From 23971854b02088bace7aadeeed4cff3ed8561e17 Mon Sep 17 00:00:00 2001
From: Mike McQuaid <mike@mikemcquaid.com>
Date: Tue, 5 Aug 2025 15:19:07 +0100
Subject: [PATCH] Fix file descriptor leak in Linux LD library path parsing
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The library_paths method was using readlines which could leave file
descriptors open due to Ruby's garbage collection behavior. When
processing many packages during 'brew upgrade' or 'brew linkage',
this caused "Too many open files" errors on Linux systems.

Changes:
- Replace readlines with explicit file.open block to ensure proper closure
- Add caching to avoid repeatedly reading /etc/ld.so.conf during a session
- Cache included files as well to optimize recursive include processing

Fixes: #19866, #20302, #19177, #20223

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
---
 Library/Homebrew/os/linux/ld.rb | 36 ++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/Library/Homebrew/os/linux/ld.rb b/Library/Homebrew/os/linux/ld.rb
index b4a033b962..ce0e21fcbf 100644
--- a/Library/Homebrew/os/linux/ld.rb
+++ b/Library/Homebrew/os/linux/ld.rb
@@ -50,29 +50,37 @@ module OS
         conf_file = Pathname(conf_path)
         return [] unless conf_file.exist?
 
+        @library_paths_cache ||= T.let({}, T.nilable(T::Hash[String, T::Array[String]]))
+        cache_key = conf_file.to_s
+        if (cached_library_path_contents = @library_paths_cache[cache_key])
+          return cached_library_path_contents
+        end
+
         paths = Set.new
         directory = conf_file.realpath.dirname
 
-        conf_file.readlines.each do |line|
-          # Remove comments and leading/trailing whitespace
-          line.strip!
-          line.sub!(/\s*#.*$/, "")
+        conf_file.open("r") do |file|
+          file.each_line do |line|
+            # Remove comments and leading/trailing whitespace
+            line.strip!
+            line.sub!(/\s*#.*$/, "")
 
-          if line.start_with?(/\s*include\s+/)
-            include_path = Pathname(line.sub(/^\s*include\s+/, "")).expand_path
-            wildcard = include_path.absolute? ? include_path : directory/include_path
+            if line.start_with?(/\s*include\s+/)
+              include_path = Pathname(line.sub(/^\s*include\s+/, "")).expand_path
+              wildcard = include_path.absolute? ? include_path : directory/include_path
 
-            Dir.glob(wildcard.to_s).each do |include_file|
-              paths += library_paths(include_file)
+              Dir.glob(wildcard.to_s).each do |include_file|
+                paths += library_paths(include_file)
+              end
+            elsif line.empty?
+              next
+            else
+              paths << line
             end
-          elsif line.empty?
-            next
-          else
-            paths << line
           end
         end
 
-        paths.to_a
+        @library_paths_cache[cache_key] = paths.to_a
       end
     end
   end