Some specific pieces of C++ support that Clang is missing:

Edit: newer link: https://clang.llvm.org/cxx_status.html

(older link, not applicable, was here)

Cross compiling for some embedded architectures.

Things like FORTRAN or Ada, calling routines built there from C (or vice versa), etc.

I don't know where you dug that up. That doc must be at least 10 years old. The clang that you get on an actual mac these days fully supports everything through C++17.

Thanks. Updated with a current link.

I've found that in certain circumstances gcc makes faster binaries

gcc usually produces slightly faster O3 binaries

macOS does not come with llvm/clang, you have to download Xcode, which you can't do anonymously, you need to create an account with Apple. Ages ago, macOS did actually come with gcc.

You can install the toolchain with `xcode-select` which does not require an Apple ID.

And if I'm not mistaken, until clang is installed commands like "clang" and "gcc" redirect to xcode-select, so if the user tries to compile something the system will offer to install the toolchain for you.

Yep. That's how I setup a new Mac. I open a terminal and type `make` and it installs the world.