[boost] [filesystem] Some comments

From: Martin Adrian (adrianm_at_[hidden])
Date: 2006-03-10 02:27:45

1. The exception specifications are not clear
- All predicates (exists, is_*) will throw on errors but you need to look into 
the status functions to see it.
- What happens if an error occurs while iteratoring a directory or when the 
recursive iterator can't descend into a sub-folder.

2. Why not include the system_error code in the file_status object?

If you want to avoid exceptions with the currenct code you need to write code 
like:

system_error_code ec;
file_status f(status(p, ec));

if (exists(f) && is_directory(f))
  ..
else if (status_known(f))
  cout << "path is not a directory";
else
  cout << system_error_message(ec); // can't find this function in the TR2

and

// I don't care what the problem is.
system_error_code ec;
if (is_regular(status(p, ec)))
  ...

Which is kind of messy since the ec and f can't be scoped. It also seem 
strange that you need to define a system_error_code variable just to avoid 
exceptions. 

With a file_status object defined as

struct file_status {
  explicit file_status(file_type v = status_unknown, system_error_code e = 0);
  file_type type() const;
  system_error_code error_code() const;
  std::string system_error_message() const;
  operator safe_bool() const { return ec == 0; }
};

the code can be written as:

if (file_status f(p, std::nothrow_t))
  if (exists(f) && is_directory(f))
    ...
  else
    cout << "Path is not a directory";
else
  cout << f.system_error_message();

and

if (is_regular(status(p, std::nothrow_t)))
  ...

3. Why not differentiate storage type and interface type in the basic_path 
class?