install glibc/gcc automatically if too old.

Right now this is done through the gcc@5 formula.
See 9692318ca6/Formula/gcc%405.rb (L33)

This is fragile because when we will migrate to gcc@11
we have to think about migrating the installation from one gcc formula to another..
Also, not having the right glibc version results in a non-functional brew
installation on an older Linux: the glibc installation needs
to be done by brew, and not by a workaround in a specific formula

Co-Authored-By: Mike McQuaid <mike@mikemcquaid.com>
Co-Authored-By: Bo Anderson <mail@boanderson.me>
Co-Authored-By: Shaun Jackman <sjackman@gmail.com>

Library/Homebrew/dependency_collector.rb

@@ -28,6 +28,8 @@ class DependencyCollector
   def initialize
     @deps = Dependencies.new
     @requirements = Requirements.new
+
+    init_global_dep_tree_if_needed!
   end
 
   def initialize_copy(other)
@@ -68,6 +70,12 @@ class DependencyCollector
     parse_spec(spec, Array(tags))
   end
 
+  sig { params(related_formula_names: T::Array[String]).returns(T.nilable(Dependency)) }
+  def gcc_dep_if_needed(related_formula_names); end
+
+  sig { params(related_formula_names: T::Array[String]).returns(T.nilable(Dependency)) }
+  def glibc_dep_if_needed(related_formula_names); end
+
   def git_dep_if_needed(tags)
     return if Utils::Git.available?
 
@@ -110,6 +118,9 @@ class DependencyCollector
 
   private
 
+  sig { void }
+  def init_global_dep_tree_if_needed!; end
+
   def parse_spec(spec, tags)
     case spec
     when String

Library/Homebrew/development_tools.rb

@@ -98,6 +98,16 @@ class DevelopmentTools
       @gcc_version = {}
     end
 
+    sig { returns(T::Boolean) }
+    def build_system_too_old?
+      false
+    end
+
+    sig { returns(T::Boolean) }
+    def system_gcc_too_old?
+      false
+    end
+
     sig { returns(T::Boolean) }
     def ca_file_handles_most_https_certificates?
       # The system CA file is too old for some modern HTTPS certificates on

Library/Homebrew/extend/os/dependency_collector.rb

@@ -1,4 +1,8 @@
 # typed: strict
 # frozen_string_literal: true
 
-require "extend/os/mac/dependency_collector" if OS.mac?
+if OS.mac?
+  require "extend/os/mac/dependency_collector"
+elsif OS.linux?
+  require "extend/os/linux/dependency_collector"
+end

Library/Homebrew/extend/os/linux/dependency_collector.rb

@@ -0,0 +1,76 @@
+# typed: true
+# frozen_string_literal: true
+
+require "os/linux/glibc"
+
+class DependencyCollector
+  extend T::Sig
+
+  undef gcc_dep_if_needed
+  undef glibc_dep_if_needed
+  undef init_global_dep_tree_if_needed!
+
+  sig { params(related_formula_names: T::Set[String]).returns(T.nilable(Dependency)) }
+  def gcc_dep_if_needed(related_formula_names)
+    return unless DevelopmentTools.system_gcc_too_old?
+    return if related_formula_names.include?(GCC)
+    return if global_dep_tree[GCC]&.intersect?(related_formula_names)
+    return if global_dep_tree[GLIBC]&.intersect?(related_formula_names) # gcc depends on glibc
+
+    Dependency.new(GCC)
+  end
+
+  sig { params(related_formula_names: T::Set[String]).returns(T.nilable(Dependency)) }
+  def glibc_dep_if_needed(related_formula_names)
+    return unless OS::Linux::Glibc.below_ci_version?
+    return if global_dep_tree[GLIBC]&.intersect?(related_formula_names)
+
+    Dependency.new(GLIBC)
+  end
+
+  private
+
+  GLIBC = "glibc"
+  GCC = CompilerSelector.preferred_gcc.freeze
+
+  # Use class variables to avoid this expensive logic needing to be done more
+  # than once.
+  # rubocop:disable Style/ClassVars
+  @@global_dep_tree = {}
+
+  sig { void }
+  def init_global_dep_tree_if_needed!
+    return unless DevelopmentTools.build_system_too_old?
+    return if @@global_dep_tree.present?
+
+    # Defined in precedence order (gcc depends on glibc).
+    global_deps = [GLIBC, GCC].freeze
+
+    @@global_dep_tree = global_deps.to_h { |name| [name, Set.new([name])] }
+
+    global_deps.each do |global_dep_name|
+      # This is an arbitrary number picked based on testing the current tree
+      # depth and just to ensure that this doesn't loop indefinitely if we
+      # introduce a circular dependency by mistake.
+      maximum_tree_depth = 10
+      current_tree_depth = 0
+
+      deps = Formula[global_dep_name].deps
+      while deps.present?
+        current_tree_depth += 1
+        if current_tree_depth > maximum_tree_depth
+          raise "maximum tree depth (#{maximum_tree_depth}) exceeded calculating #{global_dep_name} dependency tree!"
+        end
+
+        @@global_dep_tree[global_dep_name].merge(deps.map(&:name))
+        deps = deps.flat_map { |dep| dep.to_formula.deps }
+      end
+    end
+  end
+
+  sig { returns(T::Hash[String, T::Set[String]]) }
+  def global_dep_tree
+    @@global_dep_tree
+  end
+  # rubocop:enable Style/ClassVars
+end

