Questions about rationale of ASTMatcher and RecursiveASTVisitor?

[for-just-we]

Hi, author. Thanks for you excellent tutorial, I have some questions about your code in UnusedForLoopVar?

• why ASTMatcher would work? you use API LoopVar->isUsed(true) in line 64 of UnusedForLoopVar.cpp to check whether LoopVar is used? how the attribute used of LoopVar is set to true. Does clang do this when it parse source code into AST?

• you use API RecursiveASTVisitor::TraverseStmt(S->getBody()); instead of this->TraverseStmt(S->getBody()); in line 134 of UnusedForLoopVar.cpp, what's the difference between them.

[banach-space]

Hello 👋🏻 !

Thanks for you excellent tutorial

Thank you for your kind words! :)

why ASTMatcher would work? you use API LoopVar->isUsed(true) in line 64 of UnusedForLoopVar.cpp to check whether LoopVar is used?

The approach with the AST Matcher works for i below (it is not used). It does not work for j (it is used):

for (int j = 0, i = 0; j < 20; j++) { }

Does it make sense?

how the attribute used of LoopVar is set to true. Does clang do this when it parse source code into AST?

Sorry, I don't know, I'm not that familiar with the implementation of Clang.

you use API RecursiveASTVisitor::TraverseStmt(S->getBody()); instead of this->TraverseStmt(S->getBody()); in line 134 of UnusedForLoopVar.cpp, what's the difference between them.

Both approaches should be fine - they will result in a call to TraverseStmt. Good catch :)