Source/JavaScriptCore/Scripts/resolve-asm-file-conflicts.rb - WebKit - Git at Google

 #!/usr/bin/env ruby

 # Copyright (C) 2020 Igalia S. L.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
 # are met:
 # 1. Redistributions of source code must retain the above copyright
 #    notice, this list of conditions and the following disclaimer.
 # 2. Redistributions in binary form must reproduce the above copyright
 #    notice, this list of conditions and the following disclaimer in the
 #    documentation and/or other materials provided with the distribution.
 #
 # THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 # THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 # PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 # BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 # INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 # THE POSSIBILITY OF SUCH DAMAGE.

 # Resolve conflicts in `.file` directives in assembler files. Those
 # may result from inline asm statements which themselves have `.file`
 # directives. As the inline asm has no idea what the next free file
 # number is, it'll generally have its own numbering. To get things to
 # work we have to
 # 1. remap conflicting file numbers
 # 2. change `.loc` directives to reference the appropriate file number.
 #
 # To be able to do that, we need some concept of "scope", i.e. which
 # set of files a given `.loc` directive refers to. We get that by
 # tracking the #APP/#NOAPP directives that the compiler emits when it
 # switch to/from inline asm.
 #
 # In effect, we convert
 #     .file 1 "foo"
 #     #APP
 #     .file 1 "bar"
 #     .file 2 "foo"
 #     .loc 1, X
 #     #NOAPP
 #     .loc 1, Y
 # to
 #     .file 1 "foo"
 #     #APP
 #     .file 2 "bar"
 #     .file 1 "foo"
 #     .loc 2, X
 #     #NOAPP
 #     .loc 1, Y

 require 'pathname'
 require 'stringio'
 require 'strscan'

 ParseResultSuccess = Struct.new(:str)
 ParseResultError = Struct.new(:error)

 # Parses the single string literal following a .file assembler directive
 class FileDirectiveArgScanner
   def initialize(s)
     @s = StringScanner.new(s)
   end
   def parse
     @s.skip(/\s*/)

     # We require at least one string literal
     ret = parse_string_literal
     if ret.respond_to?(:error)
       return ret
     end

     @s.skip(/\s*/)
     if not @s.eos?
       return ParseResultError.new("Expected end of line after #{ret.str}")
     end
     return ParseResultSuccess.new(ret.str)
   end
   def parse_string_literal
     if @s.scan(/"/).nil?
       err = "Expected string literal at `#{@s.string}` (pos #{@s.pos})"
       return ParseResultError.new(err)
     end
     parse_until_end_of_string_literal
   end
   def parse_until_end_of_string_literal
     start_pos = @s.pos
     while true
       # Search for our special characters
       @s.skip(/[^"\\]+/)
       if @s.scan(/\\/)
         if @s.scan(/\\/)
           # When we see '\\', consume both characters so that the
           # second '\' will not be treated as an escape char.
           next
         elsif @s.scan(/"/)
           # For '\"', consume both characters so that the '"' will not
           # terminate the string.
           next
         end
         next
       elsif @s.scan(/"/)
         # '"' without a preceeding '\'; terminate the literal.
         # We're already past the '"', so the literal ends at -2
         # characters.
         return ParseResultSuccess.new(@s.string[start_pos..(@s.pos - 2)])
       elsif @s.eos?
         err = "Unterminated string literal (starting at pos #{start_pos} in #{@s.string}"
         return ParseResultError.new(err)
       end
       raise "Internal error (#{@s.inspect})"
     end
   end
 end

 def test(outf, str, res)
   pr = FileDirectiveArgScanner.new(str).parse
   if res.is_a?(Array)
     if pr.respond_to?(:error)
       outf.puts("Parse result is `#{pr.error}` but expected #{res}")
       return false
     end
     if pr.str != res[0]
       outf.puts("Parsed path `#{pr.str}` but expected `#{res[0]}`")
       return false
     end
     return true
   elsif res.is_a?(String)
     if pr.respond_to?(:error)
       if not pr.error.downcase.include?(res.downcase)
         err = "Error message `#{pr.error}` does not include expected substring `#{res}`"
         outf.puts(err)
         return false
       end
       return true
     end
     outf.puts("Expected error (#{res}) but got successful parse #{pr.str}")
     return false
   else
     raise "Internal error #{res.class}"
   end
 end

 def selftest
   nr_succeeded = 0
   tests = [
     # simple string
     ['"foo/bar"', ["foo/bar"]],

