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From: Beman Dawes (bdawes_at_[hidden])
Date: 2005-04-06 19:53:13

"Martin" <adrianm_at_[hidden]> wrote in message
>> To me, an io error does imply some kind of failure, and a serious one at
>> that. Remember that errors reported by the system API call (stat() or
>> similar) have been analyzed, and those that clearly indicate existance or
>> not are not treated as errors. What is left are error codes that
>> represent
>> either hard errors, or conditions which are ambiguous as to the true
>> status.
> I agree partly but there are 2 cases here.
> 1. The is_x are used as filter.
> Since there is no filtering directory_iterator available you need to use
> the
> is_x function to the filtering. In many cases you just want to iterate
> over
> existing accesible files and/or directories, follow or ignore links. In
> these
> cases a throw is an inconvenience since it complicates the code without
> any
> gain.

I agree to the extent that some of the cases when the current implementation
throws can be eliminated. For example, is_directory() can safely be changed
to return false rather than throwing in the case of a non-existant path.
(And we would add a similar is_path()). But I just can't convince myself
that silently swallowing an I/O error would be safe And given the plan to
add a status() function which can provide error swallowing behavior, a
programmer can get that behavior if really, really, required.

> 2. The is_x functions are used to verify user input/configuration or
> program
> logic follows different paths depending on result of is_x functions.
> In this context I fully agree that io errors should throw an exception.
> One solution is to keep the current throwing is_x function and add
> filtering
> capabilities to director_iterator (e.g. itr->is_directory() or itr =
> directory_iterator(path, files_only)). At least on Win32 this should be
> easy
> since the status is directly availble from the findfirst/findnext
> functions.

We really do need some form of directory iteration filtering. But I really
want to finish the i18n changes (including those mentioned above) before
working on that.



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