From: Philip Pronin <philipp@fb.com>
Date: Fri, 2 Sep 2016 16:51:19 +0000 (-0700)
Subject: delete const rvalue reference ctor of folly::Function
X-Git-Tag: v2016.09.05.00
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=1813ca3f3ec3cd72b6a938d2d561fe71ad5a76a7;p=folly.git

delete const rvalue reference ctor of folly::Function

Summary:
This code compiles and is causing stack overflow at runtime:

```
using F = folly::Function<void()>;
void foo(F);

F bar;
auto baz = [bar = std::move(bar)] {
  foo(std::move(bar));
};
baz();
```

The bug there is that `baz` is missing `mutable` keyword, so when
constructing argument for `foo`, `F(const F&&)` is called, which is selecting
`template <typename Fun> F(Fun&&)` (where `Fun = F const`) and we end up in
an infinite `F<Fun>(Fun&&) <-> F<Fun>(Fun&&, SmallTag|HeapTag)` cycle.

This diff transforms this easy-to-make-bug into compile-time error.

Reviewed By: yfeldblum

Differential Revision: D3810269

fbshipit-source-id: f80a18ab02bd0715d692cf67c3c8943f557c2982
---

diff --git a/folly/Function.h b/folly/Function.h
index 570f5b8e..91a8c6a1 100644
--- a/folly/Function.h
+++ b/folly/Function.h
@@ -466,6 +466,7 @@ class Function final : private detail::function::FunctionTraits<FunctionType> {
   // (i.e., `template <typename Fun> Function(Fun&&)`).
   Function(Function&) = delete;
   Function(const Function&) = delete;
+  Function(const Function&&) = delete;
 
   /**
    * Move constructor