At 12:55 PM 3/9/2004, Peter Dimov wrote:
Walter Landry wrote:
Beman Dawes <bdawes@acm.org> wrote:
At 01:55 AM 3/9/2004, Vladimir Prus wrote:
After all, caller only cares if directory exists, if it was created by >another thread it's ok.
That's an interesting thought. Of course, it might not be another thread but rather another process that created the directory, and that could be a sign of real trouble.
Exactly. Normally people use lock-files, but I personally have a use for lock-directories. If boost::filesystem starts swallowing errors, it makes it more difficult to achieve that.
It doesn't have to swallow errors. It can simply signal some errors via exceptions and some errors via return values.
I would say that people who don't care whether a directory is created should just catch the exception themselves. Alternately, you could generalize make_directory to take an extra, optional argument that specifies whether to throw if the directory already exists. Of course, it should always throw if the error is something different (e.g. if the parent directory doesn't exist).
This almost goes without saying.
create_directory(path p)
post: p exists and is a directory
If the postcondition cannot be satisfied, create_directory _must_ throw. But if p already exists and is a directory, the postcondition already holds, so we are free to report the "error" via a different mechanism (COM, for example, has a conventional "alternate success code" S_FALSE for such situations).
We have a similar case with remove(), which is reported by remove() returning a bool indicating if it actually removed anything. It would be quite consistent for create_directory() to return a bool indicating if it actually had to create the directory. --Beman