184 lines
7.0 KiB
HTML
184 lines
7.0 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<title>LibTooling</title>
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<link type="text/css" rel="stylesheet" href="../menu.css">
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<link type="text/css" rel="stylesheet" href="../content.css">
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</head>
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<body>
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<div id="content">
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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 FrontendActions over
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code. <!-- 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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SyntaxOnlyAction, 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 FrontendAction over some sample code, for example
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to unit test parts of the Clang AST, runToolOnCode is what you looked for. Let
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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 FrontendAction to the point where it cannot
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possibly break, it's time to create a standalone tool. For a standalone tool
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to run clang, it first needs to figure out what command line arguments to use
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for a specified file. To that end we create a CompilationDatabase.</p>
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<h3 id="compilationdb">Creating a compilation database.</h3>
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<p>CompilationDatabase provides static factory functions to help with parsing
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compile commands from a build directory or the command line. The following code
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allows for both explicit specification of a compile command line, as well as
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retrieving the compile commands lines from a database.
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<pre>
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int main(int argc, const char **argv) {
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// First, try to create a fixed compile command database from the command line
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// arguments.
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llvm::OwningPtr<CompilationDatabase> Compilations(
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FixedCompilationDatabase::loadFromCommandLine(argc, argv));
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// Next, use normal llvm command line parsing to get the tool specific
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// parameters.
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cl::ParseCommandLineOptions(argc, argv);
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if (!Compilations) {
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// In case the user did not specify the compile command line via positional
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// command line arguments after "--", try to load the compile commands from
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// a database in the specified build directory.
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std::string ErrorMessage;
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Compilations.reset(CompilationDatabase::loadFromDirectory(BuildPath,
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ErrorMessage));
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// If there is still no valid compile command database, we don't know how
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// to run the tool.
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if (!Compilations)
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llvm::report_fatal_error(ErrorMessage);
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}
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...
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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 CompilationDatabase, we can create a ClangTool and run our
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FrontendAction over some code. For example, to run the SyntaxOnlyAction over
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the files "a.cc" and "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(*Compilations, 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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#include "llvm/Support/CommandLine.h"
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#include "clang/Frontend/FrontendActions.h"
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#include "clang/Tooling/CompilationDatabase.h"
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#include "clang/Tooling/Tooling.h"
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using namespace clang::tooling;
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using namespace llvm;
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cl::opt<std::string> BuildPath(
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cl::Positional,
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cl::desc("<build-path>"));
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cl::list<std::string> SourcePaths(
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cl::Positional,
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cl::desc("<source0> [... <sourceN>]"),
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cl::OneOrMore);
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int main(int argc, const char **argv) {
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llvm::OwningPtr<CompilationDatabase> Compilations(
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FixedCompilationDatabase::loadFromCommandLine(argc, argv));
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cl::ParseCommandLineOptions(argc, argv);
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if (!Compilations) {
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std::string ErrorMessage;
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Compilations.reset(CompilationDatabase::loadFromDirectory(BuildPath,
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ErrorMessage));
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if (!Compilations)
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llvm::report_fatal_error(ErrorMessage);
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}
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ClangTool Tool(*Compilations, SourcePaths);
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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 $BD tools/clang/tools/clang-check/ClangCheck.cpp
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</pre>
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</p>
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</div>
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</body>
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</html>
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