Index: docs/clang-tidy/Contributing.rst =================================================================== --- /dev/null +++ docs/clang-tidy/Contributing.rst @@ -0,0 +1,507 @@ +================ +Getting Involved +================ + +:program:`clang-tidy` has several own checks and can run Clang static analyzer +checks, but its power is in the ability to easily write custom checks. + +Checks are organized in modules, which can be linked into :program:`clang-tidy` +with minimal or no code changes in :program:`clang-tidy`. + +Checks can plug into the analysis on the preprocessor level using `PPCallbacks`_ +or on the AST level using `AST Matchers`_. When an error is found, checks can +report them in a way similar to how Clang diagnostics work. A fix-it hint can be +attached to a diagnostic message. + +The interface provided by :program:`clang-tidy` makes it easy to write useful +and precise checks in just a few lines of code. If you have an idea for a good +check, the rest of this document explains how to do this. + +There are a few tools particularly useful when developing clang-tidy checks: + * ``add_new_check.py`` is a script to automate the process of adding a new + check, it will create the check, update the CMake file and create a test; + * ``rename_check.py`` does what the script name suggests, renames an existing + check; + * :program:`clang-query` is invaluable for interactive prototyping of AST + matchers and exploration of the Clang AST; + * `clang-check`_ with the ``-ast-dump`` (and optionally ``-ast-dump-filter``) + provides a convenient way to dump AST of a C++ program. + +If CMake is configured with ``CLANG_ENABLE_STATIC_ANALYZER``, +:program:`clang-tidy` will not be built with support for the +``clang-analyzer-*`` checks or the ``mpi-*`` checks. + + +.. _AST Matchers: http://clang.llvm.org/docs/LibASTMatchers.html +.. _PPCallbacks: http://clang.llvm.org/doxygen/classclang_1_1PPCallbacks.html +.. _clang-check: http://clang.llvm.org/docs/ClangCheck.html + + +Choosing the Right Place for your Check +--------------------------------------- + +If you have an idea of a check, you should decide whether it should be +implemented as a: + ++ *Clang diagnostic*: if the check is generic enough, targets code patterns that + most probably are bugs (rather than style or readability issues), can be + implemented effectively and with extremely low false positive rate, it may + make a good Clang diagnostic. + ++ *Clang static analyzer check*: if the check requires some sort of control flow + analysis, it should probably be implemented as a static analyzer check. + ++ *clang-tidy check* is a good choice for linter-style checks, checks that are + related to a certain coding style, checks that address code readability, etc. + + +Preparing your Workspace +------------------------ + +If you are new to LLVM development, you should read the `Getting Started with +the LLVM System`_, `Using Clang Tools`_ and `How To Setup Tooling For LLVM`_ +documents to check out and build LLVM, Clang and Clang Extra Tools with CMake. + +Once you are done, change to the ``llvm/tools/clang/tools/extra`` directory, and +let's start! + +.. _Getting Started with the LLVM System: http://llvm.org/docs/GettingStarted.html +.. _Using Clang Tools: http://clang.llvm.org/docs/ClangTools.html + + +The Directory Structure +----------------------- + +:program:`clang-tidy` source code resides in the +``llvm/tools/clang/tools/extra`` directory and is structured as follows: + +:: + + clang-tidy/ # Clang-tidy core. + |-- ClangTidy.h # Interfaces for users and checks. + |-- ClangTidyModule.h # Interface for clang-tidy modules. + |-- ClangTidyModuleRegistry.h # Interface for registering of modules. + ... + |-- google/ # Google clang-tidy module. + |-+ + |-- GoogleTidyModule.cpp + |-- GoogleTidyModule.h + ... + |-- llvm/ # LLVM clang-tidy module. + |-+ + |-- LLVMTidyModule.cpp + |-- LLVMTidyModule.h + ... + |-- objc/ # Objective-C clang-tidy module. + |-+ + |-- ObjCTidyModule.cpp + |-- ObjCTidyModule.h + ... + |-- tool/ # Sources of the clang-tidy binary. + ... + test/clang-tidy/ # Integration tests. + ... + unittests/clang-tidy/ # Unit tests. + |-- ClangTidyTest.h + |-- GoogleModuleTest.cpp + |-- LLVMModuleTest.cpp + |-- ObjCModuleTest.cpp + ... + + +Writing a clang-tidy Check +-------------------------- + +So you have an idea of a useful check for :program:`clang-tidy`. + +First, if you're not familiar with LLVM development, read through the `Getting +Started with LLVM`_ document for instructions on setting up your workflow and +the `LLVM Coding Standards`_ document to familiarize yourself with the coding +style used in the project. For code reviews we mostly use `LLVM Phabricator`_. + +.. _Getting Started with LLVM: http://llvm.org/docs/GettingStarted.html +.. _LLVM Coding Standards: http://llvm.org/docs/CodingStandards.html +.. _LLVM Phabricator: http://llvm.org/docs/Phabricator.html + +Next, you need to decide which module the check belongs to. Modules +are located in subdirectories of `clang-tidy/ +`_ +and contain checks targeting a certain aspect of code quality (performance, +readability, etc.), certain coding style or standard (Google, LLVM, CERT, etc.) +or a widely used API (e.g. MPI). Their names are same as user-facing check +groups names described :ref:`above `. + +After choosing the module and the name for the check, run the +``clang-tidy/add_new_check.py`` script to create the skeleton of the check and +plug it to :program:`clang-tidy`. It's the recommended way of adding new checks. + +If we want to create a `readability-awesome-function-names`, we would run: + +.. code-block:: console + + $ clang-tidy/add_new_check.py readability awesome-function-names + + +The ``add_new_check.py`` script will: + * create the class for your check inside the specified module's directory and + register it in the module and in the build system; + * create a lit test file in the ``test/clang-tidy/`` directory; + * create a documentation file and include it into the + ``docs/clang-tidy/checks/list.rst``. + +Let's see in more detail at the check class definition: + +.. code-block:: c++ + + ... + + #include "../ClangTidy.h" + + namespace clang { + namespace tidy { + namespace readability { + + ... + class AwesomeFunctionNamesCheck : public ClangTidyCheck { + public: + AwesomeFunctionNamesCheck(StringRef Name, ClangTidyContext *Context) + : ClangTidyCheck(Name, Context) {} + void registerMatchers(ast_matchers::MatchFinder *Finder) override; + void check(const ast_matchers::MatchFinder::MatchResult &Result) override; + }; + + } // namespace readability + } // namespace tidy + } // namespace clang + + ... + +Constructor of the check receives the ``Name`` and ``Context`` parameters, and +must forward them to the ``ClangTidyCheck`` constructor. + +In our