Guidelines and HOWTOs/Code Checking
Code Checking
There are a lot of ways to find bugs in KDE code. Increasingly, KDE developers have started to use automated tools. You can use some of those tools to improve your own code.
The KDE 'Krazy' Checker
KDE developers have a simple set of tests that are collectively known as "Krazy". These tests were originally developed to be run as part of a larger set of tests on a machine known as http://www.englishbreakfastnetwork.org, or EBN for short. You can see the results of running the various tests on EBN (at http://www.englishbreakfastnetwork.org/krazy/).
You can also run the tests yourself. To do this, you need to obtain a copy of the code from trunk/quality/krazy2 and install them. You can then test either a single file (using the krazy application) or a whole tree, including subdirectories (using the krazyall application).
How Krazy works
The Krazy tests are essentially a form of static analysis - they check the source code, but not how it runs.
Krazy exists as a framework comprising a number of different test runners, and a set of plugins. The test runners are called krazy, krazyall, and krazyebn. The test runners just call one or more plugins on the appropriate code, and format the results for display.
At this stage, most of the test runners are written in perl, however one is written in C++ (using Qt) and it is quite possible to add your own tests, or to modify a test - all sources are provided.
Installing Krazy
Krazy needs to be installed before use. Krazy has two different ways to be installed - you can either modify the krazy2/install.sh script and run it, or follow the instructions in the krazy2/INSTALL.txt file. I recommend the second.
You may need to install additional perl modules like XML::LibXML, here is how:
linux-pudb:~/krazy2 # ./install.sh
MakeMaker FATAL: prerequisites not found.
Tie::IxHash not installed
XML::LibXML not installed
Please install these modules first and rerun 'perl Makefile.PL'. linux-pudb:~/krazy2 # perl -mCPAN -e CPAN::shell
You may have to answer 25 useless questions here. In this case, just press ENTER 25 times. Then you go on like this:
cpan[1]> install XML::LibXML
Note
Using Krazy
Krazy comes with a particularly good man page, which gives you the various options and a usage example. The file is generated on installation. This is definitely recommended reading!
As noted above, there are three test runners - krazy, krazyebn and krazyall. If you are trying to check a single file, then krazy is the right tool. If you are trying to check a source tree (say, an application or a whole subversion module), then krazyall is more useful. krazyall doesn't have a man page, but you can get a list of the options with krazyall --help. You can also use krazy to get information on the various plugins, which can help you understand more about krazyall.
krazyebn is the tool that runs over the KDE codebase on the EBN and should not be run locally. However, please see Controlling Krazy on the EBN below to learn how you can control which plugins are run, and what files are processed by the krazyebn program on the EBN machine.
Remember that Krazy doesn't change your code - it only examines it. So you can safely experiment with running Krazy checks until you are confident that you understand what is happening.
Equally, that means that Krazy doesn't fix problems - it only tries to report them. Understanding what is being reported, and how to fix it, is up to you. You should also remember the KDE commit policy about not committing code that you don't understand. So fixing a spelling error in a comment is pretty safe, but blindly changing code to stop explicit constructor warnings from Krazy is not a good idea.
In-Code directives
The Krazy plugins support the following list of in-code directives:
- //krazy:skip - no Krazy tests will run on this file.
- //krazy:excludeall=<name1[,name2,...,nameN]> - the Krazy tests name1, etc will not be run on this file.
- //krazy:exclude=<name1[,name2,...,nameN]> - the Krazy tests name1, etc. will not be run on the line where this directive is found (see the next section below for more information).
Note that these directives must be C++ style comments that can be put anywhere in the file desired (except embedded within C-style comments).
Suppressing false-positives
The Krazy tests are designed to minimise false positives (that is, alerts that do not represent real problems). However because most of the tests are conducted on a single line, there are some tests that might produce such a false positive. For example, code that does something like:
QString mystring;
mystring += "/";
will be flagged by the doublequote_chars checker, because it is more efficient to add a single char, as shown below:
QString mystring;
// note that we are using single quotes
// this is a char, not a char array
mystring += '/';
That same checker will produce a false positive for code that looks like:
std::string mystring;
mystring += "/";
You can suppress these false positives using a special comment format. To exclude a particular plugin from being run on a line of code, simply add a C++ comment containing the string "krazy:exclude=<plugin_name>". The plugins currently available can be found in the repository.
Specifically, for this plugin use "krazy:exclude=doublequote_chars".
For example:
lenstr = "0" + lenstr;
becomes
lenstr = "0" + lenstr; // krazy:exclude=doublequote_chars
Note
Controlling Krazy on the EBN
This section describes how to use .krazy files to control the Krazy runs on the EBN. The .krazy files are used to tell Krazy to skip over specific sub-directories, or files; or to disable certain plugins within those modules and sub-directories.
To ignore a sub-directory within a module, say kdepim/kmail, use the IGNORESUBS directory within the kdepim/.krazy file, like so:
IGNORESUBS kmail
Or you can ignore a set of directories by specifying a comma-separated list:
IGNORESUBS kmail,kontact,knode
To ignore files or directories within a module/subdir, specify a regular expression that matches the files to skip together with the SKIP directive. For example, to skip the directories kdepimlibs/kcal/libical, kdepimlibs/kcal/versit, and the kdepimlibs/kcal/fred.c file, use this directive within the kdepim/kcal/.krazy file:
SKIP /libical/\|/versit/\|fred\.c
Use the EXCLUDE directive to disable a list of plugins for all files within a module/subdir:
EXCLUDE doublequote_chars,qclasses
To override the EXCLUDE directive set from a .krazy file up in the directory hierarchy, use the CHECK command. For example, the component level .krazy file may EXCLUDE the copyright and license plugins, but those plugins can be re-enabled in a module/subdir with the CHECK directive like so:
CHECK copyright,license
Note
Compiler Warnings
In addition to the various Krazy tools, you can also get valuable assistance from the warnings that the compiler emits, especially if you enable additional warnings (per the documentation for your compiler), and also if you test with more than one compiler (e.g. if you can test on Linux with both GCC and the Intel compiler; or on Linux with GCC and also on Windows with the Microsoft compiler).