Library/Homebrew/extend/os/linux/development_tools.rb

@@ -21,6 +21,18 @@ class DevelopmentTools
       :gcc
     end
 
+    sig { returns(T::Boolean) }
+    def build_system_too_old?
+      return @build_system_too_old if defined? @build_system_too_old
+
+      @build_system_too_old = (system_gcc_too_old? || OS::Linux::Glibc.below_ci_version?)
+    end
+
+    sig { returns(T::Boolean) }
+    def system_gcc_too_old?
+      gcc_version("gcc") < OS::LINUX_GCC_CI_VERSION
+    end
+
     sig { returns(T::Hash[String, T.nilable(String)]) }
     def build_system_info
       generic_build_system_info.merge({

Library/Homebrew/extend/os/linux/formula.rb

@@ -5,6 +5,7 @@ class Formula
   undef shared_library
   undef loader_path
   undef deuniversalize_machos
+  undef add_global_deps_to_spec
 
   sig { params(name: String, version: T.nilable(T.any(String, Integer))).returns(String) }
   def shared_library(name, version = nil)
@@ -23,4 +24,20 @@ class Formula
 
   sig { params(targets: T.nilable(T.any(Pathname, String))).void }
   def deuniversalize_machos(*targets); end
+
+  sig { params(spec: SoftwareSpec).void }
+  def add_global_deps_to_spec(spec)
+    @global_deps ||= begin
+      dependency_collector = spec.dependency_collector
+      related_formula_names = Set.new([
+        name,
+        *versioned_formulae_names,
+      ])
+      [
+        dependency_collector.gcc_dep_if_needed(related_formula_names),
+        dependency_collector.glibc_dep_if_needed(related_formula_names),
+      ].compact.freeze
+    end
+    @global_deps.each { |dep| spec.dependency_collector.add(dep) }
+  end
 end

Library/Homebrew/extend/os/linux/linkage_checker.rb

@@ -80,9 +80,5 @@ class LinkageChecker
     @unwanted_system_dylibs = @system_dylibs.reject do |s|
       SYSTEM_LIBRARY_ALLOWLIST.include? File.basename(s)
     end
-    # FIXME: Remove this when these dependencies are injected correctly (e.g. through `DependencyCollector`)
-    # See discussion at
-    #   https://github.com/Homebrew/brew/pull/13577
-    @undeclared_deps -= [CompilerSelector.preferred_gcc, "glibc", "gcc"]
   end
 end

Library/Homebrew/formula.rb

@@ -262,9 +262,13 @@ class Formula
     return unless spec.url
 
     spec.owner = self
+    add_global_deps_to_spec(spec)
     instance_variable_set("@#{name}", spec)
   end
 
