$ cc -v
Apple LLVM version 7.3.0 (clang-703.0.31)
Target: x86_64-apple-darwin15.6.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
$ cc -dM -E - < /dev/null|egrep __VERSION
#define __VERSION__ "4.2.1 Compatible Apple LLVM 7.3.0 (clang-703.0.31)"
I don't know if it is relevant, but I had to switch the following recently to address an unrelated issue.
sudo xcode-select -s /Library/Developer/CommandLineTools
|