macOS: -std=c++17 requires -mmacosx-version-min=10.14

[jbarlow83]

On macOS, it is not possible to compile with -std=c++17 unless -mmacosx-version-min=10.14. macOS 10.14 is Mojave, the latest version.

It would be best to select -std=c++14 on macOS since it is far more compatible with older versions. Alternately, perhaps something can be fixed in pybind11.h to improve compatibility.

If macOS version is -mmacosx-version-min=10.7, error messages like:

pybind11/pybind11.h:1011:9: error: call to unavailable function 'operator delete': introduced in macOS 10.12
        ::operator delete(p, s);
        ^~~~~~~~~~~~~~~~~

If macOS 10.12 (or 10.13) is selected, as suggested, errors (perhaps unintended) still appear:

pybind11/pybind11.h:1009:9: error: no matching function for call to 'operator delete'
        ::operator delete(p, s, std::align_val_t(a));
        ^~~~~~~~~~~~~~~~~

[NathanBWaters]

If you have this problem, simply change line 59 in setup.py from:
flags = ['-std=c++17', '-std=c++14', '-std=c++11']
to
flags = ['-std=c++14', '-std=c++11']

Thanks @jbarlow83!

[jagerman]

Leaving a note here for posterity:

Having dealt with this recently on another project, there is a fair amount of C++17 that you can get away with under -mmacosx-version-min=10.12; all the core language features are fine, but the things that you can't use (at least that I ran into) are all related to stl exceptions:

• std::optional or std::variant calls that can throw an exception. (So for instance opt.value() is not allowed, but *opt, opt.has_value(), and opt.value_or(x) are all okay).
• std::variant - similar to optional: std::holds_alternative<T>(var) is fine, var.get_if<T>(&var) is fine, but var.get<T>() is not allowed.
• std::filesystem - just don't go near it, I think even with 10.14. (https://github.com/gulrak/filesystem is a great drop-in alternative).
• std::any - not useful at all when targeting anything older than 10.14.