+  sig { params(spec: SoftwareSpec).void }
+  def add_global_deps_to_spec(spec); end
+
   def determine_active_spec(requested)
     spec = send(requested) || stable || head
     spec || raise(FormulaSpecificationError, "formulae require at least a URL")
@@ -443,7 +447,7 @@ class Formula
   # Returns any `@`-versioned formulae names for any formula (including versioned formulae).
   sig { returns(T::Array[String]) }
   def versioned_formulae_names
-    @versioned_formulae_names ||= Pathname.glob(path.to_s.gsub(/(@[\d.]+)?\.rb$/, "@*.rb")).map do |versioned_path|
+    Pathname.glob(path.to_s.gsub(/(@[\d.]+)?\.rb$/, "@*.rb")).map do |versioned_path|
       next if versioned_path == path
 
       versioned_path.basename(".rb").to_s
@@ -453,7 +457,7 @@ class Formula
   # Returns any `@`-versioned Formula objects for any Formula (including versioned formulae).
   sig { returns(T::Array[Formula]) }
   def versioned_formulae
-    @versioned_formulae ||= versioned_formulae_names.map do |name|
+    versioned_formulae_names.map do |name|
       Formula[name]
     rescue FormulaUnavailableError
       nil

Library/Homebrew/formula_installer.rb

@@ -581,11 +581,9 @@ class FormulaInstaller
   end
 
   def expand_dependencies_for_formula(formula, inherited_options)
-    any_bottle_used = false
-
     # Cache for this expansion only. FormulaInstaller has a lot of inputs which can alter expansion.
     cache_key = "FormulaInstaller-#{formula.full_name}-#{Time.now.to_f}"
-    expanded_deps = Dependency.expand(formula, cache_key: cache_key) do |dependent, dep|
+    Dependency.expand(formula, cache_key: cache_key) do |dependent, dep|
       inherited_options[dep.name] |= inherited_options_for(dep)
       build = effective_build_options_for(
         dependent,
@@ -601,36 +599,14 @@ class FormulaInstaller
         Dependency.prune
       elsif dep.satisfied?(inherited_options[dep.name])
         Dependency.skip
-      else
-        any_bottle_used ||= install_bottle_for?(dep.to_formula, build)
       end
     end
-
-    [expanded_deps, any_bottle_used]
   end
 
   def expand_dependencies
     inherited_options = Hash.new { |hash, key| hash[key] = Options.new }
-    any_bottle_used = pour_bottle?
 
-    expanded_deps, any_dep_bottle_used = expand_dependencies_for_formula(formula, inherited_options)
-    any_bottle_used ||= any_dep_bottle_used
-
-    # We require some dependencies (glibc, GCC 5, etc.) if binaries were built.
-    # Native binaries shouldn't exist in cross-platform `all` bottles.
-    if any_bottle_used && !formula.bottled?(:all) && !Keg.bottle_dependencies.empty?
-      all_bottle_deps = Keg.bottle_dependencies.flat_map do |bottle_dep|
-        bottle_dep.recursive_dependencies.map(&:name) + [bottle_dep.name]
-      end
-
-      if all_bottle_deps.exclude?(formula.name)
-        bottle_deps = Keg.bottle_dependencies.flat_map do |bottle_dep|
-          expanded_bottle_deps, = expand_dependencies_for_formula(bottle_dep, inherited_options)
-          expanded_bottle_deps
-        end
-        expanded_deps = Dependency.merge_repeats(bottle_deps + expanded_deps)
-      end
-    end
+    expanded_deps = expand_dependencies_for_formula(formula, inherited_options)
 
     expanded_deps.map { |dep| [dep, inherited_options[dep.name]] }
   end

Library/Homebrew/keg_relocate.rb

@@ -366,17 +366,6 @@ class Keg
   def self.file_linked_libraries(_file, _string)
     []
   end
-
-  def self.bottle_dependencies
-    return [] unless Homebrew::SimulateSystem.simulating_or_running_on_linux?
-
-    @bottle_dependencies ||= begin
-      formulae = []
-      gcc = Formulary.factory(CompilerSelector.preferred_gcc)
-      formulae << gcc if DevelopmentTools.gcc_version("gcc") < gcc.version.to_i
-      formulae
-    end
-  end
 end
 
 require "extend/os/keg_relocate"

Library/Homebrew/os/linux/glibc.rb

@@ -44,6 +44,11 @@ module OS
       def below_minimum_version?
         system_version < minimum_version
       end
+
+      sig { returns(T::Boolean) }
+      def below_ci_version?
+        system_version < LINUX_GLIBC_CI_VERSION
+      end
     end
   end
 end

Library/Homebrew/software_spec.rb

@@ -50,6 +50,11 @@ class SoftwareSpec
     @uses_from_macos_elements = []
   end
 
+  def initialize_copy(other)
+    super
+    @dependency_collector = @dependency_collector.dup
+  end
+
   def owner=(owner)
     @name = owner.name
     @full_name = owner.full_name