     ['"foo', "Unterminated string literal"],

     ['"foo\"', "Unterminated string literal"],

     # "foo\"
     ["\"foo\\\"", "Unterminated string literal"],

     # "foo\\"
     ["\"foo\\\\\"", ["foo\x5c\x5c"]],

     # Can escape '"'
     ['"foo\"bar"', ['foo\"bar']],

     # Can parse relative
     ['"foo/bar"', ['foo/bar']],

     # Can parse absolute
     ['"/bar"', ['/bar']],

     # Can parse absolute with two components
     ['"/bar/baz"', ['/bar/baz']],

     # Can detect stray token
     ['"foo" bar', "Expected end of line"],

     # Can detect stray token without whitespace
     ['"foo"bar', "Expected end of line"],

     # Will not accept clang-style .file directives
     ['"working_directory" "path"', "Expected end of line"]
   ]
   outf = StringIO.new("")
   tests.each { |str, res|
     if test(outf, str, res)
       nr_succeeded += 1
     end
   }
   if nr_succeeded != tests.size
     $stderr.puts(outf.string)
     $stderr.puts("Some self tests failed #{nr_succeeded}/#{tests.size}")
     exit(3)
   end
 end

 # Keep track of which fileno is assigned to which file path. We call
 # the fileno a 'slot'.
 class FileSlotTracker
   @@next_free = 1   # Next free global slot
   @@paths = {} # Maps path -> global slot
   def initialize(parent)
     @parent = parent
     # This maps from our own local slots (i.e. within an APP section)
     # to a global slot.
     @slot_map = {}
   end
   # We make sure that .file directives that specify the same path are
   # dedup'd, i.e. if we see
   #     .file N "/path/to/include.h"
   #     ...
   #     .file M "/path/to/include.h"
   # then the "local" N, M slots will be mapped to the same "global" slot.
   def register_path(path, slot)
     curr_slot = @@paths[path]
     if curr_slot.nil?
       # We haven't seen this file before
       if slot <= @@next_free
         # Desired file slot either clashes with an existing one, or is
         # the next one to be allocated. In either case, assign the
         # next free slot.
         assign_next_slot(path)
       else
         # Don't allow slot gaps. Technically we could handle them, but
         # they should never happen; bail now rather than papering over
         # an earlier error.
         $stderr.puts("File wants slot #{slot} but only seen #{@@next_free} so far")
         exit(2)
       end
     else
       # We've already assigned a slot for this file.
     end
     @slot_map[slot] = @@paths[path]
     if @slot_map[slot].nil?
       raise "Didn't map local slot #{slot}"
     end
   end
   # Return global slot for path
   def slot_for_path(path)
     return @@paths[path]
   end
   # Return global slot that will replace the local slot
   def remap_slot(slot)
     ret = nil
     if @slot_map.size > 0
       # If the current NO_APP segment has defined a .file, only look
       # in the current FileSlotTracker. This is the case for a
       # top-level inline asm statement.
       ret = @slot_map[slot]
     elsif not @parent.nil?
       # If the current NO_APP segment has not defined a .file, clearly
       # all .loc directives refer to files defined in the APP
       # part. This is the case for non-top-level inline asm
       # statements.
       ret = @parent.remap_slot(slot)
     end
     if ret.nil?
       raise "No global slot for #{slot}"
     end
     ret
   end
   private
   def assign_next_slot(path)
     @@paths[path] = @@next_free
     @@next_free += 1
   end
 end

