[PATCH] Add observers to Input Graph

[Duncan P. N. Exon Smith]

+richard, who added the current guidance in r208067.

On 2014-May-13, at 00:57, Michael Spencer <bigcheesegs at gmail.com> wrote:

> Simon Atanasyan wrote:
>> Maybe it is better to use the `llvm::function_ref` class to be consistent with main LLVM code.
>> 
>> http://llvm.org/docs/ProgrammersManual.html#passing-functions-and-other-callable-objects
> This is news to me. I would much prefer we use std::function.
> 
> So after doing some research, it seems that advanced uses of std::function can fail on VC11 (VS 2012). We're not doing that here, and the buildbots have the final say in what is supported.

The programmer's manual is pretty clear about disallowing std::function.
It's great if we can use it, but it might deserve a thread on llvm-dev,
and the guidance in ProgrammersManual.rst should be updated.

Unless lld follows a different policy here?

> std::function
> 
> You cannot use std::function within LLVM code, because it is not supported by all our target toolchains.