Library/Homebrew/test/installed_dependents_spec.rb

@@ -6,7 +6,20 @@ require "installed_dependents"
 describe InstalledDependents do
   include FileUtils
 
-  def setup_test_keg(name, version)
+  def stub_formula(name, version = "1.0", &block)
+    f = formula(name) do
+      url "#{name}-#{version}"
+
+      instance_eval(&block) if block
+    end
+    stub_formula_loader f
+    stub_formula_loader f, "homebrew/core/#{f}"
+    f
+  end
+
+  def setup_test_keg(name, version, &block)
+    stub_formula(name, version, &block)
+
     path = HOMEBREW_CELLAR/name/version
     (path/"bin").mkpath
 
@@ -18,27 +31,25 @@ describe InstalledDependents do
   end
 
   let!(:keg) { setup_test_keg("foo", "1.0") }
-
-  describe "::find_some_installed_dependents" do
-    def stub_formula_name(name)
-      f = formula(name) { url "foo-1.0" }
-      stub_formula_loader f
-      stub_formula_loader f, "homebrew/core/#{f}"
-      f
+  let!(:keg_only_keg) do
+    setup_test_keg("foo-keg-only", "1.0") do
+      keg_only "a good reason"
+    end
   end
 
-    def setup_test_keg(name, version)
-      f = stub_formula_name(name)
+  describe "::find_some_installed_dependents" do
+    def setup_test_keg(name, version, &block)
       keg = super
-      Tab.create(f, DevelopmentTools.default_compiler, :libcxx).write
+      Tab.create(keg.to_formula, DevelopmentTools.default_compiler, :libcxx).write
       keg
     end
 
     before do
       keg.link
+      keg_only_keg.optlink
     end
 
-    def alter_tab(keg = dependent)
+    def alter_tab(keg)
       tab = Tab.for_keg(keg)
       yield tab
       tab.write
@@ -46,24 +57,26 @@ describe InstalledDependents do
 
     # 1.1.6 is the earliest version of Homebrew that generates correct runtime
     # dependency lists in {Tab}s.
-    def dependencies(deps, homebrew_version: "1.1.6")
-      alter_tab do |tab|
+    def tab_dependencies(keg, deps, homebrew_version: "1.1.6")
+      alter_tab(keg) do |tab|
         tab.homebrew_version = homebrew_version
-        tab.tabfile = dependent/Tab::FILENAME
+        tab.tabfile = keg/Tab::FILENAME
         tab.runtime_dependencies = deps
       end
     end
 
-    def unreliable_dependencies(deps)
+    def unreliable_tab_dependencies(keg, deps)
       # 1.1.5 is (hopefully!) the last version of Homebrew that generates
       # incorrect runtime dependency lists in {Tab}s.
-      dependencies(deps, homebrew_version: "1.1.5")
+      tab_dependencies(keg, deps, homebrew_version: "1.1.5")
     end
 
-    let(:dependent) { setup_test_keg("bar", "1.0") }
-
     specify "a dependency with no Tap in Tab" do
       tap_dep = setup_test_keg("baz", "1.0")
+      dependent = setup_test_keg("bar", "1.0") do
+        depends_on "foo"
+        depends_on "baz"
+      end
 
       # allow tap_dep to be linked too
       FileUtils.rm_r tap_dep/"bin"
@@ -71,83 +84,93 @@ describe InstalledDependents do
 
       alter_tab(keg) { |t| t.source["tap"] = nil }
 
-      dependencies nil
-      Formula["bar"].class.depends_on "foo"
-      Formula["bar"].class.depends_on "baz"
+      tab_dependencies dependent, nil
 
       result = described_class.find_some_installed_dependents([keg, tap_dep])
       expect(result).to eq([[keg, tap_dep], ["bar"]])
     end
 
     specify "no dependencies anywhere" do
-      dependencies nil
+      dependent = setup_test_keg("bar", "1.0")
+      tab_dependencies dependent, nil
       expect(described_class.find_some_installed_dependents([keg])).to be_nil
     end
 
