Re: [boost] boost::filesystem - directory_iteratormakesoptimizationhard

From: Peter Dimov (pdimov_at_[hidden])
Date: 2005-06-13 15:09:15

Beman Dawes wrote:

> The "too similar" problem with overloading predicate functions on
> directory_iterator is that two very similar calls have different
> behavior:
>     if ( is_directory( *itr ) ) // uses current status
>
>     if ( is_directory( itr ) ) // uses cached status, which may be very 
> stale
>
> That looks like a race-condition trap for unwary users.

I could argue that the second form is less "trappy" for unwary users, 
actually, because all is_directory( itr ) calls will always yield the same 
value (and exists(itr) will never yield false for an enumerated item). This 
comes into play in situations like:

void f( itr )
{
    if( is_directory(itr) )
    {
        g( itr );
    }
    else
    {
        h( itr );
    }
}

void g( itr )
{
    if( is_directory(itr) )
    {
        // ...
    }
    else
    {
        // ...
    }
}