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++ Compiler™ 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.)