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