Revision as of 23:58, 1 April 2010

Initial version by Dario Andres (2010-03). Corrections by Lydia Pintscher

Disclaimer

All this guide is based on my own experience (approximately 2 years) on the KDE bug tracker.

It may not work for you ;)

General Considerations

• Be polite: when you need to request information or feedback be clear and polite, and you will get more information in less time. 
Often Bugzilla is a place which involves discussions (about implementations, or even about contributors). Try to be concise and polite, respecting the others position while describing your own.

• Don't try to do too many things at the same time; otherwise you will end up with a headache.

If you are not familiar with the Bugzilla (KDE bug tracker system) interface, you may find this guide useful: Quick Introduction to Bugzilla

About getting permissions to work in the bug tracker

Manpower is always needed in a bug tracker, but as any action taken on it may be potentially destructive to other people's work; or it may end up messing things up (and consuming the developers' or other triager's time) the tracker requires special permissions to perform changes in bug reports.

If you want to work in the bug tracker you need to prove that you know what you are doing.

Initially you will ask for support on #kde-bugs (on IRC) and add comments in the bug report (so other people will see and check them, perform the needed actions, and evaluate your work)

Getting Started: Find what to work on (Different Approaches)

You could use different techniques or approaches to triage the reports according to your current mood or the amount of work you want to do for example.

Note: The two following techniques are complementary.

Check all the bug reports of the day

In this technique you check all the bug reports (of all the products) which were filed today (or some days ago).

You can focus on crash, normal or wish reports individually (recommended) or all of them together.

Good:

• You get a complete view of all the reports
• You can easily recognize possible duplicates if the report titles are appropriate
• You can choose any report
• You can quickly clean the bugs that were filed recently (keeping them from rotting)
• You can get quick feedback from the reporter

Not so Good:

• You don't focus on one product
• You may not pay too much attention to every report, as you are triaging different kinds of reports
• You need a lot of attention to handle the different reports (at the ~same~ time)

This technique could be used every week (or every day)

Bugzilla Links (TODO)

• All the bugs (any type) reported today or the last week
• All the crashes reported today or the last week
• All the normal bugs reported today or the last week
• All the feature requests reported today or the last week

Check bug reports of a product over a period of time

Choose a product (application or library). Then choose a period of time like 1 month or 1 or 2 years (or "from the beginning of the current year"). You can also choose which kind of reports you want to handle.

This technique is useful to audit old bugs or perform a deep clean (in case that the bugs weren't triaged on a daily basis previously).

Good:

• You focus only on one product / topic, so you don't need to pay too much attention (pay attention anyways!)

Not so Good:

• The reports of the other application may rot if they aren't checked
• You may not get feedback if the report is too old or the reporter is not accessible anymore

You can also filter out results (and be even more focused) if you select a custom component inside the product (a subsection of the application).

This technique could be used two times a month.

Bugzilla Links (ToDo)

• Template search for all the reports of any status, since 2008: any kind of report, crashes, normal bugs, feature requests
• Template search for all the open reports, since 2008: any kind of report, crashes, normal bugs, feature requests

Workflow of the bug triaging activity

Now that you have a list of bug reports, pick one !

Workflow Graphic (ToDo)

Handling reports: What to do with a bug report

There are several things that must be checked and "fixed" to make an initial bug report an interesting and useful peace of information for the developers to check.

As KDE has too much users, we get a lot of reports about bugs which are already reported (the so named "duplicates"). Before putting any effort in the current report we should check for the main report.

Identifying duplicates

There are a lot of ways of identifying duplicate reports depending of the kind of bug.

General

• Search for duplicates should be done initially against the same product of the bug report you are triaging: 
If you don't find any related issue, you may need to search in a different product.

