os/linux/elf: avoid using ldd for listing dynamic dependencies

Library/Homebrew/os/linux/elf.rb

@@ -1,6 +1,8 @@
 # typed: true
 # frozen_string_literal: true
 
+require "os/linux/ld"
+
 # {Pathname} extension for dealing with ELF files.
 # @see https://en.wikipedia.org/wiki/Executable_and_Linkable_Format#File_header
 #
@@ -130,19 +132,7 @@ def initialize(path)
  @dylib_id, needed = needed_libraries path
  return if needed.empty?
 
- ldd = DevelopmentTools.locate "ldd"
- ldd_output = Utils.popen_read(ldd, path.expand_path.to_s).split("\n")
- return unless $CHILD_STATUS.success?
-
- ldd_paths = ldd_output.filter_map do |line|
- match = line.match(/\t.+ => (.+) \(.+\)|\t(.+) => not found/)
- next unless match
-
- match.captures.compact.first
- end
- @dylibs = ldd_paths.select do |ldd_path|
- needed.include? File.basename(ldd_path)
- end
+ @dylibs = needed.map { |lib| find_full_lib_path(lib).to_s }
  end
 
  private
@@ -157,6 +147,57 @@ def needed_libraries_using_patchelf_rb(path)
  patcher = path.patchelf_patcher
  [patcher.soname, patcher.needed]
  end
+
+ def find_full_lib_path(basename)
+ local_paths = (path.patchelf_patcher.runpath || path.patchelf_patcher.rpath)&.split(":")
+
+ # Search for dependencies in the runpath/rpath first
+ local_paths&.each do |local_path|
+ candidate = Pathname(local_path)/basename
+ return candidate if candidate.exist? && candidate.elf?
+ end
+
+ # Check if DF_1_NODEFLIB is set
+ dt_flags_1 = path.patchelf_patcher.elf.segment_by_type(:dynamic)&.tag_by_type(:flags_1)
+ nodeflib_flag = if dt_flags_1.nil?
+ false
+ else
+ dt_flags_1.value & ELFTools::Constants::DF::DF_1_NODEFLIB != 0
+ end
+
+ linker_library_paths = OS::Linux::Ld.library_paths
+ linker_system_dirs = OS::Linux::Ld.system_dirs
+
+ # If DF_1_NODEFLIB is set, exclude any library paths that are subdirectories
+ # of the system dirs
+ if nodeflib_flag
+ linker_library_paths = linker_library_paths.reject do |linker_library_path|
+ child = Pathname(linker_library_path).realdirpath
+
+ linker_system_dirs.any? do |linker_system_dir|
+ parent = Pathname(linker_system_dir).realdirpath
+ child.child_of? parent
+ end
+ end
+ end
+
+ # If not found, search recursively in the paths listed in ld.so.conf (skipping
+ # paths that are subdirectories of the system dirs if DF_1_NODEFLIB is set)
+ linker_library_paths.each do |linker_library_path|
+ candidate = Pathname(linker_library_path)/basename
+ return candidate if candidate.exist? && candidate.elf?
+ end
+
+ # If not found, search in the system dirs, unless DF_1_NODEFLIB is set
+ unless nodeflib_flag
+ linker_system_dirs.each do |linker_system_dir|
+ candidate = Pathname(linker_system_dir)/basename
+ return candidate if candidate.exist? && candidate.elf?
+ end
+ end
+
+ basename
+ end
  end
  private_constant :Metadata