Re: Style question: Should one check for NULL pointers?

[H. Peter Anvin]

Followup to:  <[e-mail]>
By author:    Dennis Bliefernicht <[e-mail]>
In newsgroup: linux.dev.kernel
> 
> The problem is IMHO code where some pretty fragile things are handled, 
> especially file systems. I'd say: DO the paranoia checks if some fragile 
> things are involved like key structures of the file system that can take 
> _permanent_ damage. If you check for a NULL pointer you still have the 
> chance to properly leave the system in a consistent state and no user 
> will be happy if his filesystem goes messy just because someone saved a 
> check to have nicer code, even if the original of the NULL pointer 
> wasn't his fault, even if it's a developing version. So if the check 
> isn't a total performace disaster, do it whenever permanent damage could 
> occur.
> 

Actually, you have it somewhat backwards.

In most cases, checking for NULL pointers (and returning an error
whatnot) is actually *more* likely to cause permanent damage than
having the kernel bomb out.  At least with the kernel bombing out you
won't keep grinding on a filesystem for which your kernel
datastructures are bad.  This is *IMPORTANT*.

	-hpa
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