Missing Errnos - Crystal lang

missing_errnos.cr

# Run this using
#     touch sample.txt
#     crystal run missing_errnos.cr -- sample.txt
# Above command fails to compile if we uncomment the line 39
lib LibXAttr
  {% if flag?(:linux) %}
    fun getxattr(path : LibC::Char*, name : LibC::Char*, value : LibC::Char*, size : LibC::SizeT) : LibC::Int
  {% end %}
  {% if flag?(:darwin) %}
    fun getxattr(path : LibC::Char*, name : LibC::Char*, value : LibC::Char*, size : LibC::SizeT, position : LibC::UInt32T, options : LibC::Int) : LibC::Int
  {% end %}
end

def getxattr(path, key, value, size)
  {% if flag?(:linux) %}
    LibXAttr.getxattr(path, key, value, size)
  {% end %}
  {% if flag?(:darwin) %}
    LibXAttr.getxattr(path, key, value, size, 0, 0)
  {% end %}
end


def raise_error()
  raise IO::Error.from_errno("Xattr Error")
end

begin
  size = getxattr(ARGV[0], "user.nonexisting", nil, 0)
  raise_error() if size == -1

  ptr = Slice(LibC::Char).new(size)
  res = getxattr(ARGV[0], "user.nonexisting", ptr, size)
  raise_error() if res == -1

  puts String.new(ptr)
rescue ex: IO::Error
  # Uncommenting below line raises error on Mac
  # if ex.os_error == Errno::ENODATA || ex.os_error == Errno::ENOATTR
  if ex.os_error == Errno::ENODATA
    puts "Xattr not found"
  end
end