fix: resolve IO crashes when the parent process traps signals

CHANGELOG

@@ -1,3 +1,9 @@
+== 7.0.0-beta.13 2025-04-23
+
+Fixes:
+* Fixed a bug that caused the `FFMPEG::IO#each` method to crash when the parent process
+  was receiving and trapping exit signals.
+
 == 7.0.0-beta.12 2025-04-15
 
 Breaking Changes:

lib/ffmpeg.rb

@@ -32,15 +32,6 @@
 require_relative 'ffmpeg/transcoder'
 require_relative 'ffmpeg/version'
 
-if RUBY_PLATFORM =~ /(win|w)(32|64)$/
-  begin
-    require 'win32/process'
-  rescue LoadError
-    'Warning: ffmpeg is missing the win32-process gem to properly handle hanging transcodings. ' \
-    'Install the gem (in Gemfile if using bundler) to avoid errors.'
-  end
-end
-
 # The FFMPEG module allows you to customise the behaviour of the FFMPEG library,
 # and provides a set of methods to directly interact with the ffmpeg and ffprobe binaries.
 #
@@ -51,8 +42,6 @@
 #   FFMPEG.ffmpeg_binary = '/usr/local/bin/ffmpeg'
 #   FFMPEG.ffprobe_binary = '/usr/local/bin/ffprobe'
 module FFMPEG
-  SIGKILL = RUBY_PLATFORM =~ /(win|w)(32|64)$/ ? 1 : 'SIGKILL'
-
   class << self
     attr_writer :logger, :reporters
     attr_accessor :threads, :timeout
@@ -145,7 +134,7 @@ def ffmpeg_popen3(*args, &)
     # Execute a ffmpeg command.
     #
     # @param args [Array<String>] The arguments to pass to ffmpeg.
-    # @param reporters [Array<FFMPEG::Reporters::Output>] The reporters to use to parse the output.
+    # @param reporters [Array<Class<FFMPEG::Reporters::Output>>] The reporters to use to parse the output.
     # @yield [report] Reports from the ffmpeg command (see FFMPEG::Reporters).
     # @return [FFMPEG::Status]
     def ffmpeg_execute(*args, status: nil, reporters: nil, timeout: nil)

lib/ffmpeg/io.rb

@@ -55,21 +55,27 @@ def popen3(*cmd, &block)
     end
 
     def each(chomp: false, &block)
-      buffer = String.new
+      # We need to run this loop in a separate thread to avoid
+      # errors with exit signals being sent to the main thread.
+      Thread.new do
+        Thread.current.report_on_exception = false
 
-      until eof?
-        char = getc
-        case char
-        when "\r", "\n"
-          buffer << ($ORS || "\n") unless chomp
-          block.call(buffer) unless buffer.empty?
-          buffer = String.new
-        else
-          buffer << FFMPEG::IO.encode!(char)
+        buffer = String.new
+
+        until eof?
+          char = getc
+          case char
+          when "\r", "\n"
+            buffer << ($ORS || "\n") unless chomp
+            block.call(buffer) unless buffer.empty?
+            buffer.clear
+          else
+            buffer << FFMPEG::IO.encode!(char)
+          end
         end
-      end
 
-      block.call(buffer) unless buffer.empty?
+        block.call(buffer) unless buffer.empty?
+      end.value
     end
   end
 end

lib/ffmpeg/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module FFMPEG
-  VERSION = '7.0.0-beta.12'
+  VERSION = '7.0.0-beta.13'
 end

spec/ffmpeg_spec.rb

@@ -53,30 +53,17 @@
   end
 
   describe '.ffmpeg_execute' do
-    let(:args) { ['-i', fixture_media_file('hello.wav'), '-f', 'null', '/dev/null'] }
-
-    it 'returns the process status and yields reports' do
-      reports = []
-
-      status = described_class.ffmpeg_execute(
-        *args,
-        reporters: [FFMPEG::Reporters::Output]
-      ) do |report|
-        reports << report
-      end
+    it 'returns the process status' do
+      args = ['-i', fixture_media_file('hello.wav'), '-f', 'null', '-']
+      status = described_class.ffmpeg_execute(*args)
 
       expect(status).to be_a(FFMPEG::Status)
       expect(status.exitstatus).to eq(0)
-      expect(reports.length).to be >= 1
     end
 
