Re: Opinions on introduction of string_view in Core

From: Gavin Lambert (boost_at_[hidden])
Date: 2021-10-19 23:20:52

On 20/10/2021 01:27, Peter Dimov wrote:
>> That said, compiling parts of the same program with different C++
>> standards is asking for trouble.  I would expect ODR violations from the
>> standard library in that case.
> 
> People do that every day, sometimes without even realizing it.

Any time you're using a system-provided C++ library, you're doing this. 
  And that includes system-provided Boost.

It's fairly commonplace to compile an app with a higher C++ standard 
than was used for the system libraries, because those tend to be built 
with conservative defaults.

The reverse is also possible, but less common, since if a library 
requires a higher C++ standard to build itself then this usually means 
consumers of the library need at least that or higher too.  Still, this 
is not guaranteed; a library might be using some features only in its 
source files and not its public headers.

And I've seen quite a few libraries where only a subset of source files 
are compiled with a higher standard level than the others.

(Things are a bit different here between *nix and Windows.  Most *nix 
distros designate a One True C++ Compilerâ„¢ for their current release, 
including a default C++ standard level and library, and most things are 
built to this, so it's easier to rely on prebuilt system libraries. 
Whereas on Windows there is no standard C++ compiler or library, so it's 
more commonplace to either "build the world" and distribute private 
binaries or to rely on the C or COM ABIs instead of the C++ ABI, since 
those are more stable.)