[fpc-pascal] RE: findfirst and findnext on non accessible files

[Michael Van Canneyt]

On Wed, 28 Jun 2006, Marc Santhoff wrote:

> Am Mittwoch, den 28.06.2006, 12:17 -0500 schrieb Jeff Pohlmeyer:
> > If I remember correctly, the DOS FindFirst/Next only handles
> > shortstring-sized path names.
> 
> If possible at all I will not use DOS unit.
> 
> > Another "quirk" about using FindNext on Unix is that a
> > symlink to a directory sets the faDirectory flag, and if it
> > happens to be a circular symlink,  I don't know of any
> > way tell if it is safe to recurse into it without using fpStat
> > or something like it. FindNext will eventually give up after
> > several loops, but that doesn't seem like a very
> > elegant way to handle the situation.
> 
> This should be no problem in principle, since the unix syscalls detect
> this state and fail (according to Stevens[1]). But relying on the system
> working properly is no good policy ...

IMHO:
On the contrary. If you can't trust the system, then what can you trust ?

> What I don't understand is why the var "errno" is not set or it's value
> is destroyed before Findfirst/-Next return. Does this value has to be
> set explicitely by using fpseterrno()? It returns always -1 in case of
> permission denied.

You should not ever rely on SysUtils setting errno. 
Errno is a variable used in the Unix subsystem. 
It is only valid to check errno when directly executing calls from the 
baseunix,unix calls.

SysUtils calls may or may not destroy this value, but you should not rely on this.

Michael.