Question: Trying to diagnose a work development laptop... What version of Clang and GCC come standard with OSX 10.10 Yosemite?

This is what I have on my Mavericks... machine, will respond with my home iMac when it boots.

```
which clang
/usr/bin/clang

which gcc
/usr/bin/gcc

clang --version
Apple LLVM version 4.2 (clang-425.0.27) (based on LLVM 3.2svn)
Target: x86_64-apple-darwin13.4.0
Thread model: posix

gcc --version
i686-apple-darwin11-llvm-gcc-4.2 (GCC) 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

```

Answer: 
On my Mac OS X 10.10.1 with the current XCode (6.1.1 (6A2008a)), I get:

```
$ /usr/bin/clang --version
Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5svn)
Target: x86_64-apple-darwin14.0.0
Thread model: posix
$ /usr/bin/gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5svn)
Target: x86_64-apple-darwin14.0.0
Thread model: posix
$

```

In other words, 'GCC' is no longer the real GNU `gcc` but is `clang`.
After many failed attempts at updating the C Compilers, we did a fresh install of Yosemite and it was fixed.

Not a great solution, but without trying to hand build Clang the sane as Mac native it was the only solution.