case the check needs to operate on the AST level and it overrides the +``registerMatchers`` and ``check`` methods. If we wanted to analyze code on the +preprocessor level, we'd need instead to override the ``registerPPCallbacks`` +method. + +In the ``registerMatchers`` method we create an AST Matcher (see `AST Matchers`_ +for more information) that will find the pattern in the AST that we want to +inspect. The results of the matching are passed to the ``check`` method, which +can further inspect them and report diagnostics. + +.. code-block:: c++ + + using namespace ast_matchers; + + void AwesomeFunctionNamesCheck::registerMatchers(MatchFinder *Finder) { + Finder->addMatcher(functionDecl().bind("x"), this); + } + + void AwesomeFunctionNamesCheck::check(const MatchFinder::MatchResult &Result) { + const auto *MatchedDecl = Result.Nodes.getNodeAs("x"); + if (MatchedDecl->getName().startswith("awesome_")) + return; + diag(MatchedDecl->getLocation(), "function %0 is insufficiently awesome") + << MatchedDecl + << FixItHint::CreateInsertion(MatchedDecl->getLocation(), "awesome_"); + } + +(If you want to see an example of a useful check, look at +`clang-tidy/google/ExplicitConstructorCheck.h +`_ +and `clang-tidy/google/ExplicitConstructorCheck.cpp +`_). + + +Registering your Check +---------------------- + +(The ``add_new_check.py`` takes care of registering the check in an existing +module. If you want to create a new module or know the details, read on.) + +The check should be registered in the corresponding module with a distinct name: + +.. code-block:: c++ + + class MyModule : public ClangTidyModule { + public: + void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override { + CheckFactories.registerCheck( + "my-explicit-constructor"); + } + }; + +Now we need to register the module in the ``ClangTidyModuleRegistry`` using a +statically initialized variable: + +.. code-block:: c++ + + static ClangTidyModuleRegistry::Add X("my-module", + "Adds my lint checks."); + + +When using LLVM build system, we need to use the following hack to ensure the +module is linked into the :program:`clang-tidy` binary: + +Add this near the ``ClangTidyModuleRegistry::Add`` variable: + +.. code-block:: c++ + + // This anchor is used to force the linker to link in the generated object file + // and thus register the MyModule. + volatile int MyModuleAnchorSource = 0; + +And this to the main translation unit of the :program:`clang-tidy` binary (or +the binary you link the ``clang-tidy`` library in) +``clang-tidy/tool/ClangTidyMain.cpp``: + +.. code-block:: c++ + + // This anchor is used to force the linker to link the MyModule. + extern volatile int MyModuleAnchorSource; + static int MyModuleAnchorDestination = MyModuleAnchorSource; + + +Configuring Checks +------------------ + +If a check needs configuration options, it can access check-specific options +using the ``Options.get("SomeOption", DefaultValue)`` call in the check +constructor. In this case the check should also override the +``ClangTidyCheck::storeOptions`` method to make the options provided by the +check discoverable. This method lets :program:`clang-tidy` know which options +the check implements and what the current values are (e.g. for the +``-dump-config`` command line option). + +.. code-block:: c++ + + class MyCheck : public ClangTidyCheck { + const unsigned SomeOption1; + const std::string SomeOption2; + + public: + MyCheck(StringRef Name, ClangTidyContext *Context) + : ClangTidyCheck(Name, Context), + SomeOption(Options.get("SomeOption1", -1U)), + SomeOption(Options.get("SomeOption2", "some default")) {} + + void storeOptions(ClangTidyOptions::OptionMap &Opts) override { + Options.store(Opts, "SomeOption1", SomeOption1); + Options.store(Opts, "SomeOption2", SomeOption2); + } + ... + +Assuming the check is registered with the name "my-check", the option can then +be set in a ``.clang-tidy`` file in the following way: + +.. code-block:: yaml + + CheckOptions: + - key: my-check.SomeOption1 + value: 123 + - key: my-check.SomeOption2 + value: 'some other value' + +If you need to specify check options on a command line, you can use the inline +YAML format: + +.. code-block:: console + + $ clang-tidy -config="{CheckOptions: [{key: a, value: b}, {key: x, value: y}]}" ... + + +Testing Checks +-------------- + +To run tests for :program:`clang-tidy` use the command: + +.. code-block:: console + + $ ninja check-clang-tools + +:program:`clang-tidy` checks can be tested using either unit tests or +`lit`_ tests. Unit tests may be more convenient to test complex replacements +with strict checks. `Lit`_ tests allow using partial text matching and regular +expressions which makes them more suitable for writing compact tests for +diagnostic messages. + +The ``check_clang_tidy.py`` script provides an easy way to test both +diagnostic messages and fix-its. It filters out ``CHECK`` lines from the test +file, runs :program:`clang-tidy` and verifies messages and fixes with two +separate `FileCheck`_ invocations: once with FileCheck's directive +prefix set to ``CHECK-MESSAGES``, validating the diagnostic messages, +and once with the directive prefix set to ``CHECK-FIXES``, running +against the fixed code (i.e., the code after generated fix-its are +applied). In particular, ``CHECK-FIXES:`` can be used to check +that code was not modified by fix-its, by checking that it is present +unchanged in the fixed code. The full set of `FileCheck`_ directives +is available (e.g., ``CHECK-MESSAGES-SAME:``, ``CHECK-MESSAGES-NOT:``), though +typically the basic ``CHECK`` forms (``CHECK-MESSAGES`` and ``CHECK-FIXES``) +are sufficient for clang-tidy tests. Note that the `FileCheck`_ +documentation mostly assumes the default prefix (``CHECK``), and hence +describes the directive as ``CHECK:``, ``CHECK-SAME:``, ``CHECK-NOT:``, etc. +Replace ``CHECK`` by either ``CHECK-FIXES`` or ``CHECK-MESSAGES`` for +clang-tidy tests. + +An additional check enabled by ``check_clang_tidy.py`` ensures that +if `CHECK-MESSAGES:` is used in a file then every warning or error +must have an associated CHECK in that file. Or, you can use ``CHECK-NOTES:`` +instead, if you want to **also** ensure that all the notes are checked. + +To use the ``check_clang_tidy.py`` script, put a .cpp file with the +appropriate ``RUN`` line in the ``test/clang-tidy`` directory. Use +``CHECK-MESSAGES:`` and ``CHECK-FIXES:`` lines to write checks against +diagnostic messages and fixed code. + +It's advised to make the checks as specific as possible to avoid checks matching +to incorrect parts of the input. Use ``[[@LINE+X]]``/``[[@LINE-X]]`` +substitutions and distinct function and variable names in the test code. + +Here's an example of a test using the ``check_clang_tidy.py`` script (the full +source code is at `test/clang-tidy/google-readability-casting.cpp`_): + +.. code-block:: c++ + + // RUN: %check_clang_tidy %s google-readability-casting %t + + void f(int a) { + int b = (int)a; + // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: redundant cast to the same type [google-readability-casting] + // CHECK-FIXES: int b = a; + } + +To check more than one scenario in the same test file use +``-check-suffix=SUFFIX-NAME`` on ``check_clang_tidy.py`` command line or +``-check-suffixes=SUFFIX-NAME-1,SUFFIX-NAME-2,...