 # Return sequential lines, while keeping track of whether we're in an
 # #APP or #NOAPP section.
 class AsmReader
   attr_reader :in_app
   attr_accessor :app_to_noapp, :noapp_to_app
   def initialize(f)
     @f = f
     @f.rewind
     @linenr = 0
     @in_app = false
     @last_switch = "start of file" # For error messages
   end
   def next_line
     while true
       l = @f.gets
       if l.nil?
         return l
       end
       @linenr += 1
       if /^#\s*APP\s*/.match(l)
         if @in_app
           raise "#APP on line #{@linenr} but already in #APP (#{@last_switch})"
         end
         @in_app = true
         @last_switch = @linenr
         if @noapp_to_app
           @noapp_to_app.call()
         end
       end
       if /^#\s*NO_APP\s*/.match(l)
         if not @in_app
           raise "#NOAPP on line #{@linenr} but was not in #APP (last swich at #{@last_switch})"
         end
         @in_app = false
         @last_switch = @linenr
         if @app_to_noapp
           @app_to_noapp.call()
         end
       end
       return l
     end
   end
 end

 class FileConflictResolver
   @@file_re = /^\s*[.]file\s+(?<slot>\d+)\s+(?<rest>.*)$/
   @@loc_re = /^(?<white1>\s*)[.]loc(?<white2>\s+)(?<slot>\d+)(?<rest>\s+\d+.*)$/
   def initialize(inf, outf)
     @outf = outf
     @trackers = [FileSlotTracker.new(nil)]
     @asm_reader = AsmReader.new(inf)
     # When we enter an #APP section (i.e. asm emitted from an expanded
     # inline asm statement), create a new file tracker, in effect
     # processing the .file and .loc directives in a new "namespace"
     # (as far as the file numbers are concerned). This is an array,
     # but in practice the size will either be 1 (NOAPP) or 2 (APP).
     @asm_reader.app_to_noapp = Proc.new { ||
                                           @trackers.pop
     }
     @asm_reader.noapp_to_app = Proc.new { ||
                                           @trackers.push(FileSlotTracker.new(@trackers[-1]))
     }
   end
   def run
     while true
       l = @asm_reader.next_line
       break unless l

       md = @@file_re.match(l)
       if md
         file_directive(md)
         next
       end
       md = @@loc_re.match(l)
       if md
         loc_directive(md)
         next
       end
       @outf.write(l)
       next
     end
   end
   def loc_directive(md)
     tracker = @trackers.last
     slot = tracker.remap_slot(md[:slot].to_i)
     @outf.puts("#{md[:white1]}.loc#{md[:white2]}#{slot}#{md[:rest]}")
   end
   def file_directive(md)
     tracker = @trackers.last

     pr = FileDirectiveArgScanner.new(md[:rest]).parse
     if pr.respond_to?(:error)
       $stderr.puts("Error parsing path argument to .file directive: #{pr.error}")
       exit(2)
     end

     path = pr.str
     tracker.register_path(path, md[:slot].to_i)

     slot = tracker.slot_for_path(path)
     @outf.puts("\t.file\t#{slot} #{md[:rest]}")
   end
 end

 # First, make sure our tests still pass. This only takes a fraction of
 # our runtime and ensures the tests will get run by anyone trying out
 # changes to this file.
 selftest

 if ARGV.size != 2
   $stderr.puts("Usage: #{$0} input output")
   exit(2)
 end

 inpath, outpath = ARGV.collect { |n| Pathname.new(n) }

 if not inpath.file?
   $stderr.puts("Not a regular file: `#{inpath}`")
   exit(2)
 end

 if inpath.extname.upcase != ".S"
   $stderr.puts("warning: file `#{inpath}` doesn't have a `.s` or `.S` extension. Going on anyway...")
 end

 File.open(inpath, "r") { |inf|
   File.open(outpath, "w") { |outf|
     FileConflictResolver.new(inf, outf).run
   }
 }
	#!/usr/bin/env ruby

