[Bug libstdc++/54388] [4.7/4.8 Regression] std::array.at() const results in undefined behaviour

[fweimer at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54388

--- Comment #10 from Florian Weimer <fweimer at redhat dot com> 2012-08-30 
15:39:21 UTC ---
(In reply to comment #9)
> BTW, we definitely need a comment on  why this particular code is so tricky. 
> 
> // NB: Interesting use of comma operator semantics.
> 
> at the very least...
> 
> ;)

Can the compiler warn about the original (buggy) code?