``. +With ``-check-suffix[es]=SUFFIX-NAME`` you need to replace your ``CHECK-*`` +directives with ``CHECK-MESSAGES-SUFFIX-NAME`` and ``CHECK-FIXES-SUFFIX-NAME``. + +Here's an example: + +.. code-block:: c++ + + // RUN: %check_clang_tidy -check-suffix=USING-A %s misc-unused-using-decls %t -- -- -DUSING_A + // RUN: %check_clang_tidy -check-suffix=USING-B %s misc-unused-using-decls %t -- -- -DUSING_B + // RUN: %check_clang_tidy %s misc-unused-using-decls %t + ... + // CHECK-MESSAGES-USING-A: :[[@LINE-8]]:10: warning: using decl 'A' {{.*}} + // CHECK-MESSAGES-USING-B: :[[@LINE-7]]:10: warning: using decl 'B' {{.*}} + // CHECK-MESSAGES: :[[@LINE-6]]:10: warning: using decl 'C' {{.*}} + // CHECK-FIXES-USING-A-NOT: using a::A;$ + // CHECK-FIXES-USING-B-NOT: using a::B;$ + // CHECK-FIXES-NOT: using a::C;$ + + +There are many dark corners in the C++ language, and it may be difficult to make +your check work perfectly in all cases, especially if it issues fix-it hints. The +most frequent pitfalls are macros and templates: + +1. code written in a macro body/template definition may have a different meaning + depending on the macro expansion/template instantiation; +2. multiple macro expansions/template instantiations may result in the same code + being inspected by the check multiple times (possibly, with different + meanings, see 1), and the same warning (or a slightly different one) may be + issued by the check multiple times; :program:`clang-tidy` will deduplicate + _identical_ warnings, but if the warnings are slightly different, all of them + will be shown to the user (and used for applying fixes, if any); +3. making replacements to a macro body/template definition may be fine for some + macro expansions/template instantiations, but easily break some other + expansions/instantiations. + +.. _lit: http://llvm.org/docs/CommandGuide/lit.html +.. _FileCheck: http://llvm.org/docs/CommandGuide/FileCheck.html +.. _test/clang-tidy/google-readability-casting.cpp: http://reviews.llvm.org/diffusion/L/browse/clang-tools-extra/trunk/test/clang-tidy/google-readability-casting.cpp + + +Running clang-tidy on LLVM +-------------------------- + +To test a check it's best to try it out on a larger code base. LLVM and Clang +are the natural targets as you already have the source code around. The most +convenient way to run :program:`clang-tidy` is with a compile command database; +CMake can automatically generate one, for a description of how to enable it see +`How To Setup Tooling For LLVM`_. Once ``compile_commands.json`` is in place and +a working version of :program:`clang-tidy` is in ``PATH`` the entire code base +can be analyzed with ``clang-tidy/tool/run-clang-tidy.py``. The script executes +:program:`clang-tidy` with the default set of checks on every translation unit +in the compile command database and displays the resulting warnings and errors. +The script provides multiple configuration flags. + +* The default set of checks can be overridden using the ``-checks`` argument, + taking the identical format as :program:`clang-tidy` does. For example + ``-checks=-*,modernize-use-override`` will run the ``modernize-use-override`` + check only. + +* To restrict the files examined you can provide one or more regex arguments + that the file names are matched against. + ``run-clang-tidy.py clang-tidy/.*Check\.cpp`` will only analyze clang-tidy + checks. It may also be necessary to restrict the header files warnings are + displayed from using the ``-header-filter`` flag. It has the same behavior + as the corresponding :program:`clang-tidy` flag. + +* To apply suggested fixes ``-fix`` can be passed as an argument. This gathers + all changes in a temporary directory and applies them. Passing ``-format`` + will run clang-format over changed lines. + + +On checks profiling +------------------- + +:program:`clang-tidy` can collect per-check profiling info, and output it +for each processed source file (translation unit). + +To enable profiling info collection, use the ``-enable-check-profile`` argument. +The timings will be output to ``stderr`` as a table. Example output: + +.. code-block:: console + + $ clang-tidy -enable-check-profile -checks=-*,readability-function-size source.cpp + ===-------------------------------------------------------------------------=== + clang-tidy checks profiling + ===-------------------------------------------------------------------------=== + Total Execution Time: 1.0282 seconds (1.0258 wall clock) + + ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name --- + 0.9136 (100.0%) 0.1146 (100.0%) 1.0282 (100.0%) 1.0258 (100.0%) readability-function-size + 0.9136 (100.0%) 0.1146 (100.0%) 1.0282 (100.0%) 1.0258 (100.0%) Total + +It can also store that data as JSON files for further processing. Example output: + +.. code-block:: console + + $ clang-tidy -enable-check-profile -store-check-profile=. -checks=-*,readability-function-size source.cpp + $ # Note that there won't be timings table printed to the console. + $ ls /tmp/out/ + 20180516161318717446360-source.cpp.json + $ cat 20180516161318717446360-source.cpp.json + { + "file": "/path/to/source.cpp", + "timestamp": "2018-05-16 16:13:18.717446360", + "profile": { + "time.clang-tidy.readability-function-size.wall": 1.0421266555786133e+00, + "time.clang-tidy.readability-function-size.user": 9.2088400000005421e-01, + "time.clang-tidy.readability-function-size.sys": 1.2418899999999974e-01 + } + } + +There is only one argument that controls profile storage: + +* ``-store-check-profile=`` + + By default reports are printed in tabulated format to stderr. When this option + is passed, these per-TU profiles are instead stored as JSON. + If the prefix is not an absolute path, it is considered to be relative to the + directory from where you have run :program:`clang-tidy`. All ``.`` and ``..`` + patterns in the path are collapsed, and symlinks are resolved. + + Example: + Let's suppose you have a source file named ``example.cpp``, located in the + ``/source`` directory. Only the input filename is used, not the full path + to the source file. Additionally, it is prefixed with the current timestamp. + + * If you specify ``-store-check-profile=/tmp``, then the profile will be saved + to ``/tmp/-example.cpp.json`` + + * If you run :program:`clang-tidy` from within ``/foo`` directory, and specify + ``-store-check-profile=.