Messages in this thread | | | Date | Thu, 22 Mar 2012 16:09:44 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 00/16] mm: prepare for converting vm->vm_flags to 64-bit |
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On Fri, 23 Mar 2012 02:52:05 +0400 Konstantin Khlebnikov <khlebnikov@openvz.org> wrote:
> >> Is this ok? > > > > Yes. > > > > The thing about __nocast is that it's so *very* very easy to lose it. > > For example, do this: > > > > typedef long __nocast long_t; > > > > int main(long_t a) > > { > > return a; > > } > > > > and you get the (expected) warning. > > > > HOWEVER. Now do "return a+1" instead, and the warning goes away. Why? > > Because the expression ends up having just the type "long", because > > the "a" mixed happily with the "1" (that was cast from 'int' to 'long' > > by the normal C type rules). > > > > That is arguably a bug, but this kind of thing really wasn't what > > __nocast was designed for. The __nocast design ended up being too > > weak, though, and we hardly use it in the kernel. > > > > Thanks. Looks like "__nocast" totally undocumented. > It would be nice to add something about this into Documentation/sparse.txt
Yup, Chris has added this to his todo list (thanks!).
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