Only track C++ stdlibs for C++ code

After a formula is built, scan all mach-o files for dynamic links
to see if any of them point to a C++ stdlib (libc++ or libstdc++).
If one of them is linked, record that information in the formula's tab.

This replaces the old behaviour where all files were assumed to be C++
code, and stdlibs were always tracked regardless of whether they were
actually linked against.

This also modifies the way that tabs are written - now tabs are written
with the stdlib field null, and values are only written if an stdlib
is detected.

1 files changed, 15 insertions, 0 deletions

diff --git a/Library/Homebrew/keg_fix_install_names.rb b/Library/Homebrew/keg_fix_install_names.rb
index fdb348608..3b37ccf26 100644
--- a/Library/Homebrew/keg_fix_install_names.rb
+++ b/Library/Homebrew/keg_fix_install_names.rb
@@ -42,6 +42,21 @@ class Keg
     end
   end
 
+  # Detects the C++ dynamic libraries in place, scanning the dynamic links
+  # of the files within the keg.
+  # Note that this doesn't attempt to distinguish between libstdc++ versions,
+  # for instance between Apple libstdc++ and GNU libstdc++
+  def detect_cxx_stdlibs
+    results = Set.new
+    mach_o_files.each do |file|
+      dylibs = file.dynamically_linked_libraries
+      results << :libcxx unless dylibs.grep(/libc\+\+.+\.dylib/).empty?
+      results << :libstdcxx unless dylibs.grep(/libstdc\+\+.+\.dylib/).empty?
+    end
+
+    results.to_a
+  end
+
   private
 
   OTOOL_RX = /\t(.*) \(compatibility version (\d+\.)*\d+, current version (\d+\.)*\d+\)/