Re: [boost] Filesystem Library --- exceptions

From: Beman Dawes (bdawes_at_[hidden])
Date: 2002-09-23 14:12:42

At 04:35 AM 9/23/2002, Vladimir Prus wrote:

Volodya,

 >I'm starting to think that exceptions thrown by the filesystem library
 >are too coarse grained --- there is many types of errors, all of them
 >result in the same class thrown, and the only way to tell what happened
 >is to look at 'what()' results.
 >
 >To be concrete, suppose I call 'rename' and it throws. There are at
 >least to reasons of failure: (1) source file does not exist and (2)
 >source and destination are on different drives/filesystems. In the
 >second case I'd want to call 'copy', followed by 'remove'. However, how
 >can I detect that the second case caused the error?

Notice that filesystem_error has a public member error() which returns the 
system error code if there is one.  But I don't think that solves the 
problem you are talking about since it isn't a portable return value. (The 
design was inherited from the old dir_it library, IIRC.)

Digression: Most of the filesystem function Throws clauses mention one or 
two conditions which always cause exceptions.  But there are a bunch of 
other operating system specific conditions ("don't have the right 
permissions", "O/S is out of some resource", etc.) which can also cause 
exceptions.

Maybe we could identify a few of the very most common conditions ("file not 
found"), and supply exceptions derived from filesystem_error for 
those.  Anything else would just throw filesystem_error.

Would that solve the problem?

--Beman