Re: [PULL v2 05/13] target/rx: CPU definitions

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 3/20/20 5:21 PM, Peter Maydell wrote:
> On Fri, 20 Mar 2020 at 16:19, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>>
>> On 3/20/20 9:04 AM, Philippe Mathieu-Daudé wrote:
>>> Not related to this patch, but this line generates a warning with Clang:
>>>
>>>    CC      rx-softmmu/target/rx/cpu.o
>>> target/rx/cpu.c:158:33: warning: The result of the left shift is undefined
>>> because the left operand is negative
>>>      address = physical = addr & TARGET_PAGE_MASK;
>>>                                  ^~~~~~~~~~~~~~~~
>>> include/exec/cpu-all.h:234:45: note: expanded from macro 'TARGET_PAGE_MASK'
>>> #define TARGET_PAGE_MASK   ((target_long)-1 << TARGET_PAGE_BITS)
>>>                              ~~~~~~~~~~~~~~~ ^
>>> 1 warning generated.
>>
>> >From configure:
>>
>>> # We use -fwrapv to tell the compiler that we require a C dialect where
>>> # left shift of signed integers is well defined and has the expected
>>> # 2s-complement style results. (Both clang and gcc agree that it
>>> # provides these semantics.)
>>
>> Clang is *supposed* to be not generating those warnings.
> 
> I do have clang in my build tests, so at least some versions of
> clang do indeed correctly handle -fwrapv. What version are
> you using, Philippe ?

-fwrapv is here indeed.

I use 
--extra-cflags=-fsanitize=address,alignment,array-bounds,bool,builtin,enum,float-cast-overflow,float-divide-by-zero,function,integer-divide-by-zero,nonnull-attribute,null,pointer-overflow,return,returns-nonnull-attribute,shift-base,shift-exponent,signed-integer-overflow,unreachable,vla-bound,vptr

Apparently -fwrapv is ignored. Probably one of shift-base/shift-exponent 
sanitizer plugins.

> 
> thanks
> -- PMM
>