. It has all the
w32api
header files, I have them in:

C:\cygwin\usr\include\w32api


And it has some
w32api
almost
.lib
files in the directory:

C:\cygwin\lib\w32api


But all these lib files are different, they have
.a
extension and a little bit different name, like:

libws2_32.a // in Cygwin
vs.
ws2_32.lib // in Windows


When I use Cygwin terminal to create an
.exe
file, everything works fine. The commands I input are:

cd C:\\c++\\myProgram // go to the dir
g++ myProgram.cpp -lws2_32 // compile using -l option to link libws2_32.a


And after it I get
a.exe
file. I run it and it works:

./a.exe // Initialization OK.


But as I said I use NetBeans. And if I try to run the project from NB (
[F6]
button) I always have this error undefined reference to '_WSAStartup@8'.

I've tried already everything I could find on NB forums. I've tried to link
libws2_32.a
to my project this way. I go to:

File -> Project Properties -> Linker -> Libraries


And there are three options:

Add Library...
Add Library File...
Add Option...


I've tried them all. I've tried to link both just
Add Library...
and
Add Library File...
. I've also tried to add such an option in the
Add Option...
button:

Add Option... -> Other option -> // and I input here "-lws2_32"


But whatever I do I can't run the project from NB, I get error undefined reference to '_WSAStartup@8'.

So it seems that it is not a problem (error) in the code. It seems that the problem is with NB, with its possibility to link libraries. Or I do wrong steps to attach them to the project.

So my questions are:

1) What do I do wrong? How may I run the project right from NB? I didn't try to install Windows SDK, I want to try with Cygwin tools as it has such kind of tools.

2) What is the difference between Windows
.lib
files and Cygwin
.a
files? Is it better to install Windows SDK and just forget about those
.a
files? Everything I could find so far about them on Cygwin site is this:


The import library is a regular UNIX-like .a library, but it only
contains the tiny bit of information needed to tell the OS how your
program interacts with ("imports") the dll. This information is linked
into your .exe. This is also generated by dlltool.


3) Is it possible to use
#pragma comment(lib, "libws2_32.a")
to link
.a
files? I've tried but didn't get success results.

Answer

1) What do I do wrong? How may I run the project right from NB? I didn't try to install Windows SDK, I want to try with Cygwin tools as it has such kind of tools.

Try this: http://forums.netbeans.org/ptopic44959.html

2) What is the difference between Windows .lib files and Cygwin .a files? Is it better to install Windows SDK and just forget about those .a files?

Both of these files in this particular case are called "import libraries". Import libraries are basically a file containing a list of valid functions, so that when you link your exe, the linker knows that those functions will exist in some particular DLL. So when you link to wsock32.lib or ws2_32.lib, the linker now knows that these functions will exist in wsock32.dll and ws2_32.dll. Thus, it will not complain. Now, the .lib import library format is Microsoft's format. GCC/unix/linux/mingw/cygwin etc. have a different format, and the extension for that format is .a. Now, cygwin/mingw etc. provide a ws2_32.a so that when using cygwin/mingw/gcc, the linker can read the import library in the correct format. cygwin/mingw/gcc will simply not understand the .lib. Microsoft provides the .lib files in their SDK, but I am not sure how this will help in this case. (Though the SDK is definitely useful, because it provides lots of header files and DLLs for other useful things you might need, but the import libraries are useless, because gcc/mingw/cygwin will not understand them; unless you use a converter tool, like the one mentioned in your duplicate question).

3) Is it possible to use #pragma comment(lib, "libws2_32.a") to link .a files? I've tried but didn't get success results.

No, the #pragma linking comments are an MSVC specific (ugly IMO) extension. Use the linker options in the menus.

Comments