brew doctor: add check for outdated compilers

A common source of build problems on Xcode 4.3+ is outdated compilers,
usually when a user has installed over top of an old version and hasn't
installed the CLT. Since the compilers from the previous Xcode are still
around, brew doctor wouldn't complain.

This adds a hash containing a list of the canonical compiler versions
for supported versions of Xcode, and adds a check against that to determine
whether a given installation has any compilers which are out of date.

Closes Homebrew#11518.

Signed-off-by: Misty De Meo <mistydemeo@gmail.com>

Library/Homebrew/cmd/doctor.rb

@@ -232,6 +232,17 @@ def check_cc
   end
 end
 
+def check_standard_compilers
+  return if check_for_latest_xcode # only check if Xcode is up to date
+  if !MacOS.compilers_standard? then <<-EOS.undent
+    Your compilers are different from the standard versions for your Xcode.
+    If you have Xcode 4.3 or newer, you should install the Command Line Tools for
+    Xcode from within Xcode's Download preferences.
+    Otherwise, you should reinstall Xcode.
+    EOS
+  end
+end
+
 def __check_subdir_access base
   target = HOMEBREW_PREFIX+base
   return unless target.exist?

Library/Homebrew/utils.rb

@@ -521,6 +521,25 @@ def mountain_lion?
   def prefer_64_bit?
     Hardware.is_64_bit? and not leopard?
   end
+
+  StandardCompilers = {
+    "3.1.4" => {:gcc_40_build_version=>5493, :gcc_42_build_version=>5577, :llvm_build_version=>2064},
+    "3.2.6" => {:gcc_40_build_version=>5494, :gcc_42_build_version=>5666, :llvm_build_version=>2335, :clang_version=>"1.7", :clang_build_version=>77},
+    "4.0.0" => {:gcc_40_build_version=>5494, :gcc_42_build_version=>5666, :llvm_build_version=>2335, :clang_version=>"2.0", :clang_build_version=>137},
+    "4.0.1" => {:gcc_40_build_version=>5494, :gcc_42_build_version=>5666, :llvm_build_version=>2335, :clang_version=>"2.0", :clang_build_version=>137},
+    "4.0.2" => {:gcc_40_build_version=>5494, :gcc_42_build_version=>5666, :llvm_build_version=>2335, :clang_version=>"2.0", :clang_build_version=>137},
+    "4.2.0" => {:llvm_build_version=>2336, :clang_version=>"3.0", :clang_build_version=>211},
+    "4.3.0" => {:llvm_build_version=>2336, :clang_version=>"3.1", :clang_build_version=>318},
+    "4.3.1" => {:llvm_build_version=>2336, :clang_version=>"3.1", :clang_build_version=>318},
+    "4.3.2" => {:llvm_build_version=>2336, :clang_version=>"3.1", :clang_build_version=>318}
+  }
+
+  def compilers_standard?
+    xcode = MacOS.xcode_version
+    return unless StandardCompilers.keys.include? xcode
+
+    StandardCompilers[xcode].all? {|k,v| MacOS.send(k) == v}
+  end
 end
 
 module GitHub extend self