``, then the profile will still be saved to + ``/foo/-example.cpp.json`` Index: docs/clang-tidy/Integrations.rst =================================================================== --- /dev/null +++ docs/clang-tidy/Integrations.rst @@ -0,0 +1,117 @@ +================================== +Clang-tidy IDE/Editor Integrations +================================== + +.. _Clangd: https://clang.llvm.org/extra/clangd.html + +Apart from being a standalone tool, :program:`clang-tidy` is integrated into +various IDEs, code analyzers, and editors. Besides, it is currently being +integrated into Clangd_. The following table shows the most +well-known :program:`clang-tidy` integrations in detail. + ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +| | Feature | ++======================================+========================+=================================+==========================+=========================================+==========================+ +| **Tool** | On-the-fly inspection | Check list configuration (GUI) | Options to checks (GUI) | Configuration via ``.clang-tidy`` files | Custom clang-tidy binary | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|A.L.E. for Vim | \+\ | \-\ | \-\ | \-\ | \+\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|Clang Power Tools for Visual Studio | \-\ | \+\ | \-\ | \+\ | \-\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|Clangd | \+\ | \-\ | \-\ | \-\ | \-\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|CLion IDE | \+\ | \+\ | \+\ | \+\ | \+\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|CodeChecker | \-\ | \-\ | \-\ | \-\ | \+\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|CPPCheck | \-\ | \-\ | \-\ | \-\ | \-\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|CPPDepend | \-\ | \-\ | \-\ | \-\ | \-\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|Flycheck for Emacs | \+\ | \-\ | \-\ | \+\ | \+\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|KDevelop IDE | \-\ | \+\ | \+\ | \+\ | \+\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|Qt Creator IDE | \+\ | \+\ | \-\ | \-\ | \+\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|ReSharper C++ for Visual Studio | \+\ | \+\ | \-\ | \+\ | \-\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|Syntastic for Vim | \+\ | \-\ | \-\ | \-\ | \+\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ +|Visual Assist for Visual Studio | \+\ | \+\ | \-\ | \-\ | \-\ | ++--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ + +**IDEs** + +.. _CLion: https://www.jetbrains.com/clion/ +.. _integrates clang-tidy: https://www.jetbrains.com/help/clion/clang-tidy-checks-support.html + +CLion_ 2017.2 and later `integrates clang-tidy`_ as an extension to the +built-in code analyzer. Starting from 2018.2 EAP, CLion allows using +:program:`clang-tidy` via Clangd. Inspections and applicable quick-fixes are +performed on the fly, and checks can be configured in standard command line +format. In this integration, you can switch to the :program:`clang-tidy` +binary different from the bundled one, pass the configuration in +``.clang-tidy`` files instead of using the IDE settings, and configure +options for particular checks. + +.. _KDevelop: https://www.kdevelop.org/ +.. _kdev-clang-tidy: https://github.com/KDE/kdev-clang-tidy/ + +KDevelop_ with the kdev-clang-tidy_ plugin, starting from version 5.1, performs +static analysis using :program:`clang-tidy`. The plugin launches the +:program:`clang-tidy` binary from the specified location and parses its +output to provide a list of issues. + +.. _QtCreator: https://www.qt.io/ +.. _Clang Code Model: http://doc.qt.io/qtcreator/creator-clang-codemodel.html + +QtCreator_ 4.6 integrates :program:`clang-tidy` warnings into the editor +diagnostics under the `Clang Code Model`_. To employ :program:`clang-tidy` +inspection in QtCreator, you need to create a copy of one of the presets and +choose the checks to be performed in the Clang Code Model Warnings menu. + +.. _MS Visual Studio: https://visualstudio.microsoft.com/ +.. _ReSharper C++: https://www.jetbrains.com/help/resharper/Clang_Tidy_Integration.html +.. _Visual Assist: https://docs.wholetomato.com/default.asp?W761 +.. _Clang Power Tools: https://marketplace.visualstudio.com/items?itemName=caphyon.ClangPowerTools +.. _clang-tidy-vs: https://github.com/llvm-mirror/clang-tools-extra/tree/master/clang-tidy-vs + +`MS Visual Studio`_ has a native clang-tidy-vs_ plugin and also can integrate +:program:`clang-tidy` by means of three other tools. The `ReSharper C++`_ +extension, version 2017.3 and later, provides seamless :program:`clang-tidy` +integration: checks and quick-fixes run alongside native inspections. Apart +from that, ReSharper C++ incorporates :program:`clang-tidy` as a separate +step of its code clean-up process. `Visual Assist`_ build 2210 includes a +subset of :program:`clang-tidy` checklist to inspect the code as you edit. +Another way to bring :program:`clang-tidy` functionality to Visual Studio is +the `Clang Power Tools`_ plugin, which includes most of the +:program:`clang-tidy` checks and runs them during compilation or as a separate +step of code analysis. + +**Editors** + +.. _Flycheck: https://github.com/ch1bo/flycheck-clang-tidy +.. _Syntastic: https://github.com/vim-syntastic/syntastic +.. _A.L.E.: https://github.com/w0rp/ale +.. _Emacs24: https://www.gnu.org/s/emacs/ +.. _Vim: https://www.vim.org/ + +Emacs24_, when expanded with the Flycheck_ plugin, incorporates the +:program:`clang-tidy` inspection into the syntax analyzer. For Vim_, you can +use Syntastic_, which includes :program:`clang-tidy`, or `A.L.E.`_, +a lint engine that applies :program:`clang-tidy` along with other linters. + +**Analyzers** + +.. _CPPDepend: https://www.cppdepend.com/cppdependv2018 +.. _CPPCheck: https://sourceforge.net/p/cppcheck/news/ +.. _CodeChecker: https://github.com/Ericsson/codechecker +.. _plugin: https://github.com/Ericsson/CodeCheckerEclipsePlugin + +:program:`clang-tidy` is integrated in CPPDepend_ starting from version 2018.1 +and CPPCheck_ 1.82. CPPCheck integration lets you import Visual Studio +solutions and run the :program:`clang-tidy` inspection on them. The +CodeChecker_ application of version 5.3 or later, which also comes as a plugin_ +for Eclipse, supports :program:`clang-tidy` as a static analysis instrument and +allows to use a custom :program:`clang-tidy` binary. Index: docs/clang-tidy/index.rst =================================================================== --- docs/clang-tidy/index.rst +++ docs/clang-tidy/index.rst @@ -10,6 +10,8 @@ :maxdepth: 1 The list of clang-tidy checks + Clang-tidy IDE/Editor Integrations + Getting Involved :program:`clang-tidy` is a clang-based C++ "linter" tool. Its purpose is to provide an