junaire added a comment. Frankly speaking, this is really a randomly written patch, and I have never thought it would raise so much concern. But I believe I can handle it if you guys can give me some trust and little guidance! <3
In D119609#3355409 <https://reviews.llvm.org/D119609#3355409>, @aaron.ballman wrote: > Thank you for looking into this! I'm not certain this is the correct > approach, however. The comment on the function is: > > /// ActOnCapScopeReturnStmt - Utility routine to type-check return > statements > /// for capturing scopes. > > however, there's not a capture scope in the test case -- the GNU expression > statement is within the parameter list, which can't capture anything: > https://godbolt.org/z/3KrEx8hEW. I think the issue might be whatever causes > us to call `ActOnCapScopeReturnStmt()` in the first place. Yes, you're correct. From the call stack we can see: clang::Sema::ActOnCapScopeReturnStmt clang::Sema::BuildReturnStmt // bad things happened here :( clang::Sema::ActOnReturnStmt clang::Parser::ParseStatementOrDeclarationAfterAttributes clang::Parser::ParseStatementOrDeclaration clang::Parser::ParseCompoundStatementBody clang::Parser::ParseCompoundStatement clang::Parser::ParseParenExpression clang::Parser::ParseCastExpression clang::Parser::ParseCastExpression clang::Parser::ParseAssignmentExpression clang::Parser::ParseParameterDeclarationClause clang::Parser::ParseLambdaExpressionAfterIntroducer When clang is parsing a lambda and hit a `ReturnStmt`, it will do something like: if (isa<CapturingScopeInfo>(getCurFunction())) return ActOnCapScopeReturnStmt(ReturnLoc, RetValExp, NRInfo, SupressSimplerImplicitMoves); However, in this case, though what `getCurFunction()` returns is a `CapturingScopeInfo`, we're not finished building the lambda! so clang will crash when we try to use its `CallOperator`: bool HasDeducedReturnType = CurLambda && hasDeducedReturnType(CurLambda->CallOperator); So my original patch is to add an extra check when we decide to jump into `ActOnCapScopeReturnStmt`, however, I can't pass all the tests. Then I discovered that `CurLambda` can be `nullptr`, and we still need to call `ActOnCapScopeReurnStmt`, so I changed my patch. I'm not really sure why this would happen, maybe I need to dig into the code more. > But there's a design question there as to whether expression statements in a > lambda default parameter value makes sense *at all*, because the lambda is an > object that can be passed around to others to call. e.g., > https://godbolt.org/z/3Edeqv9qv Not sure about this, but at least gcc accepts code below: void g() { auto whatever = [=](int foo = ({ return;5; })) {}; } I agree to listen to what gcc folks think about it. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D119609/new/ https://reviews.llvm.org/D119609 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
