[PATCH] Add observers to Input Graph

[Michael Spencer]

On Tue, May 13, 2014 at 1:57 AM, Michael Spencer <bigcheesegs at gmail.com> wrote:
> ================
> Comment at: include/lld/Core/InputGraph.h:74
> @@ +73,3 @@
> +  /// being returned.
> +  void registerObserver(std::function<void(File *)> &fn);
> +
> ----------------
> 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.
>
> http://reviews.llvm.org/D3735
>
>

Clang on Windows doesn't support RTTI, and std::function requires RTTI
in VC. As this is a supported compiler, we can't use std::function
until clang on Windows supports it.

- Michael Spencer