Choose lldb over gdb and find proper extension of library

bin/gdb_wrapper

@@ -13,6 +13,22 @@ options = OpenStruct.new(
     'gems_to_include' => []
 )
 
+module DebugPrinter
+
+  class << self
+    attr_accessor :cli_debug
+
+    def print_debug(msg)
+      if DebugPrinter.cli_debug
+        $stderr.puts msg
+      end
+    end
+  end
+
+end
+
+DebugPrinter.cli_debug = ARGV.include? '--debug'
+
 opts = OptionParser.new do |opts|
   # TODO need some banner
   opts.banner = <<EOB
@@ -75,17 +91,31 @@ class NativeDebugger
     if debase_path.size == 0
       raise 'No debase gem found.'
     end
-    @path_to_attach = debase_path[0] + '/attach.so'
+    @path_to_attach = find_attach_lib(debase_path[0])
 
     @gems_to_include = '["' + gems_to_include * '", "' + '"]'
     @debugger_loader_path = debugger_loader_path
     @argv = argv
 
+    @eval_string = "rb_eval_string_protect(\"require '#{@debugger_loader_path}'; load_debugger(#{@gems_to_include.gsub("\"", "'")}, #{@argv.gsub("\"", "'")})\", (int *)0)"
+
     launch_string = "#{self} #{executable} #{flags}"
     @pipe = IO.popen(launch_string, 'r+')
     $stdout.puts "executed '#{launch_string}'"
   end
 
+  def find_attach_lib(debase_path)
+    attach_lib = debase_path + '/attach'
+    known_extensions = %w(.so .bundle .dll)
+    known_extensions.each do |ext|
+      if File.file?(attach_lib + ext)
+        return attach_lib + ext
+      end
+    end
+
+    raise 'Could not find attach library'
+  end
+
   def attach_to_process
     execute "attach #{@pid}"
   end
@@ -101,15 +131,17 @@ class NativeDebugger
 
   def get_response
     # we need this hack to understand that debugger gave us all output from last executed command
-    @pipe.puts "print \"#{@delimiter}\""
+    print_delimiter
 
     content = ''
     loop do
       line = @pipe.readline
+      break if check_delimiter(line)
+      DebugPrinter.print_debug('respond line: ' + line)
       next if line =~ /\(lldb\)/ # lldb repeats your input to its output
-      break if line =~ /\$\d+\s=\s"#{@delimiter}"/
       content += line
     end
+
     content
   end
 
@@ -121,6 +153,14 @@ class NativeDebugger
 
   end
 
+  def print_delimiter
+
+  end
+
+  def check_delimiter(line)
+
+  end
+
   def switch_to_thread
 
   end
@@ -150,7 +190,7 @@ class NativeDebugger
   end
 
   def load_debugger
-    execute "call rb_eval_string_protect(\"require '#{@debugger_loader_path}'; load_debugger(#{@gems_to_include.gsub("\"", "'")}, #{@argv.gsub("\"", "'")})\", (int *)0)"
+
   end
 
   def exit
@@ -179,7 +219,6 @@ class LLDB < NativeDebugger
     info_threads = (execute 'thread list').split("\n")
     info_threads.each do |thread_info|
       next unless thread_info =~ /[\s*]*thread\s#\d+.*/
-      $stdout.puts "thread_info: #{thread_info}"
       is_main = thread_info[0] == '*'
       thread_num = thread_info.sub(/[\s*]*thread\s#/, '').sub(/:\s.*$/, '').to_i
       thread = ProcessThread.new(thread_num, is_main, thread_info, self)
@@ -203,10 +242,22 @@ class LLDB < NativeDebugger
   def call_start_attach
     super()
     execute "expr (void *) dlopen(\"#{@path_to_attach}\", 2)"
-    execute 'call start_attach()'
+    execute 'expr (int) start_attach()'
     set_tbreak(@tbreak)
   end
 
+  def print_delimiter
+    @pipe.puts "script print \"#{@delimiter}\""
+  end
+
+  def check_delimiter(line)
+    line =~ /#{@delimiter}$/
+  end
+
+  def load_debugger
+    execute "expr (VALUE) #{@eval_string}"
+  end
+
   def to_s
     'lldb'
   end
@@ -257,6 +308,18 @@ class GDB < NativeDebugger
     set_tbreak(@tbreak)
   end
 
+  def print_delimiter
+    @pipe.puts "print \"#{@delimiter}\""
+  end
+
+  def check_delimiter(line)
+    line =~ /\$\d+\s=\s"#{@delimiter}"/
+  end
+
+  def load_debugger
+    execute "call #{@eval_string}"
+  end
+
   def to_s
     'gdb'
   end
@@ -317,15 +380,21 @@ class ProcessThread
 end
 
 def command_exists(command)
+  checking_command = "checking command #{command} for existence\n"
   `command -v #{command} >/dev/null 2>&1 || { exit 1; }`
+  if $?.exitstatus != 0
+    DebugPrinter.print_debug("#{checking_command}command does not exist.")
+  else
+    DebugPrinter.print_debug("#{checking_command}command does exist.")
+  end
   $?.exitstatus == 0
 end
 
 def choose_debugger(ruby_path, pid, gems_to_include, debugger_loader_path, argv)
-  if command_exists('gdb')
-    debugger = GDB.new(ruby_path, pid, '-nh -nx', gems_to_include, debugger_loader_path, argv)
-  elsif command_exists('lldb')
+  if command_exists('lldb')
     debugger = LLDB.new(ruby_path, pid, '--no-lldbinit', gems_to_include, debugger_loader_path, argv)
+  elsif command_exists('gdb')
+    debugger = GDB.new(ruby_path, pid, '-nh -nx', gems_to_include, debugger_loader_path, argv)
   else
     raise 'Neither gdb nor lldb was found. Aborting.'
   end
@@ -348,6 +417,7 @@ debugger.attach_to_process
 debugger.set_flags
 
 if options.uid
+  DebugPrinter.print_debug("changing current uid from #{Process.uid} to #{options.uid}")
   Process::Sys.setuid(options.uid.to_i)
 end