WARNING: master is the development branch. Please use the v1.6 branch.
clazy is a compiler plugin which allows clang to understand Qt semantics. You get more than 50 Qt related compiler warnings, ranging from unneeded memory allocations to misusage of API, including fix-its for automatic refactoring.
- Source Code
- Pre-built binaries
- Build Instructions
- Setting up your project to build with clazy
- List of checks
- Selecting which checks to enable
- clazy-standalone and JSON database support
- Enabling Fixits
- Troubleshooting
- Qt4 compatibility mode
- Reducing warning noise
- Reporting bugs and wishes
- Authors
- Contributing patches
You can get clazy from:
- https://github.com/KDE/clazy
- [email protected]:clazy
- git://anongit.kde.org/clazy
Pre-built binaries are produced by KDAB, you can get them from https://downloads.kdab.com/clazy/. Currently MSVC2015, MSVC2017 (based on clang-7.0) and Linux AppImage packages (based on clang-8.0) are provided.
- OpenSUSE tumbleweed:
zypper install cmake git-core llvm llvm-devel llvm-clang llvm-clang-devel - Ubuntu:
apt install g++ cmake clang llvm-dev git-core libclang-dev - Archlinux:
pacman -S make llvm clang python2 cmake git gcc - Fedora: be sure to remove the llvm-static package and only install the one with dynamic libraries
- Other distros: Check llvm/clang build docs.
clang and LLVM >= 5.0 are required.
If your distro provides clang then you can skip this step.
$ git clone https://github.com/llvm-mirror/llvm.git <some_directory>
$ cd <some_directory>/tools/ && git clone https://github.com/llvm-mirror/clang.git
$ cd <some_directory>/projects && git clone https://github.com/llvm-mirror/compiler-rt.git
$ mkdir <some_directory>/build && cd <some_directory>/build
$ cmake -DCMAKE_INSTALL_PREFIX=<prefix> -DLLVM_TARGETS_TO_BUILD=X86 -DCMAKE_BUILD_TYPE=Release ..
$ make -jX && make install
$ cd clazy/
$ cmake -DCMAKE_INSTALL_PREFIX=<prefix> -DCMAKE_BUILD_TYPE=Release
$ make && make install
See troubleshooting section if you have problems.
These instructions assume your terminal is suitable for development. jom and nmake (or ninja), git, cmake, and cl (msvc2015 or later) should be in your PATH.
clang and LLVM >= 5.0 are required.
Be sure to pass -DLLVM_EXPORT_SYMBOLS_FOR_PLUGINS=ON to CMake when building LLVM, otherwise clazy won't work.
> git clone https://github.com/llvm-mirror/llvm.git <some_directory>
> cd <some_directory>\tools\ && git clone https://github.com/llvm-mirror/clang.git
> git checkout release_90
> cd clang
> git checkout release_90
> mkdir <some_directory>\build && cd <some_directory>\build
> cmake -DCMAKE_INSTALL_PREFIX=c:\my_install_folder\llvm\ -DLLVM_TARGETS_TO_BUILD="X86" -DLLVM_EXPORT_SYMBOLS_FOR_PLUGINS=ON -DCMAKE_BUILD_TYPE=Release -G "NMake Makefiles JOM" ..
> jom
> nmake install
> Add c:\my_install_folder\llvm\bin\ to PATH
Be sure to point CLANG_LIBRARY_IMPORT to clang.lib. It's probably inside your LLVM build dir since it doesn't get installed.
> cd clazy\
> cmake -DCMAKE_INSTALL_PREFIX=c:\my_install_folder\llvm\ -DCLANG_LIBRARY_IMPORT=C:\path\to\llvm-build\lib\clang.lib -DCMAKE_BUILD_TYPE=Release -G "NMake Makefiles JOM"
> jom && nmake install
$ sudo port install clang-3.9 llvm-3.9
$ sudo ln -sf /opt/local/bin/llvm-config-mp-3.9 /opt/local/bin/llvm-config
$ sudo port select --set clang mp-clang-3.9
$ export CXX=clang++
$ cmake
$ make
$ make install
The recommended way is to build clazy yourself, but alternatively you can try user recipes, such as:
$ brew install kde-mac/kde/clazy
for stable branch, or for master:
$ brew install kde-mac/kde/clazy --HEAD
As these are not verified or tested by the clazy developers please don't report bugs to us.
