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Date: Wed, 28 Jun 2023 17:04:48 +0200
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To: djgpp AT delorie DOT com
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From: "J.W. Jagersma (jwjagersma AT gmail DOT com) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
Subject: fcntl() fails to pass option flags to fs-ext handler
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Reply-To: djgpp AT delorie DOT com

Hi all,

I was trying to make a non-blocking socket in Watt32 via:

    fcntl(sock, F_SETFL, O_NONBLOCK);

To my surprise, it did nothing.  Replacing fcntl() with fcntlsocket() does set
the flag correctly, but that's not a portable solution.

Looking at the libc code, I see the fsext handler is invoked via:

    int
    fcntl(int fd, int cmd, ...)
    {
    
    /* ...  */
    
      func = __FSEXT_get_function(fd);
      if (func)
      {
        int rv;
        if (__FSEXT_func_wrapper(func, __FSEXT_fcntl, &rv, fd, cmd))
          return rv;
      }
    
    /* ...  */
    
    }

From what I can tell, the flags (in va_list) are never passed through to the
fsext handler.  Has this ever worked?  It seems like a bug to me.