[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
diff --git a/clang/lib/AST/StmtProfile.cpp b/clang/lib/AST/StmtProfile.cpp
index 327b4c0..30e094c 100644
--- a/clang/lib/AST/StmtProfile.cpp
+++ b/clang/lib/AST/StmtProfile.cpp
@@ -1258,6 +1258,7 @@
C != CEnd; ++C) {
ID.AddInteger(C->getCaptureKind());
switch (C->getCaptureKind()) {
+ case LCK_StarThis:
case LCK_This:
break;
case LCK_ByRef: