Problem with __gnu_cxx::stdio_filebuf and sockets

[Jochen Klenner]

Hi list,

I have trouble using g++'s stdio_filebuf extension with sockets.
I'm using gcc 3.4.1 on a Linux system.
Writing to a stdio_filebuf that is connected to a socket always fails,
leaving the stream in a bad state. See the following program for 
illustration:

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

#include <string>
#include <iostream>
#include <ext/stdio_filebuf.h>

int main() {
   int sockfd = socket(AF_INET, SOCK_STREAM, 0);
   sockaddr_in address;
   address.sin_family = AF_INET;
   address.sin_addr.s_addr = inet_addr("127.0.0.1");
   address.sin_port = htons(119);
   int result;
   result = connect(sockfd, (sockaddr*)(&address), sizeof(address));
   if (result != 0) {
     std::cerr << "connect failed " << std::endl;
     exit(1);
   }

   __gnu_cxx::stdio_filebuf<char> sockBuf
     (sockfd, std::ios_base::in | std::ios_base::out);
   std::iostream sock(&sockBuf);
   std::string in;
   std::getline(sock, in);                   // succeeds
   std::cout << in << std::endl;
   if (!sock.good()) {
     std::cerr << "socket is not good\n";
   }
   sock << "help\n";                         // fails
   if (sock.bad()) {
     std::cerr << "write failed badly\n";
   }

   in.clear();
   sock.clear();
   std::getline(sock, in);                   // hangs
   std::cerr << "have read\n";
}

This program connects to a local newsserver, that gives an informative 
message first, and outputs more text after receiving the "help" message.
While the first getline works, the write does not, and "write failed 
badly" is output. Then the second getline hangs forever.

When I do the same thing using the low-level read and write functions 
instead of stdio_filebuf it works flawlessly.

Any clue about this issue is appreciated.

Best regards

Jochen