extensible framework for diagnosing and fixing typical programming @@ -21,9 +23,6 @@ Using clang-tidy ================ -Standalone tool ---------------- - :program:`clang-tidy` is a `LibTooling`_-based tool, and it's easier to work with if you set up a compile command database for your project (for an example of how to do this see `How To Setup Tooling For LLVM`_). You can also specify @@ -259,124 +258,6 @@ ... -Clang-tidy integrated ---------------------- - -.. _Clangd: https://clang.llvm.org/extra/clangd.html - -Apart from being a standalone tool, :program:`clang-tidy` is integrated into -various IDEs, code analyzers, and editors. Besides, it is currently being -integrated into Clangd_. The following table shows the most -well-known :program:`clang-tidy` integrations in detail. - -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -| | Feature | -+======================================+========================+=================================+==========================+=========================================+==========================+ -| **Tool** | On-the-fly inspection | Check list configuration (GUI) | Options to checks (GUI) | Configuration via ``.clang-tidy`` files | Custom clang-tidy binary | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|A.L.E. for Vim | \+\ | \-\ | \-\ | \-\ | \+\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|Clang Power Tools for Visual Studio | \-\ | \+\ | \-\ | \+\ | \-\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|Clangd | \+\ | \-\ | \-\ | \-\ | \-\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|CLion IDE | \+\ | \+\ | \+\ | \+\ | \+\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|CodeChecker | \-\ | \-\ | \-\ | \-\ | \+\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|CPPCheck | \-\ | \-\ | \-\ | \-\ | \-\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|CPPDepend | \-\ | \-\ | \-\ | \-\ | \-\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|Flycheck for Emacs | \+\ | \-\ | \-\ | \+\ | \+\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|KDevelop IDE | \-\ | \+\ | \+\ | \+\ | \+\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|Qt Creator IDE | \+\ | \+\ | \-\ | \-\ | \+\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|ReSharper C++ for Visual Studio | \+\ | \+\ | \-\ | \+\ | \-\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|Syntastic for Vim | \+\ | \-\ | \-\ | \-\ | \+\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ -|Visual Assist for Visual Studio | \+\ | \+\ | \-\ | \-\ | \-\ | -+--------------------------------------+------------------------+---------------------------------+--------------------------+-----------------------------------------+--------------------------+ - - -**IDEs** - -.. _CLion: https://www.jetbrains.com/clion/ -.. _integrates clang-tidy: https://www.jetbrains.com/help/clion/clang-tidy-checks-support.html - -CLion_ 2017.2 and later `integrates clang-tidy`_ as an extension to the -built-in code analyzer. Starting from 2018.2 EAP, CLion allows using -:program:`clang-tidy` via Clangd. Inspections and applicable quick-fixes are -performed on the fly, and checks can be configured in standard command line -format. In this integration, you can switch to the :program:`clang-tidy` -binary different from the bundled one, pass the configuration in -``.clang-tidy`` files instead of using the IDE settings, and configure -options for particular checks. - -.. _KDevelop: https://www.kdevelop.org/ -.. _kdev-clang-tidy: https://github.com/KDE/kdev-clang-tidy/ - -KDevelop_ with the kdev-clang-tidy_ plugin, starting from version 5.1, performs -static analysis using :program:`clang-tidy`. The plugin launches the -:program:`clang-tidy` binary from the specified location and parses its -output to provide a list of issues. - -.. _QtCreator: https://www.qt.io/ -.. _Clang Code Model: http://doc.qt.io/qtcreator/creator-clang-codemodel.html - -QtCreator_ 4.6 integrates :program:`clang-tidy` warnings into the editor -diagnostics under the `Clang Code Model`_. To employ :program:`clang-tidy` -inspection in QtCreator, you need to create a copy of one of the presets and -choose the checks to be performed in the Clang Code Model Warnings menu. - -.. _MS Visual Studio: https://visualstudio.microsoft.com/ -.. _ReSharper C++: https://www.jetbrains.com/help/resharper/Clang_Tidy_Integration.html -.. _Visual Assist: https://docs.wholetomato.com/default.asp?W761 -.. _Clang Power Tools: https://marketplace.visualstudio.com/items?itemName=caphyon.ClangPowerTools -.. _clang-tidy-vs: https://github.com/llvm-mirror/clang-tools-extra/tree/master/clang-tidy-vs - -`MS Visual Studio`_ has a native clang-tidy-vs_ plugin and also can integrate -:program:`clang-tidy` by means of three other tools. The `ReSharper C++`_ -extension, version 2017.3 and later, provides seamless :program:`clang-tidy` -integration: checks and quick-fixes run alongside native inspections. Apart -from that, ReSharper C++ incorporates :program:`clang-tidy` as a separate -step of its code clean-up process. `Visual Assist`_ build 2210 includes a -subset of :program:`clang-tidy` checklist to inspect the code as you edit. -Another way to bring :program:`clang-tidy` functionality to Visual Studio is -the `Clang Power Tools`_ plugin, which includes most of the -:program:`clang-tidy` checks and runs them during compilation or as a separate -step of code analysis. - -**Editors** - -.. _Flycheck: https://github.com/ch1bo/flycheck-clang-tidy -.. _Syntastic: https://github.com/vim-syntastic/syntastic -.. _A.L.E.: https://github.com/w0rp/ale -.. _Emacs24: https://www.gnu.org/s/emacs/ -.. _Vim: https://www.vim.org/ - -Emacs24_, when expanded with the Flycheck_ plugin, incorporates the -:program:`clang-tidy` inspection into the syntax analyzer. For Vim_, you can -use Syntastic_, which includes :program:`clang-tidy`, or `A.L.E.