Re: Using C++11

[Chris Vine <chris cvine freeserve co uk>]

On Mon, 29 Jun 2015 17:00:44 +0200
Murray Cumming <murrayc murrayc com> wrote:
[snip]
> Personally, it feels unwise for Fedora to build everything with
> --std=c ++11 if their compiler isn't going to use that by default.
> That's going to confuse developers who get weird errors when they
> don't specify --std=c++11. It's a bit like how Red Hat used to ship
> weirdly patched unstable compiler versions back in the gcc 2.* days.
> But anyway, it looks like it's happening. 

I don't disagree with the rest of your post, but this is wrong.  Using
the gcc-5.1 ABI does not require you to compile C++ code with the
-std=c++11 flag, and there is no proposal that fedora should do so.
From that point of view the _GLIBCXX_USE_CXX11_ABI define is a slight
misnomer - the point is that the ABI is compliant with C++11, not that
it is only for C++11.

The new ABI applies to all flavours of C++ compiled with the default
settings for gcc-5.1, including C++98/03 code - there is nothing in
C++98 that requires copy on write strings, nor O(N) complexity for
std::list::size() - the thing is that C++98 does not prohibit these,
whereas C++11 does.

I know my earlier posts were somewhat long, but it might be worth
reading them, as I explained all this.  I also provided some links
(which I see also Kalev reproduced for you).

Chris