Merge pull request #721 from MikeMcQuaid/no_weak_imports

Set -no_weak_imports linker flag for Xcode 8

Library/Homebrew/extend/ENV/shared.rb

@@ -329,3 +329,5 @@ module SharedEnvExtension
     version && Version.create(version) >= Version.create("4.8")
   end
 end
+
+require "extend/os/extend/ENV/shared"

Library/Homebrew/extend/os/extend/ENV/shared.rb

@@ -0,0 +1,5 @@
+require "extend/ENV/shared"
+
+if OS.mac?
+  require "extend/os/mac/extend/ENV/shared"
+end

Library/Homebrew/extend/os/mac/extend/ENV/shared.rb

@@ -0,0 +1,6 @@
+module SharedEnvExtension
+  def no_weak_imports?
+    return false unless compiler == :clang
+    MacOS::Xcode.version >= "8.0" || MacOS::CLT.version >= "8.0"
+  end
+end

Library/Homebrew/extend/os/mac/extend/ENV/std.rb

@@ -28,6 +28,11 @@ module Stdenv
       # depend on it already being installed to build itself.
       ld64 if Formula["ld64"].installed?
     end
+
+    # Xcode 8 should be told to fail to link against weak links
+    # Issue from Apple engineer:
+    # https://github.com/Homebrew/homebrew-core/issues/3727
+    append "LDFLAGS", "-Wl,-no_weak_imports" if no_weak_imports?
   end
 
   def homebrew_extra_pkg_config_paths

Library/Homebrew/extend/os/mac/extend/ENV/super.rb

@@ -81,6 +81,10 @@ module Superenv
     s << "s" if MacOS.version >= :mountain_lion
     # Fix issue with >= 10.8 apr-1-config having broken paths
     s << "a" if MacOS.version >= :mountain_lion
+    # Xcode 8 should be told to fail to link against weak links
+    # Issue from Apple engineer:
+    # https://github.com/Homebrew/homebrew-core/issues/3727
+    s << "w" if no_weak_imports?
     s
   end
 

Library/Homebrew/shims/super/cc

@@ -258,8 +258,10 @@ class Cmd
     case mode
     when :ld
       args << "-headerpad_max_install_names"
+      args << "-no_weak_imports" if no_weak_imports?
     when :ccld, :cxxld
       args << "-Wl,-headerpad_max_install_names"
+      args << "-Wl,-no_weak_imports" if no_weak_imports?
     end
     args
   end
@@ -305,6 +307,10 @@ class Cmd
     config.include?("K")
   end
 
+  def no_weak_imports?
+    config.include?("w")
+  end
+
   def canonical_path(path)
     path = Pathname.new(path)
     path = path.realpath if path.exist?