`_, -a lint engine that applies :program:`clang-tidy` along with other linters. - -**Analyzers** - -.. _CPPDepend: https://www.cppdepend.com/cppdependv2018 -.. _CPPCheck: https://sourceforge.net/p/cppcheck/news/ -.. _CodeChecker: https://github.com/Ericsson/codechecker -.. _plugin: https://github.com/Ericsson/CodeCheckerEclipsePlugin - -:program:`clang-tidy` is integrated in CPPDepend_ starting from version 2018.1 -and CPPCheck_ 1.82. CPPCheck integration lets you import Visual Studio -solutions and run the :program:`clang-tidy` inspection on them. The -CodeChecker_ application of version 5.3 or later, which also comes as a plugin_ -for Eclipse, supports :program:`clang-tidy` as a static analysis instrument and -allows to use a custom :program:`clang-tidy` binary. - Suppressing Undesired Diagnostics ================================= @@ -432,511 +313,3 @@ .. _LibTooling: http://clang.llvm.org/docs/LibTooling.html .. _How To Setup Tooling For LLVM: http://clang.llvm.org/docs/HowToSetupToolingForLLVM.html - - -Getting Involved -================ - -:program:`clang-tidy` has several own checks and can run Clang static analyzer -checks, but its power is in the ability to easily write custom checks. - -Checks are organized in modules, which can be linked into :program:`clang-tidy` -with minimal or no code changes in :program:`clang-tidy`. - -Checks can plug into the analysis on the preprocessor level using `PPCallbacks`_ -or on the AST level using `AST Matchers`_. When an error is found, checks can -report them in a way similar to how Clang diagnostics work. A fix-it hint can be -attached to a diagnostic message. - -The interface provided by :program:`clang-tidy` makes it easy to write useful -and precise checks in just a few lines of code. If you have an idea for a good -check, the rest of this document explains how to do this. - -There are a few tools particularly useful when developing clang-tidy checks: - * ``add_new_check.py`` is a script to automate the process of adding a new - check, it will create the check, update the CMake file and create a test; - * ``rename_check.py`` does what the script name suggests, renames an existing - check; - * :program:`clang-query` is invaluable for interactive prototyping of AST - matchers and exploration of the Clang AST; - * `clang-check`_ with the ``-ast-dump`` (and optionally ``-ast-dump-filter``) - provides a convenient way to dump AST of a C++ program. - -If CMake is configured with ``CLANG_ENABLE_STATIC_ANALYZER``, -:program:`clang-tidy` will not be built with support for the -``clang-analyzer-*`` checks or the ``mpi-*`` checks. - - -.. _AST Matchers: http://clang.llvm.org/docs/LibASTMatchers.html -.. _PPCallbacks: http://clang.llvm.org/doxygen/classclang_1_1PPCallbacks.html -.. _clang-check: http://clang.llvm.org/docs/ClangCheck.html - - -Choosing the Right Place for your Check ---------------------------------------- - -If you have an idea of a check, you should decide whether it should be -implemented as a: - -+ *Clang diagnostic*: if the check is generic enough, targets code patterns that - most probably are bugs (rather than style or readability issues), can be - implemented effectively and with extremely low false positive rate, it may - make a good Clang diagnostic. - -+ *Clang static analyzer check*: if the check requires some sort of control flow - analysis, it should probably be implemented as a static analyzer check. - -+ *clang-tidy check* is a good choice for linter-style checks, checks that are - related to a certain coding style, checks that address code readability, etc. - - -Preparing your Workspace ------------------------- - -If you are new to LLVM development, you should read the `Getting Started with -the LLVM System`_, `Using Clang Tools`_ and `How To Setup Tooling For LLVM`_ -documents to check out and build LLVM, Clang and Clang Extra Tools with CMake. - -Once you are done, change to the ``llvm/tools/clang/tools/extra`` directory, and -let's start! - -.. _Getting Started with the LLVM System: http://llvm.org/docs/GettingStarted.html -.. _Using Clang Tools: http://clang.llvm.org/docs/ClangTools.html - - -The Directory Structure ------------------------ - -:program:`clang-tidy` source code resides in the -``llvm/tools/clang/tools/extra`` directory and is structured as follows: - -:: - - clang-tidy/ # Clang-tidy core. - |-- ClangTidy.h # Interfaces for users and checks. - |-- ClangTidyModule.h # Interface for clang-tidy modules. - |-- ClangTidyModuleRegistry.h # Interface for registering of modules. - ... - |-- google/ # Google clang-tidy module. - |-+ - |-- GoogleTidyModule.cpp - |-- GoogleTidyModule.h - ... - |-- llvm/ # LLVM clang-tidy module. - |-+ - |-- LLVMTidyModule.cpp - |-- LLVMTidyModule.h - ... - |-- objc/ # Objective-C clang-tidy module. - |-+ - |-- ObjCTidyModule.cpp - |-- ObjCTidyModule.h - ... - |-- tool/ # Sources of the clang-tidy binary. - ... - test/clang-tidy/ # Integration tests. - ... - unittests/clang-tidy/ # Unit tests. - |-- ClangTidyTest.h - |-- GoogleModuleTest.cpp - |-- LLVMModuleTest.cpp - |-- ObjCModuleTest.cpp - ... - - -Writing a clang-tidy Check --------------------------- - -So you have an idea of a useful check for :program:`clang-tidy`. - -First, if you're not familiar with LLVM development, read through the `Getting -Started with LLVM`_ document for instructions on setting up your workflow and -the `LLVM Coding Standards`_ document to familiarize yourself with the coding -style used in the project. For code reviews we mostly use `LLVM Phabricator`_. - -.. _Getting Started with LLVM: http://llvm.org/docs/GettingStarted.html -.. _LLVM Coding Standards: http://llvm.org/docs/CodingStandards.html -.. _LLVM Phabricator: http://llvm.org/docs/Phabricator.html - -Next, you need to decide which module the check belongs to. Modules -are located in subdirectories of `clang-tidy/ -`_ -and contain checks targeting a certain aspect of code quality (performance, -readability, etc.), certain coding style or standard (Google, LLVM, CERT, etc.) -or a widely used API (e.g. MPI). Their names are same as user-facing check -groups names described :ref:`above `. - -After choosing the module and the name for the check, run the -``clang-tidy/add_new_check.py`` script to create the skeleton of the check and -plug it to :program:`clang-tidy`. It's the recommended way of adding new checks. - -If we want to create a `readability-awesome-function-names`, we would run: - -.. code-block:: console - - $ clang-tidy/add_new_check.py readability awesome-function-names - - -The ``add_new_check.py`` script will: - * create the class for your check inside the specified module's directory and - register it in the module and in the build system; - * create a lit test file in the ``test/clang-tidy/`` directory; - * create a documentation file and include it into the - ``docs/clang-tidy/checks/list.rst``. - -Let's see in more detail at the check class definition: - -.. code-block:: c++ - - ... - - #include "../ClangTidy.h" - - namespace clang { - namespace tidy { - namespace readability { - - ... - class AwesomeFunctionNamesCheck : public ClangTidyCheck { - public: - AwesomeFunctionNamesCheck(StringRef Name, ClangTidyContext *Context) - : ClangTidyCheck(Name, Context) {} - void registerMatchers(ast_matchers::MatchFinder *Finder) override; - void check(const ast_matchers::MatchFinder::MatchResult &Result) override; - }; - - } // namespace readability - } // namespace tidy - } // namespace clang - - ... - -Constructor of the check receives the ``Name`` and ``Context`` parameters, and -must forward them to the ``ClangTidyCheck`` constructor. - -In our case the check needs to operate on the AST level and it overrides the -``registerMatchers`` and ``check`` methods. If we