[Rd] on.exit(par(old.par)) warnings

[Paul Gilbert]

I often use something like

  old.par <- par(set someting)
  on.exit(par(old.par))

but in R 1.7.0. I now get warnings:               
          
> old.par <- par()
> par(old.par)
Warning messages: 
1: parameter "cin" can't be set in: par(args) 
2: parameter "cra" can't be set in: par(args) 
3: parameter "csi" can't be set in: par(args) 
4: parameter "cxy" can't be set in: par(args) 
5: parameter "din" can't be set in: par(args) 
6: gamma cannot be modified on this device in: par(args) 

Is this a mistake or a new feature? If it is a new feature, is there a simple
way to avoid the warnings?

Thanks,
Paul Gilbert