On 6/26/22 02:58, Luc Van Oostenryck wrote:
On Sat, Jun 25, 2022 at 05:44:54PM -0700, Bart Van Assche wrote:
On 6/25/22 02:23, Christoph Hellwig wrote:
Yeah, that is a bit of a mess. Rasmus, Steven - any good idea how
we can make the trace even macros fit for sparse? Maybe just drop the
is_signed_type check for __CHECKER__ ?
I would strongly advise against this:
-) the macro is sued elsewhere too (for overflow checking)
-) sparse wouldn't check anymore the same code as the one seen by the
compiler
What about I would add to sparse something to strip away the bitwise/
recover the underlying type? Something like __unbitwiseof() or
__underlying_typeof() (some better name is needed)?
Implementing directly what's needed here, something like __is_signed_type()
would be possible too but is a bit too specialized and so much less useful.
Another question is how to keep the non-sparse build working. Does
anyone want to comment on the following alternatives or propose another
alternative?
(1) sparse implements __strip_bitwise as a macro.
(in compiler.h)
#ifndef __strip_bitwise
#define __strip_bitwise(type) type
#endif
(in trace_events.h)
#define is_signed_type(type) ((__strip_bitwise(type))(-1) < (__strip_bitwise(type))1)
(2) sparse implements __strip_bitwise as an operator that works on types.
#ifdef __CHECKER__
#define is_signed_type(type) ((__strip_bitwise(type))(-1) < (__strip_bitwise(type))1)
#else
#define is_signed_type(type) (((type)(-1)) < (type)1)
#endif
(1) would work better than (2) for kernel developers who are using a
version of sparse that does not support __strip_bitwise().
Thanks,
Bart.