wanted to analyze code on the -preprocessor level, we'd need instead to override the ``registerPPCallbacks`` -method. - -In the ``registerMatchers`` method we create an AST Matcher (see `AST Matchers`_ -for more information) that will find the pattern in the AST that we want to -inspect. The results of the matching are passed to the ``check`` method, which -can further inspect them and report diagnostics. - -.. code-block:: c++ - - using namespace ast_matchers; - - void AwesomeFunctionNamesCheck::registerMatchers(MatchFinder *Finder) { - Finder->addMatcher(functionDecl().bind("x"), this); - } - - void AwesomeFunctionNamesCheck::check(const MatchFinder::MatchResult &Result) { - const auto *MatchedDecl = Result.Nodes.getNodeAs("x"); - if (MatchedDecl->getName().startswith("awesome_")) - return; - diag(MatchedDecl->getLocation(), "function %0 is insufficiently awesome") - << MatchedDecl - << FixItHint::CreateInsertion(MatchedDecl->getLocation(), "awesome_"); - } - -(If you want to see an example of a useful check, look at -`clang-tidy/google/ExplicitConstructorCheck.h -`_ -and `clang-tidy/google/ExplicitConstructorCheck.cpp -`_). - - -Registering your Check ----------------------- - -(The ``add_new_check.py`` takes care of registering the check in an existing -module. If you want to create a new module or know the details, read on.) - -The check should be registered in the corresponding module with a distinct name: - -.. code-block:: c++ - - class MyModule : public ClangTidyModule { - public: - void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override { - CheckFactories.registerCheck( - "my-explicit-constructor"); - } - }; - -Now we need to register the module in the ``ClangTidyModuleRegistry`` using a -statically initialized variable: - -.. code-block:: c++ - - static ClangTidyModuleRegistry::Add X("my-module", - "Adds my lint checks."); - - -When using LLVM build system, we need to use the following hack to ensure the -module is linked into the :program:`clang-tidy` binary: - -Add this near the ``ClangTidyModuleRegistry::Add`` variable: - -.. code-block:: c++ - - // This anchor is used to force the linker to link in the generated object file - // and thus register the MyModule. - volatile int MyModuleAnchorSource = 0; - -And this to the main translation unit of the :program:`clang-tidy` binary (or -the binary you link the ``clang-tidy`` library in) -``clang-tidy/tool/ClangTidyMain.cpp``: - -.. code-block:: c++ - - // This anchor is used to force the linker to link the MyModule. - extern volatile int MyModuleAnchorSource; - static int MyModuleAnchorDestination = MyModuleAnchorSource; - - -Configuring Checks ------------------- - -If a check needs configuration options, it can access check-specific options -using the ``Options.get("SomeOption", DefaultValue)`` call in the check -constructor. In this case the check should also override the -``ClangTidyCheck::storeOptions`` method to make the options provided by the -check discoverable. This method lets :program:`clang-tidy` know which options -the check implements and what the current values are (e.g. for the -``-dump-config`` command line option). - -.. code-block:: c++ - - class MyCheck : public ClangTidyCheck { - const unsigned SomeOption1; - const std::string SomeOption2; - - public: - MyCheck(StringRef Name, ClangTidyContext *Context) - : ClangTidyCheck(Name, Context), - SomeOption(Options.get("SomeOption1", -1U)), - SomeOption(Options.get("SomeOption2", "some default")) {} - - void storeOptions(ClangTidyOptions::OptionMap &Opts) override { - Options.store(Opts, "SomeOption1", SomeOption1); - Options.store(Opts, "SomeOption2", SomeOption2); - } - ... - -Assuming the check is registered with the name "my-check", the option can then -be set in a ``.clang-tidy`` file in the following way: - -.. code-block:: yaml - - CheckOptions: - - key: my-check.SomeOption1 - value: 123 - - key: my-check.SomeOption2 - value: 'some other value' - -If you need to specify check options on a command line, you can use the inline -YAML format: - -.. code-block:: console - - $ clang-tidy -config="{CheckOptions: [{key: a, value: b}, {key: x, value: y}]}" ... - - -Testing Checks --------------- - -To run tests for :program:`clang-tidy` use the command: - -.. code-block:: console - - $ ninja check-clang-tools - -:program:`clang-tidy` checks can be tested using either unit tests or -`lit`_ tests. Unit tests may be more convenient to test complex replacements -with strict checks. `Lit`_ tests allow using partial text matching and regular -expressions which makes them more suitable for writing compact tests for -diagnostic messages. - -The ``check_clang_tidy.py`` script provides an easy way to test both -diagnostic messages and fix-its. It filters out ``CHECK`` lines from the test -file, runs :program:`clang-tidy` and verifies messages and fixes with two -separate `FileCheck`_ invocations: once with FileCheck's directive -prefix set to ``CHECK-MESSAGES``, validating the diagnostic messages, -and once with the directive prefix set to ``CHECK-FIXES``, running -against the fixed code (i.e., the code after generated fix-its are -applied). In particular, ``CHECK-FIXES:`` can be used to check -that code was not modified by fix-its, by checking that it is present -unchanged in the fixed code. The full set of `FileCheck`_ directives -is available (e.g., ``CHECK-MESSAGES-SAME:``, ``CHECK-MESSAGES-NOT:``), though -typically the basic ``CHECK`` forms (``CHECK-MESSAGES`` and ``CHECK-FIXES``) -are sufficient for clang-tidy tests. Note that the `FileCheck`_ -documentation mostly assumes the default prefix (``CHECK``), and hence -describes the directive as ``CHECK:``, ``CHECK-SAME:``, ``CHECK-NOT:``, etc. -Replace ``CHECK`` by either ``CHECK-FIXES`` or ``CHECK-MESSAGES`` for -clang-tidy tests. - -An additional check enabled by ``check_clang_tidy.py`` ensures that -if `CHECK-MESSAGES:` is used in a file then every warning or error -must have an associated CHECK in that file. Or, you can use ``CHECK-NOTES:`` -instead, if you want to **also** ensure that all the notes are checked. - -To use the ``check_clang_tidy.py`` script, put a .cpp file with the -appropriate ``RUN`` line in the ``test/clang-tidy`` directory. Use -``CHECK-MESSAGES:`` and ``CHECK-FIXES:`` lines to write checks against -diagnostic messages and fixed code. - -It's advised to make the checks as specific as possible to avoid checks matching -to incorrect parts of the input. Use ``[[@LINE+X]]``/``[[@LINE-X]]`` -substitutions and distinct function and variable names in the test code. - -Here's an example of a test using the ``check_clang_tidy.py`` script (the full -source code is at `test/clang-tidy/google-readability-casting.cpp`_): - -.. code-block:: c++ - - // RUN: %check_clang_tidy %s google-readability-casting %t - - void f(int a) { - int b = (int)a; - // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: redundant cast to the same type [google-readability-casting] - // CHECK-FIXES: int b = a; - } - -To check more than one scenario in the same test file use -``-check-suffix=SUFFIX-NAME`` on ``check_clang_tidy.py`` command line or -``-check-suffixes=SUFFIX-NAME-1,SUFFIX-NAME-2,...