[llvm] r243996 - Avoid passing nullptr to std::equal.

[Duncan P. N. Exon Smith via llvm-commits]

> On 2015-Aug-17, at 13:43, Yaron Keren <yaron.keren at gmail.com> wrote:
> 
> I'm trying another approach. The non-null validation goes through a macro defined to a function which possibly may be predefined to nothing. This will disable all null checking on iterators in debug mode which is relevant to additional functions beyond std::equal. In practice it should not be a problem since if a null iterator is actually dereferenced (not only compared) then the debugger stops with invalid access anyhow. 

Well, this would be ideal :).