<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>LibTooling</title> <link type="text/css" rel="stylesheet" href="../menu.css"> <link type="text/css" rel="stylesheet" href="../content.css"> </head> <body> <!--#include virtual="../menu.html.incl"--> <div id="content"> <h1>LibTooling</h1> <p>LibTooling is a library to support writing standalone tools based on Clang. This document will provide a basic walkthrough of how to write a tool using LibTooling.</p> <p>For the information on how to setup Clang Tooling for LLVM see <a href="HowToSetupToolingForLLVM.html">HowToSetupToolingForLLVM.html</a></p> <!-- ======================================================================= --> <h2 id="intro">Introduction</h2> <!-- ======================================================================= --> <p>Tools built with LibTooling, like Clang Plugins, run <code>FrontendActions</code> over code. <!-- See FIXME for a tutorial on how to write FrontendActions. --> In this tutorial, we'll demonstrate the different ways of running clang's <code>SyntaxOnlyAction</code>, which runs a quick syntax check, over a bunch of code.</p> <!-- ======================================================================= --> <h2 id="runoncode">Parsing a code snippet in memory.</h2> <!-- ======================================================================= --> <p>If you ever wanted to run a <code>FrontendAction</code> over some sample code, for example to unit test parts of the Clang AST, <code>runToolOnCode</code> is what you looked for. Let me give you an example: <pre> #include "clang/Tooling/Tooling.h" TEST(runToolOnCode, CanSyntaxCheckCode) { // runToolOnCode returns whether the action was correctly run over the // given code. EXPECT_TRUE(runToolOnCode(new clang::SyntaxOnlyAction, "class X {};")); } </pre> <!-- ======================================================================= --> <h2 id="standalonetool">Writing a standalone tool.</h2> <!-- ======================================================================= --> <p>Once you unit tested your <code>FrontendAction</code> to the point where it cannot possibly break, it's time to create a standalone tool. For a standalone tool to run clang, it first needs to figure out what command line arguments to use for a specified file. To that end we create a <code>CompilationDatabase</code>. There are different ways to create a compilation database, and we need to support all of them depending on command-line options. There's the <code>CommonOptionsParser</code> class that takes the responsibility to parse command-line parameters related to compilation databases and inputs, so that all tools share the implementation. </p> <h3 id="parsingcommonoptions">Parsing common tools options.</h3> <p><code>CompilationDatabase</code> can be read from a build directory or the command line. Using <code>CommonOptionsParser</code> allows for explicit specification of a compile command line, specification of build path using the <code>-p</code> command-line option, and automatic location of the compilation database using source files paths. <pre> #include "clang/Tooling/CommonOptionsParser.h" using namespace clang::tooling; int main(int argc, const char **argv) { // CommonOptionsParser constructor will parse arguments and create a // CompilationDatabase. In case of error it will terminate the program. CommonOptionsParser OptionsParser(argc, argv); // Use OptionsParser.GetCompilations() and OptionsParser.GetSourcePathList() // to retrieve CompilationDatabase and the list of input file paths. } </pre> </p> <h3 id="tool">Creating and running a ClangTool.</h3> <p>Once we have a <code>CompilationDatabase</code>, we can create a <code>ClangTool</code> and run our <code>FrontendAction</code> over some code. For example, to run the <code>SyntaxOnlyAction</code> over the files "a.cc" and "b.cc" one would write: <pre> // A clang tool can run over a number of sources in the same process... std::vector<std::string> Sources; Sources.push_back("a.cc"); Sources.push_back("b.cc"); // We hand the CompilationDatabase we created and the sources to run over into // the tool constructor. ClangTool Tool(OptionsParser.GetCompilations(), Sources); // The ClangTool needs a new FrontendAction for each translation unit we run // on. Thus, it takes a FrontendActionFactory as parameter. To create a // FrontendActionFactory from a given FrontendAction type, we call // newFrontendActionFactory<clang::SyntaxOnlyAction>(). int result = Tool.run(newFrontendActionFactory<clang::SyntaxOnlyAction>()); </pre> </p> <h3 id="main">Putting it together - the first tool.