For building yourself, read on. You'll have to install clang and build clazy from source.
$ brew install --with-clang llvm
$ export CXX=clang++
$ export LLVM_ROOT=/usr/local/opt/llvm
$ cmake
$ make
$ make install
Note: Wherever clazy is mentioned, replace with clazy-cl.bat if you're on Windows, or replace with Clazy-x86_64.AppImage if you're using AppImage.
Note: If you prefer running clazy over a JSON compilation database instead of using it as a plugin, jump to clazy-standalone.
You should now have the clazy command available to you, in <prefix>/bin/.
Compile your programs with it instead of clang++/g++.
Note that this command is just a convenience wrapper which calls:
clang++ -Xclang -load -Xclang ClazyPlugin.so -Xclang -add-plugin -Xclang clazy
If you have multiple versions of clang installed (say clang++-3.8 and clang++-3.9)
you can choose which one to use by setting the CLANGXX environment variable, like so:
export CLANGXX=clang++-3.8; clazy
To build a CMake project use:
cmake . -DCMAKE_CXX_COMPILER=clazy
and rebuild.
To make it the compiler for qmake projects, just run qmake like:
qmake -spec linux-clang QMAKE_CXX="clazy"
On Windows with MSVC it's simply: qmake QMAKE_CXX="clazy-cl.bat"
Alternatively, if you want to use clang directly, without the wrapper:
qmake -spec linux-clang QMAKE_CXXFLAGS="-Xclang -load -Xclang ClazyPlugin.so -Xclang -add-plugin -Xclang clazy"
On Windows it's similar, just inspect the contents of clazy-cl.bat.
It's recommended that you disable pre-compiled headers and don't use ccache.
You're all set, clazy will now run some checks on your project, but not all of them. Read on if you want to enable/disable which checks are run.
There are many checks and they are divided in levels:
- level0: Very stable checks, 99.99% safe, mostly no false-positives, very desirable
- level1: The default level. Very similar to level 0, slightly more false-positives but very few.
- level2: Also very few false-positives, but contains noisy checks which not everyone agree should be default.
- manual: Checks here need to be enabled explicitly, as they don't belong to any level. They can be very stable or very unstable.
clazy runs all checks from level1 by default.
-
Checks from Manual Level:
- assert-with-side-effects
- container-inside-loop
- detaching-member
- heap-allocated-small-trivial-type
- ifndef-define-typo
- inefficient-qlist
- isempty-vs-count
- qhash-with-char-pointer-key
- qproperty-type-mismatch
- qrequiredresult-candidates
- qstring-varargs
- qt-keywords (fix-qt-keywords)
- qt4-qstring-from-array (fix-qt4-qstring-from-array)
- qt6-qlatin1string-to-u
- qvariant-template-instantiation
- raw-environment-function
- reserve-candidates
- signal-with-return-value
- thread-with-slots
- tr-non-literal
- unneeded-cast
-
Checks from Level 0:
- connect-by-name
- connect-non-signal
- connect-not-normalized
- container-anti-pattern
- empty-qstringliteral
- fully-qualified-moc-types
- lambda-in-connect
- lambda-unique-connection
- lowercase-qml-type-name
- mutable-container-key
- overloaded-signal
- qcolor-from-literal
- qdatetime-utc (fix-qdatetime-utc)
- qenums
- qfileinfo-exists
- qgetenv (fix-qgetenv)
- qmap-with-pointer-key
- qstring-arg
- qstring-insensitive-allocation
- qstring-ref (fix-missing-qstringref)
- qt-macros
- strict-iterators
- temporary-iterator
- unused-non-trivial-variable
- writing-to-temporary
- wrong-qevent-cast
- wrong-qglobalstatic
-
Checks from Level 1:
- auto-unexpected-qstringbuilder (fix-auto-unexpected-qstringbuilder)
- child-event-qobject-cast
- connect-3arg-lambda
- const-signal-or-slot
- detaching-temporary
- foreach
- incorrect-emit
- inefficient-qlist-soft
- install-event-filter
- non-pod-global-static
- overridden-signal
- post-event
- qdeleteall
- qhash-namespace
- qlatin1string-non-ascii
- qproperty-without-notify
- qstring-left
- range-loop (fix-range-loop-add-ref,fix-range-loop-add-qasconst)
- returning-data-from-temporary
- rule-of-two-soft
- skipped-base-method
- virtual-signal
-
Checks from Level 2:
- base-class-event
- copyable-polymorphic
- ctor-missing-parent-argument
- function-args-by-ref (fix-function-args-by-ref)
- function-args-by-value
- global-const-char-pointer
- implicit-casts
- missing-qobject-macro
- missing-typeinfo
- old-style-connect (fix-old-style-connect)
- qstring-allocations (fix-qlatin1string-allocations,fix-fromLatin1_fromUtf8-allocations,fix-fromCharPtrAllocations)
- returning-void-expression
- rule-of-three
- static-pmf
- virtual-call-ctor
You may want to choose which checks to enable before starting to compile.
