[cfe-dev] Question of RecursiveASTVisitor class

[Nikola Smiljanic]

On Tue, Nov 4, 2014 at 7:14 AM, Xiaohui Chen <xchen422 at uwo.ca> wrote:

> Thanks for your reply.
>
> I am confusing here:
>
> 1. Traverse method visits AST nodes that form a tree. CXXRecordDecl is the
> parent of each of its CXXMethodDecls and FieldDecls.
>
>  CXXMethodDecls ( FieldDecls )  is not  a member of CXXRecordDecl and also
> does not inherit from CXXRecordDecl, so how could
> you define them as parent-child relationship?


CXXRecordDecl contains CXXMethodDecls and RecordDecl contains FieldDecls.
They're just stored in the DeclContext class but are exposed with
method_begin/method_end and field_begin/field_end.


> 2. WalkUpFrom method visits the class hierarchy of a single AST node.
> CXXRecordDecl inherits RecordDecl which inherits TagDecl etc.
>
> here TagDecl has three direct parents, so will WalkUpFrom be applied to
> these three classes?
>
>
TagDecl does have three super classes but only one of them is also an AST
node. AST is built from declarations, statements and types. DeclContext
represents a declaration context and structs/classes introduce one. They
are also redeclarable (forward declaration) which is what Redeclarable
class keeps track of.



> sincerely
> xiaohui
>
>
> On 11/03/14, *Nikola Smiljanic * <popizdeh at gmail.com> wrote:
>
> There are two parent-child relationships at play.
>
> 1. Traverse method visits AST nodes that form a tree. CXXRecordDecl is the
> parent of each of its CXXMethodDecls and FieldDecls. This is what you'll
> see with clang -cc1 -ast-dump
> 2. WalkUpFrom method visits the class hierarchy of a single AST node.
> CXXRecordDecl inherits RecordDecl which inherits TagDecl etc. Think of
> serialization, to serialize CXXRecordDecl you'd first want to serialize
> everything from the base class and so on recursively.
>
> On Mon, Nov 3, 2014 at 12:32 PM, Xiaohui Chen <xchen422 at uwo.ca> wrote:
>
>>  Dear all:
>>
>> My name is Xiaohui Chen, a computer science student in UWO in canada and
>> i am using Clang as the frontend of my project, but i am confusing of the
>> following statements.
>> PS: i am a newbie.
>>
>> These tasks are done by three groups of methods, respectively:00089 ///   1. TraverseDecl(Decl *x) does task #1.  It is the entry point00090 ///      for traversing an AST rooted at x.  This method simply00091 ///      dispatches (i.e. forwards) to TraverseFoo(Foo *x) where Foo00092 ///      is the dynamic type of *x, which calls WalkUpFromFoo(x) and00093 ///      then recursively visits the child nodes of x.00094 ///      TraverseStmt(Stmt *x) and TraverseType(QualType x) work00095 ///      similarly.00096 ///   2. WalkUpFromFoo(Foo *x) does task #2.  It does not try to visit00097 ///      any child node of x.  Instead, it first calls WalkUpFromBar(x)00098 ///      where Bar is the direct parent class of Foo (unless Foo has00099 ///      no parent), and then calls VisitFoo(x) (see the next list item).00100 ///   3. VisitFoo(Foo *x) does task #3.00101 ///00102 /// These three method groups are tiered (Traverse* > WalkUpFrom* >00103 /// Visit*).  A method (e.g. Traverse*) may call methods from the same00104 /// tier (e.g. other Traverse*) or one tier lower (e.g. WalkUpFrom*).00105 /// It may not call methods from a higher tier.
>>
>> According to the above statement, the calling relationship between these
>> functions are organized in this way in general:
>>
>> Traversal*()
>> {
>>         .......
>>         WalkUpFrom*();
>>         .......
>> }
>>
>> WalkUpFrom*()
>> {
>>          .......
>>          Visit*();
>>          .......
>>
>> }
>>
>> am i right?
>>
>> For this statement:
>>
>> 00096 ///   2. WalkUpFromFoo(Foo *x) does task #2.  It does not try to visit00097 ///      any child node of x.  Instead, it first calls WalkUpFromBar(x)00098 ///      where Bar is the direct parent class of Foo (unless Foo has00099 ///      no parent), and then calls VisitFoo(x) (see the next list item).
>>
>> what do you mean by saying "the direct parent class of Foo"?
>> why i need to visit the parent class before i visit the current class?
>> what is the purpose? Could you please give me a short example?
>>
>> Thank you in advance!
>>
>> Sincerely
>> xiaohui
>>
>>
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>>
>>
>
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