Касьянычев М.П. 381806-1 #50
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| void run(const MatchFinder::MatchResult &Result) override { | ||
| // Your code goes here | ||
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| const auto *Item = Result.Nodes.getNodeAs<CStyleCastExpr>("cast"); |
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What if Item is a null pointer? How to protect the program from crashing in such cases?
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Необходимо добавить проверку, что Item не пуст.
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What do you mean by emptiness?
| CastCallBack(Rewriter& rewriter) { | ||
| // Your code goes here | ||
| }; | ||
| CastCallBack(Rewriter& rewriter) : rewriter_(rewriter) { }; |
| Item->getSubExprAsWritten()->getBeginLoc()); | ||
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| StringRef DestTypeString = | ||
| Lexer::getSourceText(CharSourceRange::getTokenRange(Item->getLParenLoc().getLocWithOffset(1), |
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Please describe what the getSourceText() function does.
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Формирует строку для источника в диапазоне CharSourceRange.
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In the range getTokenRange(res->getLParenLoc().getLocWithOffset(1), res->getRParenLoc().getLocWithOffset(-1))
| Result.Context->getLangOpts()); | ||
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| std::string str = ("static_cast<" + DestTypeString + ">").str(); | ||
| const Expr *SubExpr = Item->getSubExprAsWritten()->IgnoreImpCasts(); |
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Please describe the reason for using IgnoreImpCasts() here. What would be the difference if we didn't use this method.
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IgnoreImpCasts() предназначен для игнорирования всех неявных приведений типов. Но в нашей задаче таких приведений нет, следовательно, даже если не использовать этот метод, разницы не будет.
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If you try to print the AST of the test.cpp example, you will see that you have several ImplicitCastExpr nodes:
Depending on which approaches you use to get the subexpression node, you will get different result nodes for the test.cpp example:
Code:
// getSubExpr() retrieves the first cast subexpression
llvm::outs() << "getSubExpr(): " << castNode->getSubExpr()->getStmtClassName();
// getSubExprAsWritten() retrieves the cast subexpression as it was written in the source
// code, looking through any implicit casts or other intermediate nodes
// introduced by semantic analysis.
llvm::outs() << "getSubExprAsWritten(): " << castNode->getSubExprAsWritten()->getStmtClassName();
// getSubExpr() retrieves the first cast subexpression.
// ignoreImpCasts() skips past any implicit casts which might surround this expression until
// reaching a fixed point. It skips the following AST nodes: ImplicitCastExpr, FullExpr.
llvm::outs() << "getSubExpr()->ignoreImpCasts(): " << castNode->getSubExpr()->IgnoreImpCasts()->getStmtClassName();Output:
getSubExpr(): ImplicitCastExpr
getSubExprAsWritten(): DeclRefExpr
getSubExpr()->ignoreImpCasts(): DeclRefExpr
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