> I know Clang struggled to ship improved sorts for their C++ implementation
Clang has no built-in sorting algorithms.
I imagine you're referring to the LLVM project's libc++?
Though all common distributions of LLVM default to GCC's libstdc++.
Fair enough, I'm not from the US. Globally they're at a roughly 10% market share and where I'm from closer to just 5%. It's a rarity to see any here and I've never gotten to try macOS outside a shop.
Clang has no built-in sorting algorithms. I imagine you're referring to the LLVM project's libc++? Though all common distributions of LLVM default to GCC's libstdc++.