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From: Arnd Bergmann <arnd@arndb.de>
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Date: Fri, 22 Jul 2016 21:12:52 +0200
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Cc: Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [Ksummit-discuss] [CORE TOPIC] More useful types in the linux
	kernel
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On Friday, July 22, 2016 3:57:40 PM CEST Hannes Reinecke wrote:
> On 07/22/2016 08:14 AM, Julia Lawall wrote:
> > On Fri, 22 Jul 2016, Hannes Reinecke wrote:
> >>
> >> Actually that's one thing on my long-term to-do list: stricter range
> >> checking for kernel functions.
> >> enums are an obvious way to address that,

I think smatch has some useful checks in that area, and using a gcc
plugin to have a similar implementation could help do the checks
by default (if there are not too many false positives). 

> > In C, enums are ints.  Is there a Gcc option that checks them?  For
> > example, the following program compiles fine with -Wall:
> > 
> > enum one {ONE=1, TWO=2, THREE=3};
> > enum two {ONEX=7, TWOX=8, THREEX=9};
> > 
> > int f (int x) {
> >   enum one o = ONE;
> >   enum two t = THREEX;
> >   if (x) o = t; else t = o;
> >   return 0;
> > }
> > 
> From what I know GCC only checks enums if they are used in a switch()
> statement. Other types are not checked.

I think a common bug is having a function that takes an enum argument
type but that is called with integer argument, or a different
enum. This might even be something that could be added to a gcc
version by default.

	Arnd