• You may want to filter out the results by date: you can select a date range since some years (or months ago) to "Now" (today)

(Link ToDo) List of related KDE technologies

For "normal" (non-crash) reports

1. Pick some "keywords" from the current report. This keywords need to explain the inner concept of the bug that was reported (they must represent it).
2. Perform a full search over the same product (read general note), initially on the "general" component.
 Initially, put the keywords in the title, and perform the search (this will only look for the keywords in the title)
3. If your search has results on it, check them all, reading the whole description and trying to identify the situation.
4. If you don't get any results, you need to go back and:

   • Change your keywords (tip: select thesaurus, or similar/related concepts); or
   • Use the keywords in the "Comments" field (so the search will look up in the bug description and comments too)

For "crash" reports

1. Perform the same operation as with normal bug reports
2. Check for reports with duplicate backtraces: 
 (Read the Backtraces section below)

Perform a full search over the same product (read general note), initially on the "general" component, putting the "ClassName::FunctionName" pairs that identify the crash in the Comments field of the form (if you put more than one pair, you need to select the option "contains all of the words/strings")

Processing search results

• If you don't find any similar report then we should assume the new bug reports is "unique" (and valid). See next section


• If you find a similar bug report we have too choices:
  • If you are completely sure it is the same issue, you have to mark the report as duplicate. 

The bug report you initially picked (name it "copy") is going to be marked as duplicate of the original report (name it "main"). If "copy" has additional information that "main" doesn't have, you may want to add it. (Note: some details may look unimportant to you, but they may be important for developers who know about the application workflow and code. Also, adding a big amount of minimal/incomplete information you may end up generating a big and complete testcase)

  • If you aren't completely sure: you need someone else to double check your work. You may want to add a comment in the current report saying "This bug looks related to bug XXXXXX" (XXXXXX being the bug ID of "master"). Then, you should ask in #kde-bugs IRC channel for someone to look at your comment.

C++ Backtraces (identifying crashes duplicates)

Definition

A backtrace is a piece of information that describes what was the application doing when it encountered the error and had to close itself. It is a "function stack" leading to the "crashing point".

In KDE applications, the backtraces are generated by the Crash Handler Dialog ("DrKonqi"). They can also be generated by the general debugger "GDB", but that involves more steps.

The backtrace is read from top to bottom

The first line shows *where* the crash occurred (because of an illegal instruction, invalid pointer, memory problem or other issues)

The other lines show the "way to the first function"

Example

Application: Plasma Workspace (kdeinit4), signal: Bus error
[KCrash Handler]
#5  0x00007fb563bb8f02 in KPixmapCache::Private::mmapFile (this=0x92df60, 
filename=..., info=0x92dfb0, newsize=33656832) at /usr/src/debug/kdelibs-
4.4.1/kdeui/util/kpixmapcache.cpp:491
#6  0x00007fb563be3c34 in KPixmapCache::Private::mmapFiles (this=0x92df60) at 
/usr/src/debug/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:419
#7  0x00007fb563be38e3 in KPixmapCache::Private::init (this=0x92df60) at 
/usr/src/debug/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:1061
#8  0x00007fb563be576d in KPixmapCache::discard (this=0x1203ca0) at /usr/src
/debug/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:1279
#9  0x00007fb563be5e48 in KPixmapCache::deleteCache (name=...) at /usr/src
/debug/kdelibs-4.4.1/kdeui/util/kpixmapcache.cpp:1255
#10 0x00007fb55afdc97d in Plasma::ThemePrivate::discardCache (this=0x7a7d30) 
at /usr/src/debug/kdelibs-4.4.1/plasma/theme.cpp:224
#11 0x00007fb55afe009b in Plasma::ThemePrivate::setThemeName (this=0x7a7d30, 
tempThemeName=<value optimized out>, writeSettings=<value optimized out>)
at /usr/src/debug/kdelibs-4.4.1/plasma/theme.cpp:380
#12 0x00007fb55afe19fb in Plasma::Theme::settingsChanged (this=0x70af20) at 
/usr/src/debug/kdelibs-4.4.1/plasma/theme.cpp:341
#13 0x00007fb55afe2918 in Plasma::ThemePrivate::settingsFileChanged 
(this=0x7a7d30, file=<value optimized out>) at /usr/src/debug/kdelibs-
4.4.1/plasma/theme.cpp:335
...

