an unofficial, non-gentle introduction to clang compiler.

1. Clang:
A New Tool for Old Languages
MORITA Hajime <omo@dodgson.org>
http://steps.dodgson.org/
2009/03/21
1

2. //===----------------------------------------------------------------------===//
// C Language Family Front-end
//===----------------------------------------------------------------------===//
Chris Lattner
I. Introduction:
clang: noun
1. A loud, resonant, metallic sound.
2. The strident call of a crane or goose.
3. C-language family front-end toolkit.
http://llvm.org/svn/llvm-project/cfe/trunk/README.txt

3. • Clang ?
• ?
3

4. • Clang ?
• ?
4

5. //===----------------------------------------------------------------------===//
// C Language Family Front-end
//===----------------------------------------------------------------------===//
Chris Lattner
I. Introduction:
clang: noun
1. A loud, resonant, metallic sound.
2. The strident call of a crane or goose.
3. C-language family front-end toolkit.
http://llvm.org/svn/llvm-project/cfe/trunk/README.txt

6. //===----------------------------------------------------------------------===//
// C Language Family Front-end
//===----------------------------------------------------------------------===//
Chris Lattner
I. Introduction:
clang: noun
1. A loud, resonant, metallic sound.
2. The strident call of a crane or goose.
3. C-language family front-end toolkit.
http://llvm.org/svn/llvm-project/cfe/trunk/README.txt

7. C/C++/Obj-C
• LLVM.org
• 2006
• written in C++
6

8. C/C++/Obj-C
• LLVM
• Apple
• (as LLVM)
• (as LLVM)
7

9. LLVM
•
•
•
• JIT
8

10. Apple
•
• gcc ( )
• MSVC ( )
•
9

11. •
•
•
• AST
•
• 10

12. Frontend
Lex
Driver
Basic Parse
CodeGen
LLVM/
Sema LLVM
System
Analysis
AST
Rewrite
Core App
11

13. Core 1/5:
clang/Basic
• I/O (+ )
•
•
•
• basic LLVM
12

14. Core 2/5: Token
clang/Lex Preprocessor
Preprocessor
Lexer
• Lexer, Token, Preprocessor, ...
• Lexer: Lexer PTHLexer
• pull style: Lexer::Lex(Token& result);
• hand-written
• (: )
• PTH(Preprocessed-Token-Header)
13

15. Core 3/5:
clang/Parse
Token
• Parser, Action, ....
• Parser: Preprocessor Parser Action
• push-style
• C/C++/Obj-C (!)
14

16. Core 4/5:
clang/Sema
Parser Action
• ParseAST(Preprocessor &PP, AST
ASTConsumer *Consumer, Consumer
TranslationUnit *TU,
Sema
bool PrintStats);
Translation
• Sema : public Action Unit
• callback+Token→AST
15

17. Core 5/5:
Translation AST
Unit Context
clang/AST Type Decl Expr
• Decl :
• VarDecl, FunctionDecl, CXXRecordDecl, ...
• Type :
• QualType, BuiltinType, ComplexType, ...
• Expr :
• DeclRefExpr, IntegerLiteral, UnaryOperator, ...
16

18. Decl
Type
NamedDecl
QualType
DeclContext ValueDecl
ParmVar
Decl
FunctionDecl
Stmt Expr
CXX
MethodDecl CXX
RecordDecl
17

19. App libraries
• Analysis:
•
• Rewrite:
• (Rope, DeltaTree)
• Obj-C → C
• HTML
• AST
18

20. • Clang ?
• ?
19

21. •
( )
•
( )
20

22. •
OK: Driver/clang.cpp
•
• ASTConsumer
• DiagnosticClient
•
21

23. : main()
:
- #include-s
-
22

24. #include-s:
#include <vector>
#include <string>
#include <iosfwd>
#include <llvm/Support/raw_ostream.h>
#include <clang/Frontend/CompileOptions.h>
#include <clang/Frontend/PathDiagnosticClients.h>
#include <clang/Frontend/InitHeaderSearch.h>
#include <clang/Frontend/TextDiagnosticBuffer.h>
#include <clang/Frontend/TextDiagnosticPrinter.h>
#include <clang/Analysis/PathDiagnostic.h>
#include <clang/AST/Decl.h>
#include <clang/AST/DeclCXX.h>
#include <clang/AST/TranslationUnit.h>
#include <clang/CodeGen/ModuleBuilder.h>
#include <clang/Sema/ParseAST.h>
#include <clang/Sema/SemaDiagnostic.h>
#include <clang/AST/ASTConsumer.h>
#include <clang/Parse/Parser.h>
#include <clang/Lex/HeaderSearch.h>
#include <clang/Lex/LexDiagnostic.h>
#include <clang/Basic/FileManager.h>
•
#include <clang/Basic/SourceManager.h>
#include <clang/Basic/TargetInfo.h>
#include <clang/Basic/Diagnostic.h>
#include <llvm/ADT/OwningPtr.h>
#include <llvm/ADT/SmallPtrSet.h>
#include <llvm/ADT/StringExtras.h>
#include <llvm/Config/config.h>
#include <llvm/Support/CommandLine.h>
#include <llvm/Support/ManagedStatic.h>
#include <llvm/Support/MemoryBuffer.h>
#include <llvm/Support/PluginLoader.h>
#include <llvm/Support/PrettyStackTrace.h>
#include <llvm/Support/Timer.h>
#include <llvm/System/Host.h>
#include <llvm/System/Path.h>
#include <llvm/System/Signals.h>
#include <iostream>
23

25. : ASTConsumer
• Driver/ASTConsumers.cpp
• ASTDumper:
• DeclContextPrinter: ( )
• :
↑
24

26. class DeclContextPrinter : public ASTConsumer {
llvm::raw_ostream& Out;
public:
DeclContextPrinter() : Out(llvm::errs()) {}
void HandleTranslationUnit(TranslationUnit& TU) {
TranslationUnitDecl* TUD =
TU.getContext().getTranslationUnitDecl();
PrintDeclContext(TUD, 4);
}
void PrintDeclContext(const DeclContext* DC, unsigned Indentation)
};
25

27. void DeclContextPrinter::PrintDeclContext(const DeclContext* DC,
unsigned Indentation) {
// Print DeclContext name.
switch (DC->getDeclKind()) {
case Decl::TranslationUnit:
Out << quot;[translation unit] quot; << DC;
break;
case Decl::Namespace: {
Out << quot;[namespace] quot;;
const NamespaceDecl* ND = cast<NamespaceDecl>(DC);
Out << ND->getNameAsString();
break;
}
...
case Decl::CXXRecord: {
const CXXRecordDecl* RD = cast<CXXRecordDecl>(DC);
if (RD->isDefinition())
Out << quot;[class] quot;;
else
Out << quot;<class> quot;;
Out << RD->getNameAsString() << quot; quot; << DC;
break;
}
...
26

28. AST
• /
(better doxygen, GLOBAL, LXR, ...)
•
(better/worse RPC, Serializer, SWIG, ...)
• ,
AST
• AOP ( , , ....)
•
http://people.imendio.com/richard/gtk-rewriter/
27

29. • ( FS)
• ( )
• (Lexer )
• C++
• ...
28

30. 5 C/Objc-C/C++
•
• +
• ?
• (ry
29

31. Clang
• C++ C++ !!!
• !!!
• Apple!!!
• !!!
30

32. For more:
• http://clang.llvm.org/get_started.html
• http://llvm.org/devmtg/2008-08/Naroff_Clang.pdf
• trunk/Driver/
clang
• http://www.flickr.com/photos/darrenhunter/2918246464/
31