If you don't specify anything then all checks from level0 and level1 will run.
To specify a list of checks to run, or to choose a level, you can use the CLAZY_CHECKS env variable or pass arguments to the compiler.
You can disable checks by prefixing with no-, in case you don't want all checks from a given level.
export CLAZY_CHECKS="unneeded-cast,qmap-with-pointer-key,virtual-call-ctor" # Enables only these 3 checks
export CLAZY_CHECKS="level0,no-qenums" # Enables all checks from level0, except for qenums
export CLAZY_CHECKS="level0,detaching-temporary" # Enables all from level0 and also detaching-temporary
clazy -Xclang -plugin-arg-clazy -Xclang level0,detaching-temporary
Don't forget to re-run cmake/qmake/etc if you altered the c++ flags to specify flags.
The clazy-standalone binary allows you to run clazy over a compilation database JSON file, in the same
way you would use clang-tidy or other clang tooling. This way you don't need to build your application,
only the static analysis is performed.
Note: If you're using the AppImage, use Clazy-x86_64.AppImage --standalone instead of clazy-standalone.
clazy-standalone supports the same env variables as the clazy plugin. You can also specify a list of checks via
the -checks argument.
Running on one cpp file:
clazy-standalone -checks=install-event-filter,qmap-with-pointer-key,level0 -p compile_commands.json my.file.cpp
Running on all cpp files:
find . -name "*cpp" | xargs clazy-standalone -checks=level2 -p default/compile_commands.json
See https://clang.llvm.org/docs/JSONCompilationDatabase.html for how to generate the compile_commands.json file. Basically it's generated
by passing -DCMAKE_EXPORT_COMPILE_COMMANDS to CMake, or using Bear to intercept compiler commands, or, if you're using qbs:
qbs generate --generator clangdb
Note: Be sure the clazy-standalone binary is located in the same folder as the clang binary, otherwise it will have trouble finding builtin headers, like stddef.h. Alternatively, you can symlink to the folder containing the builtin headers:
(Assuming clazy was built with -DCMAKE_INSTALL_PREFIX=/myprefix/)
$ touch foo.c && clang++ '-###' -c foo.c 2>&1 | tr ' ' '\n' | grep -A1 resource
"-resource-dir"
"/usr/bin/../lib/clang/4.0.1" # this is the interesting path (without the version)
$ ln -sf /usr/bin/../lib/clang/ /myprefix/lib/clang
$ ln -sf /usr/bin/../include/c++/ /myprefix/include/c++ # Required on macOS
If that doesn't work, run clang -v and check what's the InstalledDir. Move clazy-standalone to that folder.
clang-tidy support will be added after https://bugs.llvm.org//show_bug.cgi?id=32739 is fixed.
Some checks support fixits, in which clazy will help re-write your source files whenever it can fix something.
Simply pass -Xclang -plugin-arg-clazy -Xclang export-fixes to clang, or -export-fixes=somefile.yaml for clazy-standalone.
Alternatively, set the CLAZY_EXPORT_FIXES env variable (works only with the plugin, not with standalone).
Then run clang-apply-replacements <folder_with_yaml_files>, which will modify your code.
When using fixits, prefer to run only a single check each time, so they don't conflict with each other modifying the same source lines.
WARNING: Backup your code and make sure all changes done by clazy are correct.
