Experimental support for non-Apple GCCs

Library/ENV/4.3/cc

@@ -68,10 +68,8 @@ class Cmd
         'clang++'
       when /llvm-gcc/
         'llvm-g++-4.2'
-      when /gcc(-4.2)?$/
-        'g++-4.2'
-      when /gcc-4.0/
-        'g++-4.0'
+      when /gcc(-\d\.\d)?$/
+        'g++' + $1.to_s
       end
     else
       @arg0

Library/Homebrew/extend/ENV/shared.rb

@@ -2,7 +2,7 @@ module SharedEnvExtension
   CC_FLAG_VARS = %w{CFLAGS CXXFLAGS OBJCFLAGS OBJCXXFLAGS}
   FC_FLAG_VARS = %w{FCFLAGS FFLAGS}
 
-  COMPILERS = ['clang', 'gcc-4.0', 'gcc-4.2', 'llvm-gcc']
+  COMPILERS = ['clang', 'gcc-4.0', 'gcc-4.2', 'llvm-gcc', /(gcc-\d\.\d)/]
   COMPLER_ALIASES = {'gcc' => 'gcc-4.2', 'llvm' => 'llvm-gcc'}
   COMPILER_SYMBOL_MAP = { 'gcc-4.0'  => :gcc_4_0,
                           'gcc-4.2'  => :gcc,
@@ -150,4 +150,28 @@ module SharedEnvExtension
     flags.each { |key| self[key] = cflags }
     set_cpu_flags(flags)
   end
+
+  def warn_about_non_apple_gcc(gcc)
+    opoo "Experimental support for non-Apple GCC enabled. Some builds may fail!"
+
+    begin
+      gcc_name = 'gcc' + gcc.delete('.')
+      gcc = Formula.factory(gcc_name)
+      if !gcc.installed?
+        raise <<-EOS.undent
+        The requested Homebrew GCC, #{gcc_name}, was not installed.
+        You must:
+          brew tap homebrew/versions
+          brew install #{gcc_name}
+        EOS
+      end
+
+      ENV.append('PATH', gcc.opt_prefix/'bin', ':')
+    rescue FormulaUnavailableError
+      raise <<-EOS.undent
+      Homebrew GCC requested, but formula #{gcc_name} not found!
+      You may need to: brew tap homebrew/versions
+      EOS
+    end
+  end
 end

Library/Homebrew/extend/ENV/std.rb

@@ -68,6 +68,10 @@ module Stdenv
       self.cxx = MacOS.locate("c++")
     end
 
+    if self['CC'] =~ GNU_GCC_REGEXP
+      warn_about_non_apple_gcc($1)
+    end
+
     # Add lib and include etc. from the current macosxsdk to compiler flags:
     macosxsdk MacOS.version
 

Library/Homebrew/extend/ENV/super.rb

@@ -109,6 +109,10 @@ module Superenv
       end
       append_path('PATH', apple_gcc42.opt_prefix/'bin') if apple_gcc42
     end
+
+    if ENV['HOMEBREW_CC'] =~ /gcc-(\d\.\d)/ && $1 != '4.2'
+      warn_about_non_apple_gcc($1)
+    end
   end
 
   def universal_binary