3 files changed, 68 insertions, 19 deletions

diff --git a/Library/Homebrew/compilers.rb b/Library/Homebrew/compilers.rb
index 9561fc0fb..cb7d74334 100644
--- a/Library/Homebrew/compilers.rb
+++ b/Library/Homebrew/compilers.rb
@@ -1,30 +1,55 @@
 class Compiler < Struct.new(:name, :priority)
-  def build
-    MacOS.send("#{name}_build_version")
+  # The full version of the compiler for comparison purposes.
+  def version
+    if name.is_a? String
+      MacOS.non_apple_gcc_version(name)
+    else
+      MacOS.send("#{name}_build_version")
+    end
   end
 
-  def version
-    MacOS.non_apple_gcc_version(name) if name.is_a? String
+  # This is exposed under the `build` name for compatibility, since
+  # `fails_with` continues to use `build` in the public API.
+  # `build` indicates the build number of an Apple compiler.
+  # This is preferred over version numbers since there are often
+  # significant differences within the same version,
+  # e.g. GCC 4.2 build 5553 vs 5666.
+  # Non-Apple compilers don't have build numbers.
+  alias_method :build, :version
+
+  # The major version for non-Apple compilers. Used to indicate a compiler
+  # series; for instance, if the version is 4.8.2, it would return "4.8".
+  def major_version
+    version.match(/(\d\.\d)/)[0] if name.is_a? String
   end
 end
 
 class CompilerFailure
-  attr_reader :compiler, :version
-  attr_rw :build, :cause
+  attr_reader :compiler, :major_version
+  attr_rw :cause, :version
 
   def initialize compiler, &block
     # Non-Apple compilers are in the format fails_with compiler => version
     if compiler.is_a? Hash
       # currently the only compiler for this case is GCC
-      _, @version = compiler.shift
-      @compiler = 'gcc-' + @version.match(/(\d\.\d)/)[0]
+      _, @major_version = compiler.shift
+      @compiler = 'gcc-' + @major_version
     else
       @compiler = compiler
     end
 
     instance_eval(&block) if block_given?
-    @build = (@build || 9999).to_i unless compiler.is_a? Hash
+    if !compiler.is_a? Hash
+      @version = (@version || 9999).to_i
+    else
+      # so fails_with :gcc => '4.8' simply marks all 4.8 releases incompatible
+      @version ||= @major_version + '.999' if compiler.is_a? Hash
+    end
   end
+
+  # Allows Apple compiler `fails_with` statements to keep using `build`
+  # even though `build` and `value` are the same internally
+  alias_method :build, :version
 end
 
 class CompilerQueue
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 672d21056..f9de49adb 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -241,12 +241,10 @@ class Formula
   def fails_with? cc
     cc = Compiler.new(cc) unless cc.is_a? Compiler
     (self.class.cc_failures || []).any? do |failure|
-      if cc.version
-        # non-Apple GCCs don't have builds, just version numbers
-        failure.compiler == cc.name && failure.version >= cc.version
-      else
-        failure.compiler == cc.name && failure.build >= cc.build
-      end
+      # Major version check distinguishes between, e.g.,
+      # GCC 4.7.1 and GCC 4.8.2, where a comparison is meaningless
+      failure.compiler == cc.name && failure.major_version == cc.major_version && \
+        failure.version >= cc.version
     end
   end
 
@@ -785,6 +783,33 @@ class Formula
       @keg_only_reason = KegOnlyReason.new(reason, explanation.to_s.chomp)
     end
 
+    # For Apple compilers, this should be in the format:
+    # fails_with compiler do
+    #   cause "An explanation for why the build doesn't work."
+    #   build "The Apple build number for the newest incompatible release."
+    # end
+    #
+    # The block may be omitted, and if present the build may be omitted;
+    # if so, then the compiler will be blacklisted for *all* versions.
+    #
+    # For GNU GCC compilers, this should be in the format:
+    # fails_with compiler => major_version do
+    #   cause
+    #   version "The official release number for the latest incompatible
+    #            version, for instance 4.8.1"
+    # end
+    # 
+    # `major_version` should be the major release number only, for instance
+    # '4.8' for the GCC 4.8 series (4.8.0, 4.8.1, etc.).
+    # If `version` or the block is omitted, then the compiler will be
+    # blacklisted for all compilers in that series.
+    #
+    # For example, if a bug is only triggered on GCC 4.8.1 but is not
+    # encountered on 4.8.2:
+    # 
+    # fails_with :gcc => '4.8' do
+    #   version '4.8.1'
+    # end
     def fails_with compiler, &block
       @cc_failures ||= Set.new
       @cc_failures << CompilerFailure.new(compiler, &block)
diff --git a/Library/Homebrew/test/test_fails_with.rb b/Library/Homebrew/test/test_fails_with.rb
index 31f318a4c..642d9c060 100644
--- a/Library/Homebrew/test/test_fails_with.rb
+++ b/Library/Homebrew/test/test_fails_with.rb
@@ -3,7 +3,7 @@ require 'test/testball'
 
 class FailsWithTests < Test::Unit::TestCase
   class Double < Compiler
-    attr_accessor :name, :build, :version
+    attr_accessor :name, :version
   end
 
   def assert_fails_with(cc)
@@ -21,8 +21,7 @@ class FailsWithTests < Test::Unit::TestCase
   def build_cc(sym, build, version=nil)
     cc = Double.new
     cc.name = sym
-    cc.build = build
-    cc.version = version
+    cc.version = version || build
     cc
   end
 
@@ -49,7 +48,7 @@ class FailsWithTests < Test::Unit::TestCase
   end
 
   def test_non_apple_gcc_version
-    fails_with(:gcc => '4.8.2')
+    fails_with(:gcc => '4.8')
     cc = build_cc("gcc-4.8", nil, "4.8.1")
     assert_fails_with cc
   end