-
clang: symbol lookup error:
/usr/lib/x86_64-linux-gnu/ClazyPlugin.so: undefined symbol: _ZNK5clang15DeclarationName11getAsStringEv. This is due to mixing ABIs. Your clang/llvm was compiled with the new gcc c++ ABI but you compiled the clazy plugin with clang (which uses the old ABI).The solution is to build the clazy plugin with gcc or use a distro which hasn't migrated to gcc5 ABI yet, such as archlinux.
-
[Fedora] cmake can't find LLVM ? Try building llvm/clang yourself (There are reports that /usr/share/llvm/cmake/LLVM-Config.cmake is buggy).
-
[Fedora] CommandLine Error:
Option 'opt-bisect-limit' registered more than once!Remove the llvm-static package and use the dynamically linked libraries instead. Alternatively, if you want to use llvm-static, see next item. -
CommandLine Error:
Option 'foo' registered more than once!Means you're building against a static version of LLVM (*.a files instead of *.so). Try passing to cmake -DLINK_CLAZY_TO_LLVM=OFF when building clazy, this was tested successfully against a static LLVM 7.0, and might work with other versions. -
Some checks are mysteriously not producing warnings or not applying fixits ? Check if you have ccache interfering and turn it off.
-
fatal error: 'stddef.h' file not found, while using
clazy-standaloneBe sure the clazy-standalone binary is located in the same folder as the clang binary. -
Be sure to disable pch.
-
macOS: Be sure you're not using Apple Clang
-
Windows: fatal error LNK1112: module machine type ‘X86’ conflicts with target machine type ‘x64’ If you're building in 32-bit, open clazy-cl.bat and insert a -m32 argument. Should read: %~dp0\clang\clang.exe –driver-mode=cl -m32 (...)
When running on codebases that must still compile with Qt4, you can pass --qt4compat
(a convenience option equivalent to passing -Xclang -plugin-arg-clazy -Xclang qt4-compat)
to disable checks that only make sense with Qt5.
For example, to build a CMake project with Qt4 compatibility use:
CXX="clazy --qt4compat"; cmake .
and rebuild.
If you think you found a false-positive, file a bug report. But do make sure to test first without icecc/distcc enabled.
If you want to suppress warnings from headers of Qt or 3rd party code, include them with -isystem instead of -I (gcc/clang only).
For MSVC use /external, which is available since VS 15.6.
Alternatively you can set the CLAZY_HEADER_FILTER env variable to a regexp matching the path where you want warnings,
for example CLAZY_HEADER_FILTER=.*myapplication.*.
You can also exclude paths using a regexp by setting CLAZY_IGNORE_DIRS, for example CLAZY_IGNORE_DIRS=.*my_qt_folder.*.
You can also suppress individual warnings by file or by line by inserting comments:
-
To disable clazy in a specific source file, insert this comment, anywhere in the file:
// clazy:skip -
To disable specific checks in a source file, insert a comment such as
// clazy:excludeall=check1,check2 -
To disable specific checks in specific source lines, insert a comment in the same line as the warning:
(...) // clazy:exclude=check1,check2
Don't include the clazy- prefix. If, for example, you want to disable qstring-allocations you would write:
// clazy:exclude=qstring-allocations not clazy-qstring-allocations.
- bug tracker: https://bugs.kde.org/enter_bug.cgi?product=clazy
- IRC: #kde-clazy (freenode)
- E-mail:
- Sérgio Martins
with contributions from:
- Allen Winter
- Kevin Funk
- Mathias Hasselmann
- Laurent Montel
- Albert Astals Cid
- Aurélien Gâteau
- Hannah von Reth
- Volker Krause
- Christian Ehrlicher
- Christian Gagneraud
- Nikolai Kosjar
and thanks to:
- Klarälvdalens Datakonsult AB (http://www.kdab.com), for letting me work on clazy as a research project
New features go to master and bug fixes go to the 1.6 branch. The prefered way to contributing is by using KDE's phabricator, see:
If you rather just create a pull request in https://github.com/KDE/clazy for a drive-by change, it's also fine, but beware that the maintainer might forget to check on github and the KDE bot will close the PR. In that case just send a reminder to the maintainer (smartins at kde.org).