docs/LibTooling.html - platform/external/clang - Git at Google

 <!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>
 <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>

 <!-- ======================================================================= -->
 <h2 id="intro">Introduction</h2>
 <!-- ======================================================================= -->

 <p>Tools built with LibTooling, like Clang Plugins, run FrontendActions 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
 SyntaxOnlyAction, 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 FrontendAction over some sample code, for example
 to unit test parts of the Clang AST, runToolOnCode 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 FrontendAction 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 CompilationDatabase.</p>

 <h3 id="compilationdb">Creating a compilation database.</h3>
 <p>CompilationDatabase provides static factory functions to help with parsing
 compile commands from a build directory or the command line. The following code
 allows for both explicit specification of a compile command line, as well as
 retrieving the compile commands lines from a database.
 <pre>
 int main(int argc, const char **argv) {
   // First, try to create a fixed compile command database from the command line
   // arguments.
   llvm::OwningPtr&lt;CompilationDatabase> Compilations(
     FixedCompilationDatabase::loadFromCommandLine(argc, argv));

   // Next, use normal llvm command line parsing to get the tool specific
   // parameters.
   cl::ParseCommandLineOptions(argc, argv);

   if (!Compilations) {
     // In case the user did not specify the compile command line via positional
     // command line arguments after "--", try to load the compile commands from
     // a database in the specified build directory.
     std::string ErrorMessage;
     Compilations.reset(CompilationDatabase::loadFromDirectory(BuildPath,
                                                               ErrorMessage));

     // If there is still no valid compile command database, we don't know how
     // to run the tool.
     if (!Compilations)
       llvm::report_fatal_error(ErrorMessage);
   }
 ...
 }
 </pre>
 </p>

 <h3 id="tool">Creating and running a ClangTool.</h3>
 <p>Once we have a CompilationDatabase, we can create a ClangTool and run our
 FrontendAction over some code. For example, to run the SyntaxOnlyAction 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&lt;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(*Compilations, 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&lt;clang::SyntaxOnlyAction>().
   int result = Tool.run(newFrontendActionFactory&lt;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>
   #include "llvm/Support/CommandLine.h"
   #include "clang/Frontend/FrontendActions.h"
   #include "clang/Tooling/CompilationDatabase.h"
   #include "clang/Tooling/Tooling.h"

   using namespace clang::tooling;
   using namespace llvm;

   cl::opt&lt;std::string> BuildPath(
     cl::Positional,
     cl::desc("&lt;build-path>"));

   cl::list&lt;std::string> SourcePaths(
     cl::Positional,
     cl::desc("&lt;source0> [... &lt;sourceN>]"),
     cl::OneOrMore);

   int main(int argc, const char **argv) {
     llvm::OwningPtr&lt;CompilationDatabase> Compilations(
       FixedCompilationDatabase::loadFromCommandLine(argc, argv));
     cl::ParseCommandLineOptions(argc, argv);
     if (!Compilations) {
       std::string ErrorMessage;
       Compilations.reset(CompilationDatabase::loadFromDirectory(BuildPath,
                                                                 ErrorMessage));
       if (!Compilations)
         llvm::report_fatal_error(ErrorMessage);
     }
     ClangTool Tool(*Compilations, SourcePaths);
     return Tool.run(newFrontendActionFactory&lt;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 $BD tools/clang/tools/clang-check/ClangCheck.cpp
 </pre>
 </p>

 </div>
 </body>
 </html>
	<!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>
	<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>

	<!-- ======================================================================= -->
	<h2 id="intro">Introduction</h2>
	<!-- ======================================================================= -->

	<p>Tools built with LibTooling, like Clang Plugins, run FrontendActions 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
	SyntaxOnlyAction, 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 FrontendAction over some sample code, for example
	to unit test parts of the Clang AST, runToolOnCode 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 FrontendAction 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 CompilationDatabase.</p>

	<h3 id="compilationdb">Creating a compilation database.</h3>
	<p>CompilationDatabase provides static factory functions to help with parsing
	compile commands from a build directory or the command line. The following code
	allows for both explicit specification of a compile command line, as well as
	retrieving the compile commands lines from a database.
	<pre>
	int main(int argc, const char **argv) {
	// First, try to create a fixed compile command database from the command line
	// arguments.
	llvm::OwningPtr<CompilationDatabase> Compilations(
	FixedCompilationDatabase::loadFromCommandLine(argc, argv));

	// Next, use normal llvm command line parsing to get the tool specific
	// parameters.
	cl::ParseCommandLineOptions(argc, argv);

	if (!Compilations) {
	// In case the user did not specify the compile command line via positional
	// command line arguments after "--", try to load the compile commands from
	// a database in the specified build directory.
	std::string ErrorMessage;
	Compilations.reset(CompilationDatabase::loadFromDirectory(BuildPath,
	ErrorMessage));

	// If there is still no valid compile command database, we don't know how
	// to run the tool.
	if (!Compilations)
	llvm::report_fatal_error(ErrorMessage);
	}
	...
	}
	</pre>
	</p>

	<h3 id="tool">Creating and running a ClangTool.</h3>
	<p>Once we have a CompilationDatabase, we can create a ClangTool and run our
	FrontendAction over some code. For example, to run the SyntaxOnlyAction 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(*Compilations, 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>
	#include "llvm/Support/CommandLine.h"
	#include "clang/Frontend/FrontendActions.h"
	#include "clang/Tooling/CompilationDatabase.h"
	#include "clang/Tooling/Tooling.h"

	using namespace clang::tooling;
	using namespace llvm;

	cl::opt<std::string> BuildPath(
	cl::Positional,
	cl::desc("<build-path>"));

	cl::list<std::string> SourcePaths(
	cl::Positional,
	cl::desc("<source0> [... <sourceN>]"),
	cl::OneOrMore);

	int main(int argc, const char **argv) {
	llvm::OwningPtr<CompilationDatabase> Compilations(
	FixedCompilationDatabase::loadFromCommandLine(argc, argv));
	cl::ParseCommandLineOptions(argc, argv);
	if (!Compilations) {
	std::string ErrorMessage;
	Compilations.reset(CompilationDatabase::loadFromDirectory(BuildPath,
	ErrorMessage));
	if (!Compilations)
	llvm::report_fatal_error(ErrorMessage);
	}
	ClangTool Tool(*Compilations, SourcePaths);
	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 $BD tools/clang/tools/clang-check/ClangCheck.cpp
	</pre>
	</p>

	</div>
	</body>
	</html>