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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.

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2 に答える 2

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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.

于 2012-09-10T13:39:00.147 に答える
0

eclipse, Cygwin

propeties -> C/C++ Build -> Settings -> Cygwin C Linker

Command line pattern

add to -lws2_32

ex)${COMMAND} ${FLAGS} ${OUTPUT_FLAG} ${OUTPUT_PREFIX}${OUTPUT} ${INPUTS} -lws2_32

于 2016-10-21T07:21:34.387 に答える