[cfe-dev] RecursiveASTVisitor Behavior

[David Rector via cfe-dev]

> On Mar 18, 2021, at 11:42 AM, Michael Chiu via cfe-dev <cfe-dev at lists.llvm.org> wrote:
> 
> Hi All,
> 
> I have c code, below, that I'm trying to visit the AST of by using RecursiveASTVisitor. I'm trying to get the RecursiveASTVisitor to visit variable declarations (clang::VarDecl) by implementing bool VistVarDecl(clang::VarDecl *vardecl). However, the clang::VarDecl nodes are never visited even though I've managed to visit all the other nodes in the AST though. Moreover, using clang-query on test1.c I can match varDecl.
> 
> Does anyone know the clang::VarDecl nodes are the only nodes that aren't visited by the RecursiveASTVisitor but are matched by clang-query?
> 
> Thanks in advaince!
> 
> ```
> double multiply(double x, double y) {
>     return x * y * y;
> }
> 
> int main(int argc, char const *argv[])
> {
>     double a;
> 
>     int b;
> 
>     float d;
> 
>     double x = 3.0;
>     double y = 5.0;
> 
>     double z = multiply(x,y);
> 
>     return 0;
> }
> ```
> My RecursiveASTVisitor is as follows:
> ```
> struct MyASTVisitor : public clang::RecursiveASTVistor<MyASTVisitor> {
>   bool VistVarDecl(clang::VarDecl *vardecl) {
>      llvm::outs() << "Found a VarDecl";

Add `return true;’ here and in the others.  (Traversal halts after the first false return, and all these are returning false by default.)
>   };
> 
>   bool VisitFunctionDecl(clang::FunctionDecl *decl) {
>      llvm::outs() << "Found a FunctionDecl";
>   };
> 
>   // other functions implemented similarly just to see if it visits properly
>   bool VisitParmVarmDecl(clang::ParmVarDecl *paramvardecl);
>   bool VisitCallExpr(clang::CallExpr *callexpr);
>   bool VisitImplicitCastExpr(clang::ImplicitCastExpr *castexpr);
>   bool VisitBinaryOperator(clang::BinaryOperator *bo);
>   bool VisitDeclStmt(clang::DeclStmt *declstmt);
>   bool VisitDeclRefExpr(clang::DeclRefExpr *declrefexpr);
>   bool VisitFloatingLiteral(clang::FloatingLiteral *floatliteral);
> };
> 
> struct MyASTConsumer : public clang::ASTConsumer {
> 
>   bool HandleTopLevelDecl(clang::DeclGroupRef DR) override {
>     for (clang::DeclGroupRef::iterator b = DR.begin(), e = DR.end(); b != e; ++b) {
>         Visitor.TraverseDecl(*b);
>      }
>      return true;
>   }
> private: 
>   MyASTVisitor Visitor;
> };
> ```
> 
> -- 
> Michael.
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