On Thu, Dec 18, 2025 at 9:21 AM Philippe Mathieu-Daudé
<[email protected]> wrote:
>
> Hi Gustavo,
>
> On 17/12/25 22:20, Gustavo Romero wrote:
> > Add a sentinel to the ARMASIdx enum so it can be used when the total
> > number of address spaces is required.
> >
> > Signed-off-by: Gustavo Romero <[email protected]>
> > ---
> > target/arm/cpu.h | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> > index 39f2b2e54d..00f5af0fcd 100644
> > --- a/target/arm/cpu.h
> > +++ b/target/arm/cpu.h
> > @@ -2336,6 +2336,7 @@ typedef enum ARMASIdx {
> > ARMASIdx_S = 1,
> > ARMASIdx_TagNS = 2,
> > ARMASIdx_TagS = 3,
> > + ARMASIdx_MAX
>
My two cents:
Here, "ARMASIdx_MAX" should be equal to the last variant, 3. So to get
the total count, it would be ARMASIdx_MAX + 1.
And it should be called "ARMASIdx_COUNT". Max is the last variant.
> The problem with including this in the enum is this confuses static
> analyzers:
>
> warning: enumeration value 'ARMASIdx_MAX' not handled in switch [-Wswitch]
>
If we add a "MAX" instead of "COUNT" variant, then the value of the
MAX variant would be handled in switch cases. The following
definition does not emit a warning with -Wswitch:
typedef enum ARMASIdx {
ARMASIdx_NS = 0,
ARMASIdx_S = 1,
ARMASIdx_TagNS = 2,
ARMASIdx_TagS = 3,
ARMASIdx_MAX = ARMASIdx_TagS,
#define ARMASIdx_COUNT (ARMASIdx_MAX + 1)
} ARMASIdx;
int main() {
ARMASIdx t = ARMASIdx_S;
switch (t) {
case ARMASIdx_NS:
break;
case ARMASIdx_S:
break;
case ARMASIdx_TagNS:
break;
case ARMASIdx_TagS:
break;
}
printf("Last = %d Count = %d\n", ARMASIdx_MAX, ARMASIdx_COUNT);
}
Outputs:
"Last = 3 Count = 4"
> To avoid that we /define/ it manually instead:
>
> #define ARMASIdx_MAX 4
>
> > } ARMASIdx;
>
> Usually the definition is within the enum declaration, and we name
> it ${enum}_COUNT:
>
> typedef enum ARMASIdx {
> ARMASIdx_NS = 0,
> ARMASIdx_S = 1,
> ARMASIdx_TagNS = 2,
> ARMASIdx_TagS = 3,
> #define ARMASIdx_COUNT 4
> } ARMASIdx;
>
> Unfortunately this didn't work well with QAPI, so we could never enable
> -Wswitch globally:
> https://lore.kernel.org/qemu-devel/[email protected]/
>
> Today I'm not sure what is the best style anymore, so just take
> my comments are historical 2 cents.
>
> Regards,
>
> Phil.
>
