[llvm-commits] [llvm] r168211 - /llvm/trunk/include/llvm/Attributes.h

[Chris Lattner]

On Nov 25, 2012, at 10:17 AM, David Blaikie <dblaikie at gmail.com> wrote:

> On Sun, Nov 25, 2012 at 9:06 AM, Chris Lattner <clattner at apple.com> wrote:
>> 
>> On Nov 16, 2012, at 2:22 PM, Benjamin Kramer <benny.kra at googlemail.com> wrote:
>> 
>>> Author: d0k
>>> Date: Fri Nov 16 16:22:20 2012
>>> New Revision: 168211
>>> 
>>> URL: http://llvm.org/viewvc/llvm-project?rev=168211&view=rev
>>> Log:
>>> Remove default public copy ctors.
>>> 
>>> They are just useless and prevent SmallVector from picking an optimized codepath
>>> for memcpyable elements.
>> 
>> Is this something that Clang could conceivably warn about?
> 
> +1 (generalized to all special member functions that can be provided
> implicitly, possibly with a fixit/text to suggest removal and/or a
> fixit to suggest "= default" (under C++11))
> 
> It's perhaps a little on the "stylistic" end, though we could restrict
> it to cases where the explicit definition disables move operations
> only (to get the meatier/important cases). Separate version for when
> this explicit definition causes a type to become
> non-standard-layout/pod/trivial/etc or other useful traits.

I think that most useful version would be to only warn about types with copy constructors that are actually *used* in a type trait checking for triviality, to avoid massive spam in codebases where it wouldn't help anyway (e.g. building with an old libstdc++).  David, can you file a PR to track this if you think it would be useful? :)

-Chris