     context 'when ffmpeg hangs' do
       before do
-        FFMPEG.ffmpeg_binary = fixture_file('bin/ffmpeg-hanging')
-      end
-
-      after do
-        FFMPEG.ffmpeg_binary = nil
+        described_class.ffmpeg_binary = fixture_file('bin/mock-ffmpeg')
       end
 
       context 'with IO timeout set' do
@@ -89,21 +76,57 @@
         end
 
         it 'raises IO::TimeoutError' do
-          expect { described_class.ffmpeg_execute(*args) }.to raise_error(IO::TimeoutError)
+          expect { described_class.ffmpeg_execute!('hello', 'world') }.to raise_error(IO::TimeoutError)
         end
       end
 
       context 'with operation timeout set' do
         it 'raises Timeout::Error' do
-          expect { described_class.ffmpeg_execute(*args, timeout: 0.5) }.to raise_error(Timeout::Error)
+          expect { described_class.ffmpeg_execute!('hello', 'world', timeout: 0.5) }.to raise_error(Timeout::Error)
         end
       end
     end
   end
 
   describe '.ffmpeg_execute!' do
     it 'raises an error when the process is unsuccessful' do
-      expect { FFMPEG.ffmpeg_execute!('-v') }.to raise_error(FFMPEG::Error)
+      expect { described_class.ffmpeg_execute!('-v') }.to raise_error(FFMPEG::Error)
+    end
+
+    context 'when called in a subprocess' do
+      before do
+        described_class.ffmpeg_binary = fixture_file('bin/mock-ffmpeg')
+      end
+
+      context 'with exit signal traps' do
+        it 'does not raise an error' do
+          pid = fork do
+            Signal.trap('QUIT') {} # rubocop:disable Lint/EmptyBlock
+
+            described_class.ffmpeg_execute!('-n=3', '-progress', 'hello', 'world')
+          end
+
+          sleep 1
+          Process.kill('QUIT', pid)
+          Process.wait(pid)
+
+          expect($CHILD_STATUS&.exitstatus).to eq(0)
+        end
+      end
+
+      context 'without exit signal traps' do
+        it 'does not raise an error' do
+          pid = fork do
+            described_class.ffmpeg_execute!('-n=10', '-progress', 'hello', 'world')
+          end
+
+          sleep 1
+          Process.kill('QUIT', pid)
+          _, status = Process.wait2(pid)
+
+          expect(status.exitstatus).not_to eq(0)
+        end
+      end
     end
   end
 

spec/fixtures/bin/ffmpeg-hanging → spec/fixtures/bin/mock-ffmpeg

@@ -1,6 +1,18 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
+def iterations
+  return @iterations if defined?(@iterations)
+
+  @iterations ||= ARGV.find { |arg| arg =~ /-n/ }&.split('=')&.last&.to_i
+end
+
+def progress?
+  return @progress if defined?(@progress)
+
+  @progress ||= ARGV.include?('-progress')
+end
+
 warn <<~OUTPUT
   ffmpeg version 0.11.1 Copyright (c) 2000-2012 the FFmpeg developers
     built on Jun 27 2012 11:39:49 with llvm_gcc 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2335.15.00)
@@ -29,17 +41,17 @@ warn <<~OUTPUT
       Metadata:
         creation_time   : 1970-01-01 00:00:00
         handler_name    : SoundHandler
-OUTPUT
-
-if ARGV.length > 2 # looks like we're trying to transcode
-  warn <<-OUTPUT
   Stream mapping:
     Stream #0:0 -> #0:0 (h264 -> libx264)
     Stream #0:1 -> #0:1 (aac -> libfaac)
   Press [q] to stop, [?] for help
-  OUTPUT
-  $stderr.write 'frame=   72 fps=0.0 q=32766.0 Lsize=     115kB time=00:00:07.00 bitrate= 134.6kbits/s'
-  loop { sleep 1 }
-else
-  warn 'At least one output file must be specified'
+OUTPUT
+
+n = 0
+loop do
+  $stderr.write 'frame=0 fps=0.0 q=0.0 Lsize=0kB time=00:00:00.00 bitrate=0.0kbits/s' if progress?
+
+  break if iterations && (n += 1) > iterations
+
+  sleep 1
 end

spec/spec_helper.rb

@@ -6,7 +6,6 @@
 require 'bundler'
 Bundler.require
 
-require 'debug'
 require 'fileutils'
 require 'uri'
 require 'webmock/rspec'