forked from OSchip/llvm-project
5179eb7821
Replace inheriting constructors implementation with new approach, voted into C++ last year as a DR against C++11. Instead of synthesizing a set of derived class constructors for each inherited base class constructor, we make the constructors of the base class visible to constructor lookup in the derived class, using the normal rules for using-declarations. For constructors, UsingShadowDecl now has a ConstructorUsingShadowDecl derived class that tracks the requisite additional information. We create shadow constructors (not found by name lookup) in the derived class to model the actual initialization, and have a new expression node, CXXInheritedCtorInitExpr, to model the initialization of a base class from such a constructor. (This initialization is special because it performs real perfect forwarding of arguments.) In cases where argument forwarding is not possible (for inalloca calls, variadic calls, and calls with callee parameter cleanup), the shadow inheriting constructor is not emitted and instead we directly emit the initialization code into the caller of the inherited constructor. Note that this new model is not perfectly compatible with the old model in some corner cases. In particular: * if B inherits a private constructor from A, and C uses that constructor to construct a B, then we previously required that A befriends B and B befriends C, but the new rules require A to befriend C directly, and * if a derived class has its own constructors (and so its implicit default constructor is suppressed), it may still inherit a default constructor from a base class llvm-svn: 274049 |
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