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From: Marco Atzeri <marco DOT atzeri AT gmail DOT com>
Subject: X widget question
To: "cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Message-ID: <56EE7412.8080708@gmail.com>
Date: Sun, 20 Mar 2016 10:57:38 +0100
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I have finally identified where ncview was
segfaulting on X86_64

The solution was to reverse the order of destruction
for a chain of widgets

         i=0;
-       while( (w = *(diminfo_row_widget + i++)) != NULL )
-               XtDestroyWidget( w );
+       while( (w = *(diminfo_row_widget + i)) != NULL )
+               i++;
+       while( i>0 ) {
+               i--;
+               XtDestroyWidget( *(diminfo_row_widget + i ));
+       }
  }

that were connected by a vertical constraints:

     *(diminfo_row_widget+ll) = XtVaCreateManagedWidget(
            widget_name,
            boxWidgetClass,
            commandcanvas_widget,
            XtNorientation, XtorientHorizontal,
            XtNfromVert, *(diminfo_row_widget + (ll-1)),
            XtNheight, bb_height,
            XtNwidth,  bb_width,
            NULL);

The segfault was inside Xlib when managing the constraints.

As the segfault did not happened on i686, is it possible
that is a race inside Xlib  ?
I have not found in the X Documentation nothing about
requested order of widget destruction in this case.

Thanks in advance
Marco

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