Re: [PATCH 4/4] target/ppc: fix warning with clang-15

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

On 2/14/23 08:14, Philippe Mathieu-Daudé wrote:
> On 13/2/23 17:13, Pierrick Bouvier wrote:
>> When compiling for windows-arm64 using clang-15, it reports a sometimes
>> uninitialized variable. This seems to be a false positive, as a default
>> case guards switch expressions, preventing to return an uninitialized
>> value, but clang seems unhappy with assert definition.
>>
>> Setting the rnd variable to zero does not hurt anyway.
>>
>> ../target/ppc/dfp_helper.c:141:13: error: variable 'rnd' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]                                                                              assert(0); /* cannot get here */                                                                                                                                                                                    ^~~~~~~~~
>> ../include/qemu/osdep.h:229:20: note: expanded from macro 'assert'                                                                                                                                        #define assert(x)  g_assert(x)                                                                                                                                                                                                         ^~~~~~~~~~~
>> /clangarm64/bin/../include/glib-2.0/glib/gtestutils.h:235:49: note: expanded from macro 'g_assert'                                                                                                                               if G_LIKELY (expr) ; else \
>>                                                   ^~~~~~~~~~~~~~~
>> /clangarm64/bin/../include/glib-2.0/glib/gmacros.h:1186:25: note: expanded from macro 'G_LIKELY'
>>                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> ../target/ppc/dfp_helper.c:144:42: note: uninitialized use occurs here
>>       decContextSetRounding(&dfp->context, rnd);
>>
>> Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
>> ---
>>    target/ppc/dfp_helper.c | 4 ++--
>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/target/ppc/dfp_helper.c b/target/ppc/dfp_helper.c
>> index cc024316d5..0b4b280683 100644
>> --- a/target/ppc/dfp_helper.c
>> +++ b/target/ppc/dfp_helper.c
>> @@ -69,7 +69,7 @@ struct PPC_DFP {
>>    
>>    static void dfp_prepare_rounding_mode(decContext *context, uint64_t fpscr)
>>    {
>> -    enum rounding rnd;
>> +    enum rounding rnd = 0;
>>    
>>        switch ((fpscr & FP_DRN) >> FPSCR_DRN0) {
>>        case 0:
>> @@ -106,7 +106,7 @@ static void dfp_prepare_rounding_mode(decContext *context, uint64_t fpscr)
>>    static void dfp_set_round_mode_from_immediate(uint8_t r, uint8_t rmc,
>>                                                      struct PPC_DFP *dfp)
>>    {
>> -    enum rounding rnd;
>> +    enum rounding rnd = 0;
> 
> Could DEC_ROUND_DEFAULT be clearer?
> 

I missed that macro definition, and that seems like a good default 
value. I'll change to this.