``. -With ``-check-suffix[es]=SUFFIX-NAME`` you need to replace your ``CHECK-*`` -directives with ``CHECK-MESSAGES-SUFFIX-NAME`` and ``CHECK-FIXES-SUFFIX-NAME``. - -Here's an example: - -.. code-block:: c++ - - // RUN: %check_clang_tidy -check-suffix=USING-A %s misc-unused-using-decls %t -- -- -DUSING_A - // RUN: %check_clang_tidy -check-suffix=USING-B %s misc-unused-using-decls %t -- -- -DUSING_B - // RUN: %check_clang_tidy %s misc-unused-using-decls %t - ... - // CHECK-MESSAGES-USING-A: :[[@LINE-8]]:10: warning: using decl 'A' {{.*}} - // CHECK-MESSAGES-USING-B: :[[@LINE-7]]:10: warning: using decl 'B' {{.*}} - // CHECK-MESSAGES: :[[@LINE-6]]:10: warning: using decl 'C' {{.*}} - // CHECK-FIXES-USING-A-NOT: using a::A;$ - // CHECK-FIXES-USING-B-NOT: using a::B;$ - // CHECK-FIXES-NOT: using a::C;$ - - -There are many dark corners in the C++ language, and it may be difficult to make -your check work perfectly in all cases, especially if it issues fix-it hints. The -most frequent pitfalls are macros and templates: - -1. code written in a macro body/template definition may have a different meaning - depending on the macro expansion/template instantiation; -2. multiple macro expansions/template instantiations may result in the same code - being inspected by the check multiple times (possibly, with different - meanings, see 1), and the same warning (or a slightly different one) may be - issued by the check multiple times; :program:`clang-tidy` will deduplicate - _identical_ warnings, but if the warnings are slightly different, all of them - will be shown to the user (and used for applying fixes, if any); -3. making replacements to a macro body/template definition may be fine for some - macro expansions/template instantiations, but easily break some other - expansions/instantiations. - -.. _lit: http://llvm.org/docs/CommandGuide/lit.html -.. _FileCheck: http://llvm.org/docs/CommandGuide/FileCheck.html -.. _test/clang-tidy/google-readability-casting.cpp: http://reviews.llvm.org/diffusion/L/browse/clang-tools-extra/trunk/test/clang-tidy/google-readability-casting.cpp - - -Running clang-tidy on LLVM --------------------------- - -To test a check it's best to try it out on a larger code base. LLVM and Clang -are the natural targets as you already have the source code around. The most -convenient way to run :program:`clang-tidy` is with a compile command database; -CMake can automatically generate one, for a description of how to enable it see -`How To Setup Tooling For LLVM`_. Once ``compile_commands.json`` is in place and -a working version of :program:`clang-tidy` is in ``PATH`` the entire code base -can be analyzed with ``clang-tidy/tool/run-clang-tidy.py``. The script executes -:program:`clang-tidy` with the default set of checks on every translation unit -in the compile command database and displays the resulting warnings and errors. -The script provides multiple configuration flags. - -* The default set of checks can be overridden using the ``-checks`` argument, - taking the identical format as :program:`clang-tidy` does. For example - ``-checks=-*,modernize-use-override`` will run the ``modernize-use-override`` - check only. - -* To restrict the files examined you can provide one or more regex arguments - that the file names are matched against. - ``run-clang-tidy.py clang-tidy/.*Check\.cpp`` will only analyze clang-tidy - checks. It may also be necessary to restrict the header files warnings are - displayed from using the ``-header-filter`` flag. It has the same behavior - as the corresponding :program:`clang-tidy` flag. - -* To apply suggested fixes ``-fix`` can be passed as an argument. This gathers - all changes in a temporary directory and applies them. Passing ``-format`` - will run clang-format over changed lines. - - -On checks profiling -------------------- - -:program:`clang-tidy` can collect per-check profiling info, and output it -for each processed source file (translation unit). - -To enable profiling info collection, use the ``-enable-check-profile`` argument. -The timings will be output to ``stderr`` as a table. Example output: - -.. code-block:: console - - $ clang-tidy -enable-check-profile -checks=-*,readability-function-size source.cpp - ===-------------------------------------------------------------------------=== - clang-tidy checks profiling - ===-------------------------------------------------------------------------=== - Total Execution Time: 1.0282 seconds (1.0258 wall clock) - - ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name --- - 0.9136 (100.0%) 0.1146 (100.0%) 1.0282 (100.0%) 1.0258 (100.0%) readability-function-size - 0.9136 (100.0%) 0.1146 (100.0%) 1.0282 (100.0%) 1.0258 (100.0%) Total - -It can also store that data as JSON files for further processing. Example output: - -.. code-block:: console - - $ clang-tidy -enable-check-profile -store-check-profile=. -checks=-*,readability-function-size source.cpp - $ # Note that there won't be timings table printed to the console. - $ ls /tmp/out/ - 20180516161318717446360-source.cpp.json - $ cat 20180516161318717446360-source.cpp.json - { - "file": "/path/to/source.cpp", - "timestamp": "2018-05-16 16:13:18.717446360", - "profile": { - "time.clang-tidy.readability-function-size.wall": 1.0421266555786133e+00, - "time.clang-tidy.readability-function-size.user": 9.2088400000005421e-01, - "time.clang-tidy.readability-function-size.sys": 1.2418899999999974e-01 - } - } - -There is only one argument that controls profile storage: - -* ``-store-check-profile=`` - - By default reports are printed in tabulated format to stderr. When this option - is passed, these per-TU profiles are instead stored as JSON. - If the prefix is not an absolute path, it is considered to be relative to the - directory from where you have run :program:`clang-tidy`. All ``.`` and ``..`` - patterns in the path are collapsed, and symlinks are resolved. - - Example: - Let's suppose you have a source file named ``example.cpp``, located in the - ``/source`` directory. Only the input filename is used, not the full path - to the source file. Additionally, it is prefixed with the current timestamp. - - * If you specify ``-store-check-profile=/tmp``, then the profile will be saved - to ``/tmp/-example.cpp.json`` - - * If you run :program:`clang-tidy` from within ``/foo`` directory, and specify - ``-store-check-profile=.``, then the profile will still be saved to - ``/foo/-example.cpp.json``