	# Copyright (C) 2020 Igalia S. L.
	#
	# Redistribution and use in source and binary forms, with or without
	# modification, are permitted provided that the following conditions
	# are met:
	# 1. Redistributions of source code must retain the above copyright
	# notice, this list of conditions and the following disclaimer.
	# 2. Redistributions in binary form must reproduce the above copyright
	# notice, this list of conditions and the following disclaimer in the
	# documentation and/or other materials provided with the distribution.
	#
	# THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
	# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
	# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
	# BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
	# THE POSSIBILITY OF SUCH DAMAGE.

	# Resolve conflicts in `.file` directives in assembler files. Those
	# may result from inline asm statements which themselves have `.file`
	# directives. As the inline asm has no idea what the next free file
	# number is, it'll generally have its own numbering. To get things to
	# work we have to
	# 1. remap conflicting file numbers
	# 2. change `.loc` directives to reference the appropriate file number.
	#
	# To be able to do that, we need some concept of "scope", i.e. which
	# set of files a given `.loc` directive refers to. We get that by
	# tracking the #APP/#NOAPP directives that the compiler emits when it
	# switch to/from inline asm.
	#
	# In effect, we convert
	# .file 1 "foo"
	# #APP
	# .file 1 "bar"
	# .file 2 "foo"
	# .loc 1, X
	# #NOAPP
	# .loc 1, Y
	# to
	# .file 1 "foo"
	# #APP
	# .file 2 "bar"
	# .file 1 "foo"
	# .loc 2, X
	# #NOAPP
	# .loc 1, Y

	require 'pathname'
	require 'stringio'
	require 'strscan'

	ParseResultSuccess = Struct.new(:str)
	ParseResultError = Struct.new(:error)

	# Parses the single string literal following a .file assembler directive
	class FileDirectiveArgScanner
	def initialize(s)
	@s = StringScanner.new(s)
	end
	def parse
	@s.skip(/\s*/)

	# We require at least one string literal
	ret = parse_string_literal
	if ret.respond_to?(:error)
	return ret
	end

	@s.skip(/\s*/)
	if not @s.eos?
	return ParseResultError.new("Expected end of line after #{ret.str}")
	end
	return ParseResultSuccess.new(ret.str)
	end
	def parse_string_literal
	if @s.scan(/"/).nil?
	err = "Expected string literal at `#{@s.string}` (pos #{@s.pos})"
	return ParseResultError.new(err)
	end
	parse_until_end_of_string_literal
	end
	def parse_until_end_of_string_literal
	start_pos = @s.pos
	while true
	# Search for our special characters
	@s.skip(/[^"\\]+/)
	if @s.scan(/\\/)
	if @s.scan(/\\/)
	# When we see '\\', consume both characters so that the
	# second '\' will not be treated as an escape char.
	next
	elsif @s.scan(/"/)
	# For '\"', consume both characters so that the '"' will not
	# terminate the string.
	next
	end
	next
	elsif @s.scan(/"/)
	# '"' without a preceeding '\'; terminate the literal.
	# We're already past the '"', so the literal ends at -2
	# characters.
	return ParseResultSuccess.new(@s.string[start_pos..(@s.pos - 2)])
	elsif @s.eos?
	err = "Unterminated string literal (starting at pos #{start_pos} in #{@s.string}"
	return ParseResultError.new(err)
	end
	raise "Internal error (#{@s.inspect})"
	end
	end
	end

	def test(outf, str, res)
	pr = FileDirectiveArgScanner.new(str).parse
	if res.is_a?(Array)
	if pr.respond_to?(:error)
	outf.puts("Parse result is `#{pr.error}` but expected #{res}")
	return false
	end
	if pr.str != res[0]
	outf.puts("Parsed path `#{pr.str}` but expected `#{res[0]}`")
	return false
	end
	return true
	elsif res.is_a?(String)
	if pr.respond_to?(:error)
	if not pr.error.downcase.include?(res.downcase)
	err = "Error message `#{pr.error}` does not include expected substring `#{res}`"
	outf.puts(err)
	return false
	end
	return true
	end
	outf.puts("Expected error (#{res}) but got successful parse #{pr.str}")
	return false
	else
	raise "Internal error #{res.class}"
	end
	end

	def selftest
	nr_succeeded = 0
	tests = [
	# simple string
	['"foo/bar"', ["foo/bar"]],

