Conference bulova::decw_jan-89_to_nov-90

3626.0. "core dump associate with up/down stepping arrows" by MARX::CHOY () Fri Nov 09 1990 18:10

My program gets core dump when it displays messages to a DECwindow, and
at the same time I keep clicking on the up/down stepping arrow of the vertical 
scroll bar.

The program is a background process, it listens to incoming messages through
a well known UDP port. When a message is received, The program writes it to a
database table, and then displays it to a small simple-text widget. The
widget is contained in an attached-dialog-box which has a horizontal and a
vertical scroll bars. There is no call back routine to handle the scroll
bar events.

If there are messages coming, and I keep clicking on the up or down
stepping arrow, the program always core dump at DwtTextSetTopPosition of
the nmsx_display routine. nmsx_display is used to display message to a
simple-text widget.

dbx Debugging information, nmsx_display routine, and part of the uil are
listed below for your reference. 
 
Would appreciate any information.


Debugging information for my program :-

Child died at pc 0x47d830 of signal : Bus error

[using memory image in core]
(dbx) >  0 XtRemoveTimeOut(0x7fffb534, 0x7fffb340, 0x100747ec, 0x10021e20,
 0x4c4950) ["NextEvent.c":393, 0x47d82c]
   1 Scroll.ScrollCallback(0xd, 0x18f, 0x0, 0x0, 0x0) ["Scroll.c":1036,
     0x4c1d30]
   2 Scroll.SetValues(0x7fffb340, 0x7fffb340, 0x100747ec, 0x10021e20, 0x4)
     ["Scroll.c":2584, 0x4c494c]
   3 CallSetValues(0x7fffb534, 0x7fffb340, 0x100747ec, 0x10021e20, 0x4)
     ["Resources.c":860, 0x481530]
   4 XtSetValues(0x10021e20, 0x4, 0x1a, 0x1, 0x1) ["Resources.c":978, 0x481948]
   5 TextOutput.CheckForNewSize(0x7fffffff, 0x0, 0x48118c, 0x15, 0x482164)
     ["TextOutput.c":463, 0x4e58e0]
   6 TextOutput.MeasureLine(0x1005dc1c, 0x1f9, 0x1007af54, 0x1007af50,
     0x4813c0) ["TextOutput.c":530, 0x4e5c2c]
   7 RefigureLines(0x484554, 0x7fffb900, 0x2, 0x2, 0xa) ["Text.c":720,
     0x486ba8]
   8 Text.Redisplay(0x405208, 0x1005e7d8, 0x20e, 0x10051ec0, 0x4052e4)
     ["Text.c":844, 0x4871b8]
   9 DwtTextSetTopPosition(0x7fffb900, 0x1f8, 0x1003b1f0, 0xffffffff, 0x1a)
     ["Text.c":1408, 0x488a28]
  10 nmsx_display.nmsx_display(0x7fffba10, 0xffffffff, 0x1, 0x7fffbad4, 0x0)
     ["nmsx_display.c":153, 0x4052e0]
  11 display_alm_msg(display_type = 1, widget = 2, alm_timestamp = 0x10080dc8
     = " 9-Nov-1990 16:45:46", alm_object = 0x7fffbad4 = "choy", alm_type =
     0x7fffbb1c = "send_alm_msg6", alm_msg = 0x7fffbb3d = "test alarm message
     5.") ["almd_window.c":893, 0x4030d8]
  12 get_msg() ["almd_main.c":306, 0x400690]
  13 IeCallProc(0x0, 0x0, 0x600016, 0x1005dc1c, 0x10061cf4)
     ["NextEvent.c":327, 0x47d640]
  14 DoOtherSources(0x0, 0x4, 0x100747ec, 0x1005dc1c, 0x47f120)
     ["NextEvent.c":667, 0x47de60]
  15 XtAppNextEvent(0x7fffbc98, 0x10005750, 0x47f15c, 0x4, 0x60e)
     ["NextEvent.c":780, 0x47e10c]
  16 XtAppMainLoop(0x1, 0x1000, 0x0, 0x1, 0x400524) ["Event.c":1105, 0x47c78c]
  17 XtMainLoop(0x1, 0x400544, 0x0, 0x0, 0x0) ["Event.c":1096, 0x47c760]
  18 almd_main.main(argc = 1, argv = 0x7fffbd5c) ["almd_main.c":210, 0x400520]


nmsx_display routine :-

/**************************************************************************
 * routine: nmsx_display()
 *
 * description:
 *   this routine displays to the simple text widget passed to the routine.
 *   This routine handles scrolling a little differently than is usual
 *   for the simple-text widget
 *
 * arguments:
 *   widget    -  display text on this widget
 *   str       -  string to be displayed
 *   log_fd    -  file descriptor to write the message to if 
 *                logging is enabled.  log_fd = NMSX_NOLOG  -->  no logging.
 *   nlflag    -  Should a newline be placed after the string befor
 *                displaying?
 *                1 = TRUE  ->  add a newline to the string argument
 *                0 = FALSE ->  do NOT add a newline to the string argument
 **************************************************************************/

