How could I visit the same AST?

I am learning to visiting ast to collect some information by API of libTooling.

When I process the source file of postfix-3.0.3/src/global/mail_params.c, I met something strange.

When I visit the AST by VisitStmt(), I could find that there would be a sub level of “InitListExpr” in the first level of “InitListExpr” as attachment shown.

However, when I want to visit the parent AST of StringLiteral by VisitStringLiteral(), the sub level of “InitListExpr” is gone, I can only get the higher level “InitListExpr”.

I get the parent AST by using “CompilerInstance.getASTContext().getParents(Stmt*)”.

So, how to visit the same AST in these two methods?

Thank you a lot !