Make --cc override the compiler selector

Library/Homebrew/compilers.rb

@@ -80,11 +80,14 @@ class CompilerSelector
     :gcc_4_0 => [:gcc_4_0, :gcc, :llvm, :gnu, :clang],
   }
 
-  def self.select_for(formula)
-    compilers = COMPILER_PRIORITY.fetch(MacOS.default_compiler)
+  def self.select_for(formula, compilers=self.compilers)
     new(formula, MacOS, compilers).compiler
   end
 
+  def self.compilers
+    COMPILER_PRIORITY.fetch(MacOS.default_compiler)
+  end
+
   attr_reader :formula, :failures, :versions, :compilers
 
   def initialize(formula, versions, compilers)

Library/Homebrew/extend/ENV/shared.rb

@@ -27,6 +27,10 @@ module SharedEnvExtension
     GOBIN
   ]
 
+  def setup_build_environment(formula=nil)
+    @formula = formula
+  end
+
   def reset
     SANITIZED_VARS.each { |k| delete(k) }
   end
@@ -101,15 +105,21 @@ module SharedEnvExtension
   def fcflags;  self['FCFLAGS'];      end
 
   def compiler
-    @compiler ||= if (cc = ARGV.cc || homebrew_cc)
-      COMPILER_SYMBOL_MAP.fetch(cc) do |other|
-        case other
-        when GNU_GCC_REGEXP
-          other
-        else
-          raise "Invalid value for --cc: #{other}"
-        end
+    @compiler ||= if (cc = ARGV.cc)
+      warn_about_non_apple_gcc($1) if cc =~ GNU_GCC_REGEXP
+      fetch_compiler(cc, "--cc")
+    elsif (cc = homebrew_cc)
+      warn_about_non_apple_gcc($1) if cc =~ GNU_GCC_REGEXP
+      compiler = fetch_compiler(cc, "HOMEBREW_CC")
+
+      if @formula
+        compilers = [compiler] + CompilerSelector.compilers
+        compiler = CompilerSelector.select_for(@formula, compilers)
       end
+
+      compiler
+    elsif @formula
+      CompilerSelector.select_for(@formula)
     else
       MacOS.default_compiler
     end
@@ -127,13 +137,6 @@ module SharedEnvExtension
     end
   end
 
-  # If the given compiler isn't compatible, will try to select
-  # an alternate compiler, altering the value of environment variables.
-  # If no valid compiler is found, raises an exception.
-  def validate_cc!(formula)
-    send CompilerSelector.select_for(formula)
-  end
-
   # Snow Leopard defines an NCURSES value the opposite of most distros
   # See: http://bugs.python.org/issue6848
   # Currently only used by aalib in core
@@ -260,4 +263,15 @@ module SharedEnvExtension
   def homebrew_cc
     self["HOMEBREW_CC"]
   end
+
+  def fetch_compiler(value, source)
+    COMPILER_SYMBOL_MAP.fetch(value) do |other|
+      case other
+      when GNU_GCC_REGEXP
+        other
+      else
+        raise "Invalid value for #{source}: #{other}"
+      end
+    end
+  end
 end

Library/Homebrew/extend/ENV/std.rb

@@ -16,6 +16,7 @@ module Stdenv
   end
 
   def setup_build_environment(formula=nil)
+    super
     reset
 
     if MacOS.version >= :mountain_lion
@@ -55,10 +56,8 @@ module Stdenv
     append 'LDFLAGS', '-Wl,-headerpad_max_install_names'
 
     send(compiler)
-    validate_cc!(formula) unless formula.nil?
 
     if cc =~ GNU_GCC_REGEXP
-      warn_about_non_apple_gcc($1)
       gcc_formula = gcc_version_formula($1)
       append_path "PATH", gcc_formula.opt_bin.to_s
     end

Library/Homebrew/extend/ENV/super.rb

@@ -34,11 +34,10 @@ module Superenv
   end
 
   def setup_build_environment(formula=nil)
+    super
     reset
+    send(compiler)
 
-    self.cc  = determine_cc
-    self.cxx = determine_cxx
-    validate_cc!(formula) unless formula.nil?
     self['MAKEFLAGS'] ||= "-j#{determine_make_jobs}"
     self['PATH'] = determine_path
     self['PKG_CONFIG_PATH'] = determine_pkg_config_path
@@ -85,8 +84,6 @@ module Superenv
     # On 10.8 and newer, these flags will also be present:
     # s - apply fix for sed's Unicode support
     # a - apply fix for apr-1-config path
-
-    warn_about_non_apple_gcc($1) if homebrew_cc =~ GNU_GCC_REGEXP
   end
 
   private