Unify compiler selection logic

This unifies the logic for selecting a compiler between superenv and
stdenv. A variation of superenv's `determine_cc`, which now returns a
symbol, has been moved into the shared ENV extension. Stdenv uses the
result of this directly (as it's always used symbols), while superenv
translates that back into a compiler string.

This also has the effect of disabling HOMEBREW_USE_(gcc|llvm|clang) in
stdenv, which have already been marked as deprecated for some time, and
enables the HOMEBREW_CC= environment variable syntax from superenv in
stdenv.

Library/Homebrew/extend/ENV/shared.rb

@@ -3,6 +3,11 @@ module SharedEnvExtension
   FC_FLAG_VARS = %w{FCFLAGS FFLAGS}
 
   COMPILERS = ['clang', 'gcc-4.0', 'gcc-4.2', 'llvm-gcc']
+  COMPLER_ALIASES = {'gcc' => 'gcc-4.2', 'llvm' => 'llvm-gcc'}
+  COMPILER_SYMBOL_MAP = { 'gcc-4.0'  => :gcc_4_0,
+                          'gcc-4.2'  => :gcc,
+                          'llvm-gcc' => :llvm,
+                          'clang'    => :clang }
 
   def remove_cc_etc
     keys = %w{CC CXX OBJC OBJCXX LD CPP CFLAGS CXXFLAGS OBJCFLAGS OBJCXXFLAGS LDFLAGS CPPFLAGS}
@@ -65,6 +70,33 @@ module SharedEnvExtension
   def fflags;   self['FFLAGS'];       end
   def fcflags;  self['FCFLAGS'];      end
 
+  def compiler
+    if (cc = ARGV.cc)
+      raise("Invalid value for --cc: #{cc}") if COMPILERS.grep(cc).empty?
+      COMPILER_SYMBOL_MAP.fetch(cc, cc)
+    elsif ARGV.include? '--use-gcc'
+      gcc_installed = Formula.factory('apple-gcc42').installed? rescue false
+      # fall back to something else on systems without Apple gcc
+      if MacOS.locate('gcc-4.2') || gcc_installed
+        :gcc
+      else
+        raise "gcc-4.2 not found!"
+      end
+    elsif ARGV.include? '--use-llvm'
+      :llvm
+    elsif ARGV.include? '--use-clang'
+      :clang
+    elsif self['HOMEBREW_CC']
+      cc = COMPLER_ALIASES.fetch(self['HOMEBREW_CC'], self['HOMEBREW_CC'])
+      COMPILER_SYMBOL_MAP.fetch(cc) do |invalid|
+        opoo "Invalid value for HOMEBREW_CC: #{invalid}"
+        MacOS.default_compiler
+      end
+    else
+      MacOS.default_compiler
+    end
+  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

Library/Homebrew/extend/ENV/std.rb

@@ -339,30 +339,6 @@ module Stdenv
     set_cpu_flags CC_FLAG_VARS, default, map
   end
 
-  # actually c-compiler, so cc would be a better name
-  def compiler
-    # test for --flags first so that installs can be overridden on a per
-    # install basis. Then test for ENVs in inverse order to flags, this is
-    # sensible, trust me
-    @compiler ||= if (cc = ARGV.cc)
-      COMPILERS.grep(cc).pop ? cc : raise("Invalid value for --cc: #{cc}")
-    elsif ARGV.include? '--use-gcc'
-      :gcc
-    elsif ARGV.include? '--use-llvm'
-      :llvm
-    elsif ARGV.include? '--use-clang'
-      :clang
-    elsif self['HOMEBREW_USE_CLANG']
-      :clang
-    elsif self['HOMEBREW_USE_LLVM']
-      :llvm
-    elsif self['HOMEBREW_USE_GCC']
-      :gcc
-    else
-      MacOS.default_compiler
-    end
-  end
-
   def make_jobs
     # '-j' requires a positive integral argument
     if self['HOMEBREW_MAKE_JOBS'].to_i > 0

Library/Homebrew/extend/ENV/super.rb

@@ -122,52 +122,8 @@ module Superenv
   private
 
   def determine_cc
-    if (cc = ARGV.cc)
+    cc = compiler
-      COMPILERS.grep(cc).pop ? cc : raise("Invalid value for --cc: #{cc}")
+    COMPILER_SYMBOL_MAP.invert.fetch(cc, cc)
-    elsif ARGV.include? '--use-gcc'
-      gcc_installed = Formula.factory('apple-gcc42').installed? rescue false
-      # fall back to something else on systems without Apple gcc
-      if MacOS.locate('gcc-4.2') || gcc_installed
-        "gcc-4.2"
-      else
-        raise "gcc-4.2 not found!"
-      end
-    elsif ARGV.include? '--use-llvm'
-      "llvm-gcc"
-    elsif ARGV.include? '--use-clang'
-      "clang"
-    elsif self['HOMEBREW_USE_CLANG']
-      opoo %{HOMEBREW_USE_CLANG is deprecated, use HOMEBREW_CC="clang" instead}
-      "clang"
-    elsif self['HOMEBREW_USE_LLVM']
-      opoo %{HOMEBREW_USE_LLVM is deprecated, use HOMEBREW_CC="llvm" instead}
-      "llvm-gcc"
-    elsif self['HOMEBREW_USE_GCC']
-      opoo %{HOMEBREW_USE_GCC is deprecated, use HOMEBREW_CC="gcc" instead}
-      "gcc"
-    elsif self['HOMEBREW_CC']
-      case self['HOMEBREW_CC']
-        when 'clang', 'gcc-4.0' then self['HOMEBREW_CC']
-        # depending on Xcode version plain 'gcc' could actually be
-        # gcc-4.0 or llvm-gcc
-        when 'gcc', 'gcc-4.2' then 'gcc-4.2'
-        when 'llvm', 'llvm-gcc' then 'llvm-gcc'
-      else
-        opoo "Invalid value for HOMEBREW_CC: #{self['HOMEBREW_CC'].inspect}"
-        default_cc
-      end
-    else
-      default_cc
-    end
-  end
-
-  def default_cc
-    case MacOS.default_compiler
-    when :clang   then 'clang'
-    when :llvm    then 'llvm-gcc'
-    when :gcc     then 'gcc-4.2'
-    when :gcc_4_0 then 'gcc-4.0'
-    end
   end
 
   def determine_path
@@ -288,15 +244,6 @@ module Superenv
     macosxsdk remove_macosxsdk].each{|s| alias_method s, :noop }
 
 ### DEPRECATE THESE
-  def compiler
-    case self['HOMEBREW_CC']
-      when "llvm-gcc" then :llvm
-      when "gcc-4.2" then :gcc
-      when "gcc", "clang" then self['HOMEBREW_CC'].to_sym
-    else
-      raise "Invalid value for HOMEBREW_CC: #{self['HOMEBREW_CC'].inspect}"
-    end
-  end
   def deparallelize
     delete('MAKEFLAGS')
   end