* intended use of "safe"?
@ 2011-08-11 17:14 Ben Pfaff
2011-08-12 17:47 ` Christopher Li
0 siblings, 1 reply; 3+ messages in thread
From: Ben Pfaff @ 2011-08-11 17:14 UTC (permalink / raw)
To: linux-sparse
It looks like the sparse "safe" attribute warns about use of
"safe" values as conditional expressions. It's not obvious to me
when I would find that useful.
What is the intended use of the sparse "safe" attribute? I do
not see any uses of it in Linux (although there is a __safe macro
for it). I don't see any documentation for it either.
Thanks,
Ben.
--
Ben Pfaff
http://benpfaff.org
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: intended use of "safe"?
2011-08-11 17:14 intended use of "safe"? Ben Pfaff
@ 2011-08-12 17:47 ` Christopher Li
2011-08-12 17:58 ` Josh Triplett
0 siblings, 1 reply; 3+ messages in thread
From: Christopher Li @ 2011-08-12 17:47 UTC (permalink / raw)
To: blp; +Cc: linux-sparse
On Thu, Aug 11, 2011 at 10:14 AM, Ben Pfaff <blp@cs.stanford.edu> wrote:
> What is the intended use of the sparse "safe" attribute? I do
> not see any uses of it in Linux (although there is a __safe macro
> for it). I don't see any documentation for it either.
I don't know much about the safe attribute either. I find out the
commit which introduce the safe attribute by "git blame".
If a pointer is never NULL, there is not need to test the pointer.
Chris
commit 98f14350c26518f0f5c45632d145a218d468d8b8
Author: Linus Torvalds <torvalds@ppc970.osdl.org>
Date: Fri Apr 16 18:19:30 2004 -0700
Introduce "safe" pointer expressions.
These are defined to never be NULL or nontrapping, and could
help code generation, but right now only cause a warning if
they are tested in a conditional.
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^ permalink raw reply [flat|nested] 3+ messages in thread* Re: intended use of "safe"?
2011-08-12 17:47 ` Christopher Li
@ 2011-08-12 17:58 ` Josh Triplett
0 siblings, 0 replies; 3+ messages in thread
From: Josh Triplett @ 2011-08-12 17:58 UTC (permalink / raw)
To: Christopher Li; +Cc: blp, linux-sparse
On Fri, Aug 12, 2011 at 10:47:11AM -0700, Christopher Li wrote:
> On Thu, Aug 11, 2011 at 10:14 AM, Ben Pfaff <blp@cs.stanford.edu> wrote:
> > What is the intended use of the sparse "safe" attribute? I do
> > not see any uses of it in Linux (although there is a __safe macro
> > for it). I don't see any documentation for it either.
>
> I don't know much about the safe attribute either. I find out the
> commit which introduce the safe attribute by "git blame".
>
> If a pointer is never NULL, there is not need to test the pointer.
>
> Chris
>
> commit 98f14350c26518f0f5c45632d145a218d468d8b8
> Author: Linus Torvalds <torvalds@ppc970.osdl.org>
> Date: Fri Apr 16 18:19:30 2004 -0700
>
> Introduce "safe" pointer expressions.
>
> These are defined to never be NULL or nontrapping, and could
> help code generation, but right now only cause a warning if
> they are tested in a conditional.
That does actually seem useful. The Linux kernel has various structures
with pointers that should never be NULL, and documenting that in a
compiler-visible way seems like a feature.
- Josh Triplett
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