From dc6b596ebbd3c594c75fc6c6bc6cb7c14fdcec24 Mon Sep 17 00:00:00 2001 From: Faisal Vali Date: Mon, 21 Mar 2016 09:25:37 +0000 Subject: [Cxx1z] Implement Lambda Capture of *this by Value as [=,*this] (P0018R3) Implement lambda capture of *this by copy. For e.g.: struct A { int d = 10; auto foo() { return [*this] (auto a) mutable { d+=a; return d; }; } }; auto L = A{}.foo(); // A{}'s lifetime is gone. // Below is still ok, because *this was captured by value. assert(L(10) == 20); assert(L(100) == 120); If the capture was implicit, or [this] (i.e. *this was captured by reference), this code would be otherwise undefined. Implementation Strategy: - amend the parser to accept *this in the lambda introducer - add a new king of capture LCK_StarThis - teach Sema::CheckCXXThisCapture to handle by copy captures of the enclosing object (i.e. *this) - when CheckCXXThisCapture does capture by copy, the corresponding initializer expression for the closure's data member direct-initializes it thus making a copy of '*this'. - in codegen, when assigning to CXXThisValue, if *this was captured by copy, make sure it points to the corresponding field member, and not, unlike when captured by reference, what the field member points to. - mark feature as implemented in svn Much gratitude to Richard Smith for his carefully illuminating reviews! llvm-svn: 263921 --- clang/lib/Sema/TreeTransform.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'clang/lib/Sema/TreeTransform.h') diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h index fc201292146..7ed52ebb12a 100644 --- a/clang/lib/Sema/TreeTransform.h +++ b/clang/lib/Sema/TreeTransform.h @@ -10089,7 +10089,9 @@ TreeTransform::TransformLambdaExpr(LambdaExpr *E) { // Capturing 'this' is trivial. if (C->capturesThis()) { - getSema().CheckCXXThisCapture(C->getLocation(), C->isExplicit()); + getSema().CheckCXXThisCapture(C->getLocation(), C->isExplicit(), + /*BuildAndDiagnose*/ true, nullptr, + C->getCaptureKind() == LCK_StarThis); continue; } // Captured expression will be recaptured during captured variables -- cgit v1.2.3