sparse warnings in overflow.h

sparse warnings in overflow.h

[Miroslav Benes]

Hi Kees,

sparse (make C=1) gives me this warnings today...

./include/linux/overflow.h:254:13: error: undefined identifier '__builtin_mul_overflow'
./include/linux/overflow.h:254:13: error: incorrect type in conditional
./include/linux/overflow.h:254:13:    got void
./include/linux/overflow.h:256:13: error: undefined identifier '__builtin_add_overflow'
./include/linux/overflow.h:256:13: error: incorrect type in conditional
./include/linux/overflow.h:256:13:    got void

This hunk obviously fixes it, but I'm really not sure if it is a proper 
fix.

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index f1a7492a5cc8..15e55b89e952 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -344,6 +344,6 @@
  */
 #define uninitialized_var(x) x = x
 
-#if GCC_VERSION >= 50100
+#if GCC_VERSION >= 50100 && !defined(__CHECKER__)
 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 #endif

Any idea?

Regards,
Miroslav

Re: sparse warnings in overflow.h

[Kees Cook]

On Thu, Jun 7, 2018 at 4:01 AM, Miroslav Benes <mbenes@suse.cz> wrote:
>
> Hi Kees,
>
> sparse (make C=1) gives me this warnings today...
>
> ./include/linux/overflow.h:254:13: error: undefined identifier '__builtin_mul_overflow'
> ./include/linux/overflow.h:254:13: error: incorrect type in conditional
> ./include/linux/overflow.h:254:13:    got void
> ./include/linux/overflow.h:256:13: error: undefined identifier '__builtin_add_overflow'
> ./include/linux/overflow.h:256:13: error: incorrect type in conditional
> ./include/linux/overflow.h:256:13:    got void
>
> This hunk obviously fixes it, but I'm really not sure if it is a proper
> fix.
>
> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> index f1a7492a5cc8..15e55b89e952 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -344,6 +344,6 @@
>   */
>  #define uninitialized_var(x) x = x
>
> -#if GCC_VERSION >= 50100
> +#if GCC_VERSION >= 50100 && !defined(__CHECKER__)
>  #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
>  #endif
>
> Any idea?

Hi! Yeah, that's probably the correct approach. If the checker doesn't
have it, the builtins need to be disabled. :)

Can you send this with a Signed-off-by line, etc, and I'll take it for
sending to Linus?

Thanks!

-Kees

-- 
Kees Cook
Pixel Security

Re: sparse warnings in overflow.h

[Rasmus Villemoes]

On 2018-06-07 20:35, Kees Cook wrote:
> On Thu, Jun 7, 2018 at 4:01 AM, Miroslav Benes <mbenes@suse.cz> wrote:
>>
>> Hi Kees,
>>
>> sparse (make C=1) gives me this warnings today...
>>
>> ./include/linux/overflow.h:254:13: error: undefined identifier '__builtin_mul_overflow'
>> ./include/linux/overflow.h:254:13: error: incorrect type in conditional
>> ./include/linux/overflow.h:254:13:    got void
>> ./include/linux/overflow.h:256:13: error: undefined identifier '__builtin_add_overflow'
>> ./include/linux/overflow.h:256:13: error: incorrect type in conditional
>> ./include/linux/overflow.h:256:13:    got void
>>
>> This hunk obviously fixes it, but I'm really not sure if it is a proper
>> fix.
>>
>> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
>> index f1a7492a5cc8..15e55b89e952 100644
>> --- a/include/linux/compiler-gcc.h
>> +++ b/include/linux/compiler-gcc.h
>> @@ -344,6 +344,6 @@
>>   */
>>  #define uninitialized_var(x) x = x
>>
>> -#if GCC_VERSION >= 50100
>> +#if GCC_VERSION >= 50100 && !defined(__CHECKER__)
>>  #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
>>  #endif
>>
>> Any idea?
> 
> Hi! Yeah, that's probably the correct approach. If the checker doesn't
> have it, the builtins need to be disabled. :)

IIRC, the problem is that sparse pretends to be the gcc sparse itself
was built with, which is obviously entirely unrelated to the C dialect
that that particular sparse version groks. Sigh. Ack to the fix above.

Rasmus

Re: sparse warnings in overflow.h

[Luc Van Oostenryck]

On Thu, Jun 07, 2018 at 09:25:09PM +0200, Rasmus Villemoes wrote:
> 
> IIRC, the problem is that sparse pretends to be the gcc sparse itself
> was built with, which is obviously entirely unrelated to the C dialect
> that that particular sparse version groks. Sigh. Ack to the fix above.

Yes, indeed, and it is sometimes a problem.
Ideal would be that sparse would pretend to be same GCC as the one used
to compile the code being checked *and* to have exactly the same features.

Pretending to be an older version of GCC would maybe solve the present
problem it's not really a general solution.

One good thing would be to not depend on GCC versions to enable some
features (but GCC offers few facilities helping here).


Best regards,
-- Luc Van Oostenryck

[PATCH] compiler-gcc.h: don't set COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW for sparse

[Miroslav Benes]

sparse errors out with

./include/linux/overflow.h:254:13: error: undefined identifier '__builtin_mul_overflow'
./include/linux/overflow.h:254:13: error: incorrect type in conditional
./include/linux/overflow.h:254:13:    got void
./include/linux/overflow.h:256:13: error: undefined identifier '__builtin_add_overflow'
./include/linux/overflow.h:256:13: error: incorrect type in conditional
./include/linux/overflow.h:256:13:    got void

Sparse has not acquired generic overflow builtins yet, so don't set
COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW for it.

Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 include/linux/compiler-gcc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index f1a7492a5cc8..15e55b89e952 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -344,6 +344,6 @@
  */
 #define uninitialized_var(x) x = x
 
-#if GCC_VERSION >= 50100
+#if GCC_VERSION >= 50100 && !defined(__CHECKER__)
 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 #endif
-- 
2.17.0