# Table of Contents

- Introduction
- What you'll need to find bugs
- Recommended reading
- Isolating bugs
- X Protocol Errors
- Submitting bug reports
- Submitting patches
- Where to send bug reports and fixes

# Introduction

Bug hunting in LessTif isn't really all that different from bug hunting in 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.

# What you'll need

Let's see:

- a computer (Ta-dah!)
- the X Window System, at release level R5 or above
- a compiler/assembler/linker
- a debugger
- some test code

Of course, if you don't have that, you probably don't need to read this, do you?

# Recommended Reading

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:

- Volume 1: Xlib Programming Manual
- Volume 2: Xlib Reference Manual
- Volume 4: X Toolkit Intrinsics Programming Manual
- Volume 5: X Toolkit Intrinsics Reference Manual
- Volume 6A: Motif Programming Manual
- Volumn 6B: Motif Reference Manual

If you have R6 (Linux, *BSD, others), you'll want:

- Programmer's Supplement for Release 6

From the OSF, you'll want

- OSF/Motif Programmer's Reference (for 1.2)
- OSF/Motif Programmer's Guide (for 1.2)

The style guide is nice, but not required.

# Isolating bugs

Ok, your favorite Motif program is barfing on lesstif, and you're so inclined to help us fix the problem. Problems generally fall into four broad categories:

- Behavior
- Visual
- X Protocol Error
- Core dump

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 -sync

It'll probably spit out a bunch of debug messages (especially if you set the DEBUGSOURCES 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". 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).

# About X Protocol Errors

Sometimes the program will fail with something like:

    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.

# Submitting bug reports

When (not if) you find a problem with Lesstif, we really want to know. Ideally, a patch is what we'd prefer. 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. Try to be complete if you send just a description -- meaning if you send something like:

"Well, I ran an app, and the thingie at the bottom of the wossname didn't look right"

Your are in all likelihood going to be ignored.

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.

If you do send a bug report against a scheduled release, please include the release number.

# Submitting patches

Patches are the preferred form of bug report, as it lessens our efforts to track down where the bugs are. If you do submit a patch, please try to keep a few rules in mind:

- when writing your fix, please try to follow the coding style of the file you are fixing. We are currently debating coding standards, so expect to see one soon.
- try not to submit a fix that creates dead code. Using "#if 0" or commented code is discouraged. We can do that (because, after all, we are the elitist core team;), but you are discouraged from that, because it makes the patches hard to read.
- do not be discouraged if your patch is not accepted verbatim. Often people submit patches that one or more of the core team will recognize as identifying a problem, but the core member will recognize that your fix will break some other piece of functionality. We'll try to tell you, but we're human, so we may forget.
- Remember that relay mailers are free to alter the content of text messages, and often do so. Lines should always be less than 80 characters in length.
- If you are working on OS/2, remember that mailers will usually convert <carriage-return><line-feed> into just <line-feed>. This has in the past caused patches to be rejected by the patch program, and thus by us.
- We prefer patches in the "unified diff" format (with GNU diff, this is "diff -u"). If you have to, you can send a "context diff". Please use one of those two formats.
- If you have a large patch, or a patch that alters a large number of files, please use the "deltas" script included in the distribution to create your patch. This may not be possible if you are working on a somewhat esoteric platform, but do try to follow at least the spirit of the script, in that your patch includes the entire source tree (which enables us to apply it easily, and to quickly identify the altered objects). The "deltas" script includes documentation both on it's usage, and it's purpose.

# Where to send bug reports and fixes

Please send them by E-mail to lesstif@hungry.com, the LessTif mailing list.

Thanks, and remember: all help is appreciated.

Please send comments, questions, ... to the mailing list.

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