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==C++ Backtraces (identifying crashes duplicates)==
==C++ Backtraces (identifying crashes duplicates)==
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=Trying to reproduce the bugs=
=Trying to reproduce the bugs=
Revision as of 22:53, 1 April 2010
Initial version by Dario Andres (2010-03). Corrections by Lydia Pintscher
All this guide is based on my own experience (approximately 2 years) on the KDE bug tracker.
It may not work for you ;)
- 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)
|adding comments in the bug report is allowed for every user|
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.
- 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).
- 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.
|if at any point you don't really know how to continue, because you don't understand the issue properly, always ask to the developers or related contributors|
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.
There are a lot of ways of identifying duplicate reports depending of the kind of bug.
- 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.
|due to the heavy usage of libraries in the KDE software, a bug reported for an application may be being tracked at a library product (example, a bug in Plasma Desktop may be a bug in kdelibs, and therefore being tracked in the "kdelibs" 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
- 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).
- 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)
- If your search has results on it, check them all, reading the whole description and trying to identify the situation.
- 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)
|when using more than one word in the "Comments" field you need to select the option "contains all of the words/strings"|
|it is sometimes difficult to choose the proper ones, as the way of describing a scene varies from person to person (but we have time)|
For "crash" reports
- Perform the same operation as with normal bug reports
- 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.
|you may found related reports that are already marked as duplicate of a third report. Always try to use this third report as the "main" one. However, in some cases, the "main" reports refers to a root issue, and some of its duplicates may refer to sub-issues. In those cases try to check which refers to the issue you are looking at.|
C++ Backtraces (identifying crashes duplicates)
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"
Application: Plasma Workspace (kdeinit4), signal: Bus error
#5 0x00007fb563bb8f02 in KPixmapCache::Private::mmapFile (this=0x92df60,
filename=..., info=0x92dfb0, newsize=33656832) at /usr/src/debug/kdelibs-
#6 0x00007fb563be3c34 in KPixmapCache::Private::mmapFiles (this=0x92df60) at
#7 0x00007fb563be38e3 in KPixmapCache::Private::init (this=0x92df60) at
#8 0x00007fb563be576d in KPixmapCache::discard (this=0x1203ca0) at /usr/src
#9 0x00007fb563be5e48 in KPixmapCache::deleteCache (name=...) at /usr/src
#10 0x00007fb55afdc97d in Plasma::ThemePrivate::discardCache (this=0x7a7d30)
#11 0x00007fb55afe009b in Plasma::ThemePrivate::setThemeName (this=0x7a7d30,
tempThemeName=<value optimized out>, writeSettings=<value optimized out>)
#12 0x00007fb55afe19fb in Plasma::Theme::settingsChanged (this=0x70af20) at
#13 0x00007fb55afe2918 in Plasma::ThemePrivate::settingsFileChanged
(this=0x7a7d30, file=<value optimized out>) at /usr/src/debug/kdelibs-
Trying to reproduce the bugs
Getting bug triaging support