Bug hunting in LessTif isn't really all that different from bug hunting in arbitrary X application code, with a few notable exceptions.
We encourage users to help us make LessTif a better product by doing some preliminary ground-work for the developers when you find a bug in the library. Of course, what we really want is a patch that fixes the bug, but we'll settle for some help.
Of course, if you don't have that, you probably don't need to read this, do you?
The following list of books are nice to have, especially the Intrinsics and the Motif books, but you can probably get away without them if you have a full set of man pages.
One thing, though: if you want to understand what widget methods do, and how a widget works, they are an absolute necessity.
The O'Reilly books "The Definitive Guide to the X Window System". Of these, you'll want:
Further details on debugging X11 apps can be found at these writings:
Of these, the first two are more trivial, and (as of now, anyway) are allocated somewhat lower priority, while we work on implementing *missing* behaviors. X Errors and core dumps have a higher priority.
One thing to keep in mind is that the location that the problem occurs in
not necessarily the same as the location that caused the problem; this is
due to the (normally) asynchronous nature of X applications. When your
application has a problem, the first thing to do is run the application
synchronously, to see if the location of the error changes (you'll be
surprised how often it will). Here's how to do it with gdb:
root@zeek:/var/root/lesstif/testXm/filesb# gdb ./test1 GDB is free software and you are welcome to distribute copies of it under certain conditions; type "show copying" to see the conditions. There is absolutely no warranty for GDB; type "show warranty" for details. GDB 4.14 (i586-unknown-linux), Copyright 1995 Free Software Foundation, Inc... (no debugging symbols found)... (gdb) run -sync Starting program: /var/root/lesstif/testXm/filesb/./test1 -syncIt'll probably spit out a bunch of debug messages (especially if you set the DEBUG_SOURCES environment variable). Note that the commands passed to the run command are actually command line arguments to the program.
On some systems, you may find that you can't set breakpoints at the start
if you use shared libraries. That's because the symbols won't be resolved
until a process image exists. To work around this, set a breakpoint at
main(), and run. Once the breakpoint at main is reached,
you'll find that you can set the other breakpoints.
Once you've had your program dump core, just say "where".
This also works if your program just crashed when not running
within a debugger but it created a core dump. Then just
start
gdb program core
and type "where".
Again from gdb:
Program received signal SIGSEGV, Segmentation fault.
0x40076918 in __XmStringGetNextComponent (context=0x8081de0) at XmString.c:68
68 if (context->current_segment < context->string->number_of_segments)
(gdb) where
#0 0x40076918 in __XmStringGetNextComponent (context=0x8081de0)
at XmString.c:68
#1 0x40077ea7 in XmStringGetLtoR (string=0x30,
tag=0x804dc68 "FONTLIST_DEFAULT_TAG_STRING", text=0xbffffa00)
at XmString.c:869
#2 0x8049793 in cb (w=0x8062c00, a=0x0, b=0xbffffa64) at test1.c:32
#3 0x400aa718 in XtCallCallbackList ()
#4 0x4005e7f0 in _XmSbButton (w=0x806cb00, client=0x0, call=0xbffffac0)
at SelectionBox.c:467
#5 0x400aa743 in XtCallCallbackList ()
#6 0x4004e5a0 in Activate (w=0x806cb00, event=0xbffffce4, params=0x0,
num_params=0x0) at PushBG.c:1014
#7 0x4004f10b in input_dispatch (gadget=0x806cb00, event=0xbffffce4,
event_mask=64) at PushBG.c:1360
#8 0x40035ad6 in _XmDispatchGadgetInput (w=0x806cb00, event=0xbffffce4,
mask=64) at GadgetUtil.c:205
#9 0x40045492 in _XmGadgetActivate (w=0x8062c00, event=0xbffffce4,
params=0x0, num_params=0x8059668) at Manager.c:795
#10 0x400d2ceb in HandleActions ()
#11 0x400d35ae in HandleComplexState ()
#12 0x400d365b in _XtTranslateEvent ()
#13 0x400b412f in XtDispatchEventToWidget ()
#14 0x400b4aa9 in _XtDefaultDispatcher ()
---Type <return> to continue, or q <return> to quit---
#15 0x400b4ce3 in XtDispatchEvent ()
#16 0x400b4fd9 in XtAppMainLoop ()
#17 0x80498f1 in main (argc=1, argv=0xbffffd78) at test1.c:69
#18 0x80495a4 in ___crt_dummy__ ()
Note the line numbers. Please do NOT send a trace without having compiled
with debug (the -g option).
X Error: Bad Drawable (other stuff)or something similar. This is a problem with something that got sent to the X server.
This isn't hard to track down if you've run in synchronous mode. Just set a breakpoint at the exit() function, run with the -sync option, and you'll get a trace from the point where the error occurred, plus some other information. These are crucial to proper LessTif functionality -- these must be stamped out.
On the application side specify which program version (including a reference where to get it if it's a "free" application) and how to reproduce the bug. Sometimes one will ran into non-reproducible ones. You should also report them, but due to their somewhat obscure nature they're hard to track down perhaps. Further we need details about the version of LessTif you have installed. These include:
uname -a gives
helpful information.
Ideally, a patch is what we would prefer to receive. Failing that, we need sample code, and a stack trace of the problem (even if it was an X Error). If it was a behavioral or visual problem, just a description will do, although some code that exhibits the behavior would be nice.
We also need the version number of the file that had the problem. If you prefer, and you are using lesstif-current, you can tell us the date you noticed the problem. Please do not tell us the problem two months after you saw it, the code base changes too rapidly for us to be able to make anything meaningful out of a bug report that old.
Some more things to consider:
We have a working bugs database at SourceForge.net !
You may add bugs by using
http://sourceforge.net/tracker/?atid=108596&group_id=8596.
Patches can be sent to our mailinglist if they are quite small. If they are big you should ask first where to send them. Patches of any size are also accepted (probably the best method) on our Patch Manager at http://sourceforge.net/tracker/?atid=308596&group_id=8596&func=browse.
Thanks, and remember:
All help is appreciated!
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