Description of a backtrace line

#NumberInTheStack MemoryAddress in Namespace::Class:FunctionMember 
(argumentThis=pointerValue, argument1=value, argument2=value, ...) at path/to
/source/code/file.cpp:linenumber

• #NumberInTheStack: is the order number in the function stack. The lesser, the nearer to the crash point. The smaller number may not be zero
• MemoryAddress: we don't put attention to this one.. Ignore
• Namespace: C++ namespace of the function. It may not be available if there are no namespaces. This could be also a class name if "Class" is an embedded one.
• Class: C++ class name of the function
• FunctionMember: C++ function name
• argumentThis=pointerValue : this first argument is often the memory address/pointer of the C++ object (example "this=0x91ec5f8"

other argument use the same form "parameterName=parameterValue"
• (..): arguments supplied to the function. This information may not be available if *debug information* is not present


• path/to/source/code/file.cpp:linenumber the path to the source code file that describes that function, and the line number. The path is the one found at build time. This information may not be useful if debug information is not available (in that case, the name of the library or application binary may be included. Example: /home/kde-devel/kde/lib/libsopranoclient.so.1)

Example:

#13 0xb759d5d7 in Nepomuk::ResourceData::determineUri (this=0x91ec5f8) at 
/home/kde-devel/kde/src/KDE/kdelibs/nepomuk/core/resourcedata.cpp:671

• The function is the number 13 in the stack
• Function's namespace: "Nepomuk"
• Function's class: "ResourceData"
• Function's function: "determineUri"
• The object "Nepomuk::ResourceData" which called to "determineUri" has the pointer "0x91ec5f8"
• The function is described (where it was build) at "/home/kde-devel/kde/src/KDE/kdelibs/nepomuk/core/resourcedata.cpp". It leads to the next function in the stack at the line number 671

Identifying the first (useful) backtrace functions

The first thing you need to do is to locate where it crashed, identifying the "[KCrash Handler]" mark (only in backtraces fetched using DrKonqi)

If the application only had one thread, then it is at the top of the unique thread; otherwise you may need to look at all the thread (the KCrash mark may not be always in the Thread number 1)

Once that you located the "crashing thread start", pickup the first two or three "ClassName::Functions" pairs from top to bottom (some functions should be ignored, read below)

This pairs will be used as "keywords" for the duplicate search

f the first backtrace functions aren't available (they are not there, or there are "??" )then we can't proceed without requiring more information (a more complete backtrace) [Ask for more information Todo Link]

Avoiding useless function calls

Some functions or calls are common to a lot of applications using the same core libraries (like the Qt library, glib, glibc, or many others). This kind of functions should not be used for search as they are not representative of the crash itself and it may return lots of results.

Classes and functions to ignore in backtrace:

• Kernel/GLibC functions (__kernel_vsyscall, raise, abort)
• Functions from core/base libraries (libraries with filenames like libpthread.so.0, libc.so, libstdc++.so, libglib-2.0.so; or functions starting with "*__GI_"). You may also need to ignore calls to graphics drivers (like nvidia or libGL)
• Qt containers classes (QMap, QList, QLinkedList, QVector, QStack, QQueue, QSet, QMap, QMultiMap, QHash, QMultiHash)
• Qt deep core classes (QApplication, QCoreApplication, QBasicAtomicInt, QBasicAtomicPointer, QAtomicInt, QAtomicPointer, QMetaObject, QPointer, QWeakPointer, QSharedPointer, QScopedPointer, QMetaCallEvent)
• Qt misc functions (qt_message_output, qt_message, qGetPtrHelper, (starting with) qt_meta_)

Special cases (Advanced)

There are special crashes related to the X11 graphics server. To identify this crashes you can search for the "XIOError" function name (often on Thread 1). The "[KCrash handler]" mark appears in a secondary thread.

The important things to identify those crashes is recognizing the functions *below* the XIOError call (this is, which functions caused the X11 error).

In most of this crashes the functions below "[KCrash handler]" are not important (but they could still be useful to search for duplicates).

Trying to reproduce the bugs

Getting bug triaging support

BugWeeks

FAQ

More Information