</h3> <p>Now we combine the two previous steps into our first real tool. This example tool is also checked into the clang tree at tools/clang-check/ClangCheck.cpp. <pre> // Declares clang::SyntaxOnlyAction. #include "clang/Frontend/FrontendActions.h" #include "clang/Tooling/CommonOptionsParser.h" #include "clang/Tooling/Tooling.h" // Declares llvm::cl::extrahelp. #include "llvm/Support/CommandLine.h" using namespace clang::tooling; using namespace llvm; // CommonOptionsParser declares HelpMessage with a description of the common // command-line options related to the compilation database and input files. // It's nice to have this help message in all tools. static cl::extrahelp CommonHelp(CommonOptionsParser::HelpMessage); // A help message for this specific tool can be added afterwards. static cl::extrahelp MoreHelp("\nMore help text..."); int main(int argc, const char **argv) { CommonOptionsParser OptionsParser(argc, argv); ClangTool Tool(OptionsParser.GetCompilations(), OptionsParser.GetSourcePathList()); return Tool.run(newFrontendActionFactory<clang::SyntaxOnlyAction>()); } </pre> </p> <h3 id="running">Running the tool on some code.</h3> <p>When you check out and build clang, clang-check is already built and available to you in bin/clang-check inside your build directory.</p> <p>You can run clang-check on a file in the llvm repository by specifying all the needed parameters after a "--" separator: <pre> $ cd /path/to/source/llvm $ export BD=/path/to/build/llvm $ $BD/bin/clang-check tools/clang/tools/clang-check/ClangCheck.cpp -- \ clang++ -D__STDC_CONSTANT_MACROS -D__STDC_LIMIT_MACROS \ -Itools/clang/include -I$BD/include -Iinclude -Itools/clang/lib/Headers -c </pre> </p> <p>As an alternative, you can also configure cmake to output a compile command database into its build directory: <pre> # Alternatively to calling cmake, use ccmake, toggle to advanced mode and # set the parameter CMAKE_EXPORT_COMPILE_COMMANDS from the UI. $ cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON . </pre> </p> <p> This creates a file called compile_commands.json in the build directory. Now you can run clang-check over files in the project by specifying the build path as first argument and some source files as further positional arguments: <pre> $ cd /path/to/source/llvm $ export BD=/path/to/build/llvm $ $BD/bin/clang-check -p $BD tools/clang/tools/clang-check/ClangCheck.cpp </pre> </p> <h3 id="builtin">Builtin includes.</h3> <p>Clang tools need their builtin headers and search for them the same way clang does. Thus, the default location to look for builtin headers is in a path $(dirname /path/to/tool)/../lib/clang/3.2/include relative to the tool binary. This works out-of-the-box for tools running from llvm's toplevel binary directory after building clang-headers, or if the tool is running from the binary directory of a clang install next to the clang binary.</p> <p>Tips: if your tool fails to find stddef.h or similar headers, call the tool with -v and look at the search paths it looks through.</p> <h3 id="linking">Linking.</h3> <p>Please note that this presents the linking requirements at the time of this writing. For the most up-to-date information, look at one of the tools' Makefiles (for example <a href="http://llvm.org/viewvc/llvm-project/cfe/trunk/tools/clang-check/Makefile?view=markup">clang-check/Makefile</a>). </p> <p>To link a binary using the tooling infrastructure, link in the following libraries: <ul> <li>Tooling</li> <li>Frontend</li> <li>Driver</li> <li>Serialization</li> <li>Parse</li> <li>Sema</li> <li>Analysis</li> <li>Edit</li> <li>AST</li> <li>Lex</li> <li>Basic</li> </ul> </p> </div> </body> </html>