Question

I am trying to use notify a main gtk thread ( from a separate thread) that some even occurred using pipes. I get the following warning when I am trying to setup pipes. What is a good workaround?

when I can this g_io_channel_win32_new_fd, I see this warning, and thus pipe isn’t created at all 🙁

GLib-WARNING **: giowin32.c:1564: 3 isn’t a C library file descriptor

    int fds[2];
    GIOChannel* gioChannels[2];
    HANDLE rdPipe, wrPipe;
    SECURITY_ATTRIBUTES saAttr;

    saAttr.nLength = sizeof(SECURITY_ATTRIBUTES); 
    saAttr.bInheritHandle = TRUE; 
    saAttr.lpSecurityDescriptor = NULL;
    if (CreatePipe(&rdPipe, &wrPipe, NULL, 1024)) 
    {
       fds[0]  =_open_osfhandle((gssize)rdPipe,  O_RDONLY); 
       fds[1] = _open_osfhandle((long)wrPipe,_O_APPEND);

       gioChannels[0] =g_io_channel_win32_new_fd(fds[0] );
       gioChannels[1] =g_io_channel_win32_new_fd(fds[0] );

       g_io_add_watch( gioChannels[1],(GIOCondition) (G_IO_IN | G_IO_HUP), 
                        (GIOFunc)SomeCallaback,(gpointer)this );

    }

The goal is to notify main application that something occurred in thread thread. In my case, I can’t use gtk in multi-threaded way (calling functions of main thread from spawned one), so I am trying to do it via pipes.

I also saw that it could be a visual studio issue in this thread

Any suggestions?

Answer 1

Like the error says, handles created by CreatePipe are not file descriptors. The Windows programming model does not use file descriptors, so you cannot normally mix and match Windows and non-Windows I/O functions. I suspect if you removed some of the casts in your code, your compiler would pinpoint the problem – C-style (or reinterpret) casrs in C++ code
are almost always a sign you are doing something wrong.