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OCLint.6.RecursiveASTVisitor-class-from-clangAST-library

开发技术 开发技术 2022-07-18 次浏览

RecursiveASTVisitor class from clangAST library

 

1. What's RecursiveASTVisitor?

RecursiveASTVisitor class is defined at the file ${LLVM_PROJECT_PATH}/clang/include/clang/AST/RecursiveASTVisitor.h.

 

 

2. Macros in RecursiveASTVisitor

There are many macros in the RecursiveASTVisitor.h file:

StmtNodes.inc, TypeNodes.inc, TypeLocNodes.def, DeclNodes.inc, OMP.inc, AttrVisitor.inc

 

2.1 TRAVERSE_STMT_BASE(NAME, CLASS, VAR, QUEUE)

If this class(RecursiveASTVisitor) and Derived class have the same "Traverse##NAME" function, then

convert '*this' into Derived type and call "Traverse##NAME" function with 'VAR' and 'QUEUE'.

If not, convert '*this' into Derived type and call "Traverse##NAME" function with 'VAR'.

 

 1   // Traverse the given statement. If the most-derived traverse function takes a
 2   // data recursion queue, pass it on; otherwise, discard it. Note that the
 3   // first branch of this conditional must compile whether or not the derived
 4   // class can take a queue, so if we're taking the second arm, make the first
 5   // arm call our function rather than the derived class version.
 6 #define TRAVERSE_STMT_BASE(NAME, CLASS, VAR, QUEUE)                            
 7   (::clang::detail::has_same_member_pointer_type<                              
 8        decltype(&RecursiveASTVisitor::Traverse##NAME),                         
 9        decltype(&Derived::Traverse##NAME)>::value                              
10        ? static_cast<std::conditional_t<                                       
11              ::clang::detail::has_same_member_pointer_type<                    
12                  decltype(&RecursiveASTVisitor::Traverse##NAME),               
13                  decltype(&Derived::Traverse##NAME)>::value,                   
14              Derived &, RecursiveASTVisitor &>>(*this)                         
15              .Traverse##NAME(static_cast<CLASS *>(VAR), QUEUE)                 
16        : getDerived().Traverse##NAME(static_cast<CLASS *>(VAR)))

 

2.2 STMT(CLASS, PARENT) and StmtNodes.inc

Using the StmtNodes.inc file and STMT() macro define the Traverse##CLASS() function.

 

2.2.1 CLASS

The 'CLASS' would be any statement: BreakStmt, CXXCatchStmt, CXXForRangeStmt, CXXTryStmt,

CapturedStmt, CompoundStmt, ContinueStmt, CoroutineBodyStmt, DeclStmt, DoStmt, ForStmt,

GotoStmt, IfStmt, IndirectGotoStmt, MSDependentExistsStmt, NullStmt, ObjCAtCatchStmt, ObjCAtFinallyStmt,

ObjCAtSynchronizedStmt, ObjCAtThrowStmt, ObjCAtTryStmt, ObjCAutoreleasePoolStmt, 

ObjCForCollectionStmt, ReturnStmt, CaseStmt, DefaultStmt, AttributedStmt, LabelStmt, WhileStmt, ... ... 

 
1 // Declare Traverse*() for all concrete Stmt classes.
2 #define ABSTRACT_STMT(STMT)
3 #define STMT(CLASS, PARENT) 
4   bool Traverse##CLASS(CLASS *S, DataRecursionQueue *Queue = nullptr);
5 #include "clang/AST/StmtNodes.inc"

 

2.3  Define the WalkUpFrom##Class() and Visit##CLASS() functions

 

By defining the WalkUpFrom##CLASS() and Visit##CLASS() functions to provide the defualt implementations for 

RecursiveASTVisitor class. The values of 'CLASS' are the same as "2.2.1 CLASS".

 

 1   // Define WalkUpFrom*() and empty Visit*() for all Stmt classes.
 2   bool WalkUpFromStmt(Stmt *S) { return getDerived().VisitStmt(S); }
 3   bool VisitStmt(Stmt *S) { return true; }
 4 #define STMT(CLASS, PARENT)                                                    
 5   bool WalkUpFrom##CLASS(CLASS *S) {                                           
 6     TRY_TO(WalkUpFrom##PARENT(S));                                             
 7     TRY_TO(Visit##CLASS(S));                                                   
 8     return true;                                                               
 9   }                                                                            
10   bool Visit##CLASS(CLASS *S) { return true; }
11 #include "clang/AST/StmtNodes.inc"

 

 

3. Traversal

 

3.1 Type Traversal

 

 

3.2 TypeLoc Traversal

 

 

 

3.3 Decl Traversal

 

 

3.4 Stmt Traversal

 

 

4. Preprocessing this file

The file contains a lot of macros, we will preprocess this file to get the preprocessed file.

// LLVM_PROJECT_PATH is the root path of llvm project.
//
// Using `export LLVM_PROJECT_PATH = ` to declare this env.
clang --trace-includes -D__cplusplus=201402L
-I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/
-I${LLVM_PROJECT_PATH}/clang/include/
-I${LLVM_PROJECT_PATH}/.build_RelWithDebInfo/tools/clang/include/
-I${LLVM_PROJECT_PATH}/.build_RelWithDebInfo/include/
-I${LLVM_PROJECT_PATH}/llvm/include/
-E RecursiveASTVisitor.h -o tmp.ii

 

4.1 Delete the Blank Line

  1. Open your code in Visual Studio Code.
  2. From Edit Menu, select Replace or use a short cut key ( command + Option + F on Mac or Ctrl + H on Windows)
  3. In the find box type ^(s)*$n.
  4. Leave the replace box empty.
  5. Make sure the 'Use Regular Expression' is selected.
  6. Select the 'Replace All' button.

4.2 Delete the Linemarker  

The linemarker line is like the following:

# 163 "/LLVM/llvm-project/.build_RelWithDebInfo/tools/clang/include/clang/AST/DeclNodes.inc"

 

To delete the linemarker, as the "4.1 Delete the Blank Line" section, we replace the regex in step 3 with "^#(.)+$n". 

 

4.3 Delete the header files

Delete the codes from including header files.

 

The result of preprocessing RecursiveASTVisitor.h using clang -E is at https://gist.github.com/vitonzhangtt/8a1434c22d956bad8cd52259fc7044b0.

 

 

 

 

 

 

 


Reference

1. clang::RecursiveASTVisitor< Derived > Class Template Reference

A class that does preorder or postorder depth-first traversal on the entire Clang AST and visits each node.

https://clang.llvm.org/doxygen/classclang_1_1RecursiveASTVisitor.html

 

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