	['"foo', "Unterminated string literal"],

	['"foo\"', "Unterminated string literal"],

	# "foo\"
	["\"foo\\\"", "Unterminated string literal"],

	# "foo\\"
	["\"foo\\\\\"", ["foo\x5c\x5c"]],

	# Can escape '"'
	['"foo\"bar"', ['foo\"bar']],

	# Can parse relative
	['"foo/bar"', ['foo/bar']],

	# Can parse absolute
	['"/bar"', ['/bar']],

	# Can parse absolute with two components
	['"/bar/baz"', ['/bar/baz']],

	# Can detect stray token
	['"foo" bar', "Expected end of line"],

	# Can detect stray token without whitespace
	['"foo"bar', "Expected end of line"],

	# Will not accept clang-style .file directives
	['"working_directory" "path"', "Expected end of line"]
	]
	outf = StringIO.new("")
	tests.each { \|str, res\|
	if test(outf, str, res)
	nr_succeeded += 1
	end
	}
	if nr_succeeded != tests.size
	$stderr.puts(outf.string)
	$stderr.puts("Some self tests failed #{nr_succeeded}/#{tests.size}")
	exit(3)
	end
	end

	# Keep track of which fileno is assigned to which file path. We call
	# the fileno a 'slot'.
	class FileSlotTracker
	@@next_free = 1 # Next free global slot
	@@paths = {} # Maps path -> global slot
	def initialize(parent)
	@parent = parent
	# This maps from our own local slots (i.e. within an APP section)
	# to a global slot.
	@slot_map = {}
	end
	# We make sure that .file directives that specify the same path are
	# dedup'd, i.e. if we see
	# .file N "/path/to/include.h"
	# ...
	# .file M "/path/to/include.h"
	# then the "local" N, M slots will be mapped to the same "global" slot.
	def register_path(path, slot)
	curr_slot = @@paths[path]
	if curr_slot.nil?
	# We haven't seen this file before
	if slot <= @@next_free
	# Desired file slot either clashes with an existing one, or is
	# the next one to be allocated. In either case, assign the
	# next free slot.
	assign_next_slot(path)
	else
	# Don't allow slot gaps. Technically we could handle them, but
	# they should never happen; bail now rather than papering over
	# an earlier error.
	$stderr.puts("File wants slot #{slot} but only seen #{@@next_free} so far")
	exit(2)
	end
	else
	# We've already assigned a slot for this file.
	end
	@slot_map[slot] = @@paths[path]
	if @slot_map[slot].nil?
	raise "Didn't map local slot #{slot}"
	end
	end
	# Return global slot for path
	def slot_for_path(path)
	return @@paths[path]
	end
	# Return global slot that will replace the local slot
	def remap_slot(slot)
	ret = nil
	if @slot_map.size > 0
	# If the current NO_APP segment has defined a .file, only look
	# in the current FileSlotTracker. This is the case for a
	# top-level inline asm statement.
	ret = @slot_map[slot]
	elsif not @parent.nil?
	# If the current NO_APP segment has not defined a .file, clearly
	# all .loc directives refer to files defined in the APP
	# part. This is the case for non-top-level inline asm
	# statements.
	ret = @parent.remap_slot(slot)
	end
	if ret.nil?
	raise "No global slot for #{slot}"
	end
	ret
	end
	private
	def assign_next_slot(path)
	@@paths[path] = @@next_free
	@@next_free += 1
	end
	end

