[PATCH 1/2] powerpc/64s: Work around spurious warning on old gccs with -fsanitize-coverage

[Andrew Donnellan]

On 7/2/19 5:37 pm, Segher Boessenkool wrote:
> On Thu, Feb 07, 2019 at 04:33:23PM +1100, Andrew Donnellan wrote:
>> Some older gccs (<GCC 7), when invoked with -fsanitize-coverage=trace-pc,
>> cause a spurious uninitialised variable warning in dt_cpu_ftrs.c:
>>
>>    arch/powerpc/kernel/dt_cpu_ftrs.c: In function ‘cpufeatures_process_feature’:
>>    arch/powerpc/kernel/dt_cpu_ftrs.c:686:7: warning: ‘m’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>>      if (m->cpu_ftr_bit_mask)
> 
> It seems to me the warning is correct?  If enable_unknown is false and no
> cpu_feature is found, it will in
> 
> 	if (m->cpu_ftr_bit_mask)
> 		cur_cpu_spec->cpu_features |= m->cpu_ftr_bit_mask;
> 
> enable random features (whatever was last in the table), or indeed access
> via NULL if the table is length 0?  So maybe this should be
> 
> 	if (known && m->cpu_ftr_bit_mask)
> 		cur_cpu_spec->cpu_features |= m->cpu_ftr_bit_mask;
> 
> instead?  (The code would be much clearer if all the known vs. !known
> codepath was fully separated here).

The table is never length 0, it's a statically defined array.

> 
> 
> Segher
> 

-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan at au1.ibm.com  IBM Australia Limited