On Wednesday, April 29, 2009 at 21:58:03 (+0100) Andrew Ross writes:
> Further testing has shown that I can get rid of the segmentation fault by
> removing the call to XInitThreads in the OpenXwin function in xwin.c.
> According to the Xlib documentation:
>
> "The XInitThreads() function initializes Xlib support for concurrent
> threads. This function must be the first Xlib function a multi-threaded
> program calls, and it must complete before any other Xlib call is made.
> This function returns a nonzero status if initialization was successful;
> otherwise, it returns zero. On systems that do not support threads, this
> function always returns zero.
>
> It is only necessary to call this function if multiple threads might use
> Xlib concurrently. If all calls to Xlib functions are protected by some
> other access mechanism (for example, a mutual exclusion lock in a toolkit
> or through explicit client programming), Xlib thread initialization is
> not required. It is recommended that single-threaded programs not call
> this function."
> ..
> In particular, with the tk support there may be other Xlib calls
> elsewhere which are not protected. It is also probable that
> XInitThreads is not actually the first Xlib call in this case.
It is not. In plframe.c the window is created by:
new = Tk_CreateWindowFromPath(interp, Tk_MainWindow(interp),
argv[1], (char *) NULL);
which ultimately terminates in a call to XCreateWindow(). From the Tk
generic/tkWindow.c --
* tkWindow.c --
*
* This file provides basic window-manipulation procedures,
* which are equivalent to procedures in Xlib (and even
* invoke them) but also maintain the local Tk_Window
* structure.
The partial initialization of the xwin driver the plframe widget does after
that may not require the window to actually already exist -- I don't see any
explicit dependence, although it's been too long for me to remember if I ever
tried doing the two ops in reverse order. You might want to give this a try.
I.e. move the code
/* Partially initialize X driver. */
pllib_init();
plsdev("xwin");
pllib_devinit();
plP_esc(PLESC_DEVINIT, NULL);
above the call to Tk_CreateWindowFromPath().
--
Maurice LeBrun
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