     specify "missing Formula dependency" do
-      dependencies nil
-      Formula["bar"].class.depends_on "foo"
+      dependent = setup_test_keg("bar", "1.0") do
+        depends_on "foo"
+      end
+      tab_dependencies dependent, nil
       expect(described_class.find_some_installed_dependents([keg])).to eq([[keg], ["bar"]])
     end
 
     specify "uninstalling dependent and dependency" do
-      dependencies nil
-      Formula["bar"].class.depends_on "foo"
+      dependent = setup_test_keg("bar", "1.0") do
+        depends_on "foo"
+      end
+      tab_dependencies dependent, nil
       expect(described_class.find_some_installed_dependents([keg, dependent])).to be_nil
     end
 
     specify "renamed dependency" do
-      dependencies nil
+      dependent = setup_test_keg("bar", "1.0") do
+        depends_on "foo"
+      end
+      tab_dependencies dependent, nil
 
       stub_formula_loader Formula["foo"], "homebrew/core/foo-old"
       renamed_path = HOMEBREW_CELLAR/"foo-old"
       (HOMEBREW_CELLAR/"foo").rename(renamed_path)
-      renamed_keg = Keg.new(renamed_path/"1.0")
-
-      Formula["bar"].class.depends_on "foo"
+      renamed_keg = Keg.new(renamed_path/keg.version.to_s)
 
       result = described_class.find_some_installed_dependents([renamed_keg])
       expect(result).to eq([[renamed_keg], ["bar"]])
     end
 
     specify "empty dependencies in Tab" do
-      dependencies []
+      dependent = setup_test_keg("bar", "1.0")
+      tab_dependencies dependent, []
       expect(described_class.find_some_installed_dependents([keg])).to be_nil
     end
 
     specify "same name but different version in Tab" do
-      dependencies [{ "full_name" => "foo", "version" => "1.1" }]
+      dependent = setup_test_keg("bar", "1.0")
+      tab_dependencies dependent, [{ "full_name" => keg.name, "version" => "1.1" }]
       expect(described_class.find_some_installed_dependents([keg])).to eq([[keg], ["bar"]])
     end
 
     specify "different name and same version in Tab" do
-      stub_formula_name("baz")
-      dependencies [{ "full_name" => "baz", "version" => keg.version.to_s }]
+      stub_formula("baz")
+      dependent = setup_test_keg("bar", "1.0")
+      tab_dependencies dependent, [{ "full_name" => "baz", "version" => keg.version.to_s }]
       expect(described_class.find_some_installed_dependents([keg])).to be_nil
     end
 
     specify "same name and version in Tab" do
-      dependencies [{ "full_name" => "foo", "version" => "1.0" }]
+      dependent = setup_test_keg("bar", "1.0")
+      tab_dependencies dependent, [{ "full_name" => keg.name, "version" => keg.version.to_s }]
       expect(described_class.find_some_installed_dependents([keg])).to eq([[keg], ["bar"]])
     end
 
     specify "fallback for old versions" do
-      unreliable_dependencies [{ "full_name" => "baz", "version" => "1.0" }]
-      Formula["bar"].class.depends_on "foo"
+      dependent = setup_test_keg("bar", "1.0") do
+        depends_on "foo"
+      end
+      unreliable_tab_dependencies dependent, [{ "full_name" => "baz", "version" => "1.0" }]
       expect(described_class.find_some_installed_dependents([keg])).to eq([[keg], ["bar"]])
     end
 
     specify "non-opt-linked" do
       keg.remove_opt_record
-      dependencies [{ "full_name" => "foo", "version" => "1.0" }]
+      dependent = setup_test_keg("bar", "1.0")
+      tab_dependencies dependent, [{ "full_name" => keg.name, "version" => keg.version.to_s }]
       expect(described_class.find_some_installed_dependents([keg])).to be_nil
     end
 
     specify "keg-only" do
-      keg.unlink
-      Formula["foo"].class.keg_only "a good reason"
-      dependencies [{ "full_name" => "foo", "version" => "1.1" }] # different version
-      expect(described_class.find_some_installed_dependents([keg])).to eq([[keg], ["bar"]])
+      dependent = setup_test_keg("bar", "1.0")
+      tab_dependencies dependent, [{ "full_name" => keg_only_keg.name, "version" => "1.1" }] # different version
+      expect(described_class.find_some_installed_dependents([keg_only_keg])).to eq([[keg_only_keg], ["bar"]])
     end
 
     def stub_cask_name(name, version, dependency)