brew update -v

brew doctor

$ brew doctor
Error: undefined method `<' for nil:NilClass
Please report this bug: https://github.com/mxcl/homebrew/wiki/Checklist-before-filing-a-new-issue
/usr/local/Library/Homebrew/cmd/doctor.rb:197:in `check_gcc_versions'
/usr/local/Library/Homebrew/cmd/doctor.rb:735:in `doctor'
/usr/local/bin/brew:82:in `send'
/usr/local/bin/brew:82

gistfile1.txt

 brew upgrade -v
==> Downloading http://www.cmake.org/files/v2.8/cmake-2.8.5.tar.gz
File already downloaded in /Users/ptarjan/Library/Caches/Homebrew
/usr/bin/tar xf /Users/ptarjan/Library/Caches/Homebrew/cmake-2.8.5.tar.gz
==> ./bootstrap --prefix=/usr/local/Cellar/cmake/2.8.5 --system-libs --no-system-libarchive --datadir=/share/cmake --docdir=/share/doc/cmake --mandir=/share/man
./bootstrap --prefix=/usr/local/Cellar/cmake/2.8.5 --system-libs --no-system-libarchive --datadir=/share/cmake --docdir=/share/doc/cmake --mandir=/share/man
---------------------------------------------
CMake 2.8.5, Copyright 2000-2009 Kitware, Inc.
---------------------------------------------
Error when bootstrapping CMake:
Cannot find appropriate C compiler on this system.
Please specify one using environment variable CC.
See cmake_bootstrap.log for compilers attempted.

---------------------------------------------
Log of errors: /private/tmp/homebrew-cmake-2.8.5-hwgn/cmake-2.8.5/Bootstrap.cmk/cmake_bootstrap.log
---------------------------------------------
==> Exit Status: 6
http://github.com/mxcl/homebrew/blob/master/Library/Formula/cmake.rb#L27
==> Environment
HOMEBREW_VERSION: 0.8
HEAD: eb98c44a697ad13b6c994f09de06dbd52cca3aa8
HOMEBREW_PREFIX: /usr/local
HOMEBREW_CELLAR: /usr/local/Cellar
HOMEBREW_REPOSITORY: /usr/local
HOMEBREW_LIBRARY_PATH: /usr/local/Library/Homebrew
Hardware: dual-core 64-bit penryn
OS X: 10.7
Kernel Architecture: x86_64
Ruby: 1.8.7-249
/usr/bin/ruby => /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby
Xcode: 

GCC-4.0: N/A 
GCC-4.2: N/A 
LLVM: build 2335 
MacPorts or Fink? false
X11 installed? true
==> Build Flags
CC: /usr/bin/cc
CXX: /usr/bin/c++
LD: /usr/bin/cc
CFLAGS: -O3 -march=core2 -msse4.1 -w -pipe
CXXFLAGS: -O3 -march=core2 -msse4.1 -w -pipe
MAKEFLAGS: -j2

Error: Failed executing: ./bootstrap --prefix=/usr/local/Cellar/cmake/2.8.5 --system-libs --no-system-libarchive --datadir=/share/cmake --docdir=/share/doc/cmake --mandir=/share/man
Please report this bug: https://github.com/mxcl/homebrew/wiki/Checklist-before-filing-a-new-issue
These existing issues may help you:
https://github.com/mxcl/homebrew/issues/#issue/5940
https://github.com/mxcl/homebrew/issues/#issue/6352

Also try:
  `brew doctor` to check your setup for common problems.
  `brew missing` to check installed packages for missing deps.