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clang++ -v says
Apple LLVM version 10.0.0 (clang-1000.11.45.5) Target: x86_64-apple-darwin17.7.0 Thread model: posix InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin(edited)
bash-3.2$ clang++ -v Apple clang version 12.0.0 (clang-1200.0.31.1) Target: x86_64-apple-darwin19.6.0 Thread model: posix InstalledDir: /Library/Developer/CommandLineTools/usr/bin