[llvm-commits] [PATCH] New compatibility macro: LLVM_LVALUE_FUNCTION

[Jordan Rose]

Hi, all. I'm a committer up on the Clang side, but lately I've been working on an internal side project that gets to use C++11. I was trying to put a non-copyable type in an llvm::Optional, but I discovered that that's a problem when you want to conditionally move it somewhere else.

I'd like to add rvalue overrides to Optional::getValue, but of course you can't do that unless the regular const version is annotated with an ampersand. Does anyone object to adding a new Compiler.h macro that expands to '&' when rvalue references are supported? It would look like this:

const T& getValue() const LLVM_LVALUE_FUNCTION { … }

This isn't perfect, but it could also help alleviate the "returning an inner pointer of a temporary" mistake that we keep making, and which GCC keeps causing us to crash on:

const T *getInteriorPointer() const LLVM_LVALUE_FUNCTION;
#if LLVM_USE_RVALUE_REFERENCES
void getInteriorPointer() && LLVM_DELETED_FUNCTION;
#endif

Thanks,
Jordan

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