#include <X11/DECwDwtApplProg.h>      /* DECwindows toolkit */
#include <nms.h>
#define MAX_WIDGETS   100
extern Widget widgets[MAX_WIDGETS];
extern DRMHierarchy s_DRMHierarchy;
extern Widget toplevel_widget;

nmsx_display(widget, str, log_fd, nlflag)

Widget widget;
char *str;
int  log_fd;
int nlflag;

{
  Arg  wargs[30];
  int  argi;
  static char newtext[LEN_DISPLAY_STRING];
  char *current_contents;
  int  textlen, nlines;
  long int toppos, current_toppos;
  Dimension rows;

  /*
   * We need to do an append, so get a pointer to the current
   * contents of the text widget. 
   */
  current_contents = DwtSTextGetString(widget);
  textlen = strlen(current_contents);
  XtFree(current_contents);
  
  /* 
   * If there is already text in the widget, add a newline to
   * the text we are going to insert. 
   */
  if (textlen > 0 && nlflag) {
    strcpy (newtext, "\n");
    strcat (newtext, str);
  } else {
    strcpy (newtext, str);
  }
  
  /*
   * Insert the new text, specifying the insertion position as
   * the last existing character.
   */
  DwtSTextReplace (widget, textlen, textlen, newtext);
  
  /*
   * The simple text doesn't usually scroll unless the user manipulates
   * the scroll bar. Hence once the window is full, you don't see
   * new lines that are appended to the end of the text. We jump through
   * some hoops here in order to determine which character position of
   * the text should be the one displayed as the first in the window. The
   * idea is to choose that byte such that the last line is visible at the
   * bottom of the window.
   */
  
  /*
   * Get some of the current window characteristics. We need to know
   * the number of lines (rows) that can be displayed and the current
   * offset of the first displayed character. The number of rows can be
   * set in the UIL file, and can be changed by resizing, so we don't 
   * want to hardcode it here. 
   */
  argi = 0;
  XtSetArg (wargs[argi], DwtNrows, &rows);argi++;
  XtSetArg (wargs[argi], DwtNtopPosition, &current_toppos);argi++;
  XtGetValues (widget, wargs, argi);
  
  /* 
   * There is a limit (set in the UIL file as max_length) to the amount
   * of text the window will hold (how far you can scroll back). After
   * that limit is reached, appending new text causes some to be
   * deleted from the top of the text. So we can't assume that the text
   * in the window is its previous contents plus what we inserted
   * above. So get a pointer to the current text in the window.
   */
  current_contents = DwtSTextGetString (widget);
  toppos = strlen (current_contents);
  
  /*
   * Starting from the end of the text, count newline characters
   * until we have enough to fill the window. Then so a little
   * adjusting we we point at the right character to be at the
   * top of the window.
   */
  nlines = 0;
  while (toppos >= 0 && nlines < rows) {
    if (current_contents[toppos--] == '\n') nlines++;
  }
  XtFree (current_contents);
  if (toppos >= 0) {
    toppos += 2;
  } else {
    toppos = 0;
  }
  
  /*
   * If the character we want at the top of the window is different
   * from what it is now, change it. When this program was written
   * trying to do this by setting DwtNtopPosition with XtSetValues
   * caused the text widget to shiver like a bowl of jelly. The
   * procedure call used below works, though. 
   */
  if (current_toppos != toppos) {
    DwtTextSetTopPosition (widget, toppos);
  }

  /* If the logging file descriptor is valid, i.e. >= 0, then
   * write the message to the output file as well as to the 
   * specified widget.
   */
  if (log_fd >= 0)   
    write(log_fd, newtext, strlen(newtext));
}


The simple-text widget is defined as follow :-

! define main window
object
    S_MAIN_WINDOW: main_window {
	arguments {
	};
	controls {
	  menu_bar    s_menu_bar;
	  attached_dialog_box dialog;
	};
    };

! define the main control box widget
object
    dialog: attached_dialog_box {
	arguments {
	  units = DwtPixelUnits;
	};
	controls {
	  simple_text main_display_box;
	};
	callbacks {
	  create = procedure widget_created_proc(control_box_widget);
	};
    };

! define the main window text display area.
object
    main_display_box : simple_text {
        arguments {
	  adb_top_attachment = DwtAttachAdb;
	  adb_left_attachment = DwtAttachAdb;
	  adb_right_attachment = DwtAttachAdb;
          adb_bottom_attachment = DwtAttachAdb;
	  auto_show_insertion_point = true;
	  editable = false;
	  insertion_point_visible = false;
	  max_length = 8192;
	  scroll_horizontal = true;
	  scroll_vertical = true;
	  font_argument = k_default_font;
        };
	callbacks {
	  create = procedure widget_created_proc(main_display_widget);
        };
    };