	# Return sequential lines, while keeping track of whether we're in an
	# #APP or #NOAPP section.
	class AsmReader
	attr_reader :in_app
	attr_accessor :app_to_noapp, :noapp_to_app
	def initialize(f)
	@f = f
	@f.rewind
	@linenr = 0
	@in_app = false
	@last_switch = "start of file" # For error messages
	end
	def next_line
	while true
	l = @f.gets
	if l.nil?
	return l
	end
	@linenr += 1
	if /^#\sAPP\s/.match(l)
	if @in_app
	raise "#APP on line #{@linenr} but already in #APP (#{@last_switch})"
	end
	@in_app = true
	@last_switch = @linenr
	if @noapp_to_app
	@noapp_to_app.call()
	end
	end
	if /^#\sNO_APP\s/.match(l)
	if not @in_app
	raise "#NOAPP on line #{@linenr} but was not in #APP (last swich at #{@last_switch})"
	end
	@in_app = false
	@last_switch = @linenr
	if @app_to_noapp
	@app_to_noapp.call()
	end
	end
	return l
	end
	end
	end

	class FileConflictResolver
	@@file_re = /^\s[.]file\s+(?<slot>\d+)\s+(?<rest>.)$/
	@@loc_re = /^(?<white1>\s)[.]loc(?<white2>\s+)(?<slot>\d+)(?<rest>\s+\d+.)$/
	def initialize(inf, outf)
	@outf = outf
	@trackers = [FileSlotTracker.new(nil)]
	@asm_reader = AsmReader.new(inf)
	# When we enter an #APP section (i.e. asm emitted from an expanded
	# inline asm statement), create a new file tracker, in effect
	# processing the .file and .loc directives in a new "namespace"
	# (as far as the file numbers are concerned). This is an array,
	# but in practice the size will either be 1 (NOAPP) or 2 (APP).
	@asm_reader.app_to_noapp = Proc.new { \|\|
	@trackers.pop
	}
	@asm_reader.noapp_to_app = Proc.new { \|\|
	@trackers.push(FileSlotTracker.new(@trackers[-1]))
	}
	end
	def run
	while true
	l = @asm_reader.next_line
	break unless l

	md = @@file_re.match(l)
	if md
	file_directive(md)
	next
	end
	md = @@loc_re.match(l)
	if md
	loc_directive(md)
	next
	end
	@outf.write(l)
	next
	end
	end
	def loc_directive(md)
	tracker = @trackers.last
	slot = tracker.remap_slot(md[:slot].to_i)
	@outf.puts("#{md[:white1]}.loc#{md[:white2]}#{slot}#{md[:rest]}")
	end
	def file_directive(md)
	tracker = @trackers.last

	pr = FileDirectiveArgScanner.new(md[:rest]).parse
	if pr.respond_to?(:error)
	$stderr.puts("Error parsing path argument to .file directive: #{pr.error}")
	exit(2)
	end

	path = pr.str
	tracker.register_path(path, md[:slot].to_i)

	slot = tracker.slot_for_path(path)
	@outf.puts("\t.file\t#{slot} #{md[:rest]}")
	end
	end

	# First, make sure our tests still pass. This only takes a fraction of
	# our runtime and ensures the tests will get run by anyone trying out
	# changes to this file.
	selftest

	if ARGV.size != 2
	$stderr.puts("Usage: #{$0} input output")
	exit(2)
	end

	inpath, outpath = ARGV.collect { \|n\| Pathname.new(n) }

	if not inpath.file?
	$stderr.puts("Not a regular file: `#{inpath}`")
	exit(2)
	end

	if inpath.extname.upcase != ".S"
	$stderr.puts("warning: file `#{inpath}` doesn't have a `.s` or `.S` extension. Going on anyway...")
	end

	File.open(inpath, "r") { \|inf\|
	File.open(outpath, "w") { \|outf\|
	FileConflictResolver.new(inf, outf).run
	}
	}