Re: sasc re-write

[Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>]

:On Mon(17)/Jan/05 - , Diane Bruce wrote:
:> On Mon, Jan 17, 2005 at 09:24:53AM +0100, Simon 'corecode' Schubert wrote:
:> > hey, just a few comments
:> >
:> ...
:> 
:> And a nit...
:> 
:> > >+        val = strtol(str, &ep, 10);
:> > >+        if (errno)
:> > >+                err(1, "strtol failed: %s", str);
:> 
:> 
:> I'd not attempt to use errno as a boolean, I'd do:
:> 
:> if (errno != 0)
:> 	...
:> 
:> Especially as later on you do:
:> 
:> >+      if (ioctl(fd, asc_setting, &asc_value) < 0)
:
:I disagree. errno is normally used as boolean.
:
:> 
:> > you don't reset errno to 0, so this might be not working. reading the
:> > man page it might be needed :/
:> 
:> Indeed it would be.
:> 
:> - Diane.
:
:-- 
:- Liam J. Foy
:<liamfoy@xxxxxxxxxxxxx>

    Diane is right.  errno is only modified when something fails, which
    means that it tends to 'accumulate' a non-zero value even if the last
    50 system calls succeeded.

    You are only supposed to check errno if a particular operation fails.
    e.g. if (lseek(...) < 0) { ... check errno }

    strtol() is one of those rare functions where the only safe way to 
    check errno is to clear it prior to calling the function because the
    error return value may also represent a non-error value.

    In anycase, I recommend not bothering with errno at all for strtol().
    Just check that the returned value is in a reasonable range.

					-Matt
					Matthew Dillon 
					<dillon@xxxxxxxxxxxxx>