[Bug libstdc++/70530] [DR2468] You should probably add addressof (a) != addressof (b) check to std::swap

[safinaskar at mail dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70530

Askar Safin <safinaskar at mail dot ru> changed:

           What    |Removed                     |Added
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             Status|RESOLVED                    |REOPENED
         Resolution|INVALID                     |---

--- Comment #5 from Askar Safin <safinaskar at mail dot ru> ---
I will try to repeat.

1. DR 2468 says that after "a = std::move (a)" state of a is unspecified
2. libstdc++'s current std::swap is just 3 moves without any checks
3. From 1 and 2 current libstdc++'s std::swap (a, a) leave a in unspecified
state
4. But (as it seems for me) the standard nowhere says that std::swap (a, a) is
unspecified. So, it should be specified
5. Moreover, you just said "self-swap is not undefined", i. e. "self-swap is
defined" (I assume there is no typo here). This acknowledges 4.

So, we see clear contradiction between 3 and 4. So, something should be fixed.
Either libstdc++, either c++ standard. One solution is to fix libstdc++'s
std::swap. Other is to write to standard that std::swap (a, a) is unspecified.
There may be other solutions.

I reopen this bug