Re: [PATCH v2] arm64/cache: fix -Woverride-init compiler warnings

[Qian Cai]

> On Aug 7, 2019, at 6:56 AM, Will Deacon <will@xxxxxxxxxx> wrote:
> 
> On Tue, Aug 06, 2019 at 03:34:34PM -0400, Qian Cai wrote:
>> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
>> index 876055e37352..a0c495a3f4fd 100644
>> --- a/arch/arm64/kernel/cpuinfo.c
>> +++ b/arch/arm64/kernel/cpuinfo.c
>> @@ -34,10 +34,7 @@ DEFINE_PER_CPU(struct cpuinfo_arm64, cpu_data);
>> static struct cpuinfo_arm64 boot_cpu_data;
>> 
>> static char *icache_policy_str[] = {
>> -	[0 ... ICACHE_POLICY_PIPT]	= "RESERVED/UNKNOWN",
>> -	[ICACHE_POLICY_VIPT]		= "VIPT",
>> -	[ICACHE_POLICY_PIPT]		= "PIPT",
>> -	[ICACHE_POLICY_VPIPT]		= "VPIPT",
>> +	[0 ... ICACHE_POLICY_PIPT]	= "RESERVED/UNKNOWN"
>> };
>> 
>> unsigned long __icache_flags;
>> @@ -310,13 +307,16 @@ static void cpuinfo_detect_icache_policy(struct cpuinfo_arm64 *info)
>> 
>> 	switch (l1ip) {
>> 	case ICACHE_POLICY_PIPT:
>> +		icache_policy_str[ICACHE_POLICY_PIPT] = "PIPT";
>> 		break;
>> 	case ICACHE_POLICY_VPIPT:
>> +		icache_policy_str[ICACHE_POLICY_VPIPT] = "VPIPT";
>> 		set_bit(ICACHEF_VPIPT, &__icache_flags);
>> 		break;
>> 	default:
>> 		/* Fallthrough */
>> 	case ICACHE_POLICY_VIPT:
>> +		icache_policy_str[ICACHE_POLICY_VIPT] = "VIPT";
>> 		/* Assume aliasing */
>> 		set_bit(ICACHEF_ALIASING, &__icache_flags);
> 
> I still think this is worse than the code in mainline. I don't think
> -Woverride-init should warn when overriding a field from a GCC range
> designated initialiser, since it makes them considerably less useful
> imo.

Unfortunately, compiler people are moving into a different direction as
Clang would warn those kind of usage too.

It actually prove that those warnings are useful to find real issues. See,

Fae5e033d65a (âmfd: rk808: Fix RK818_IRQ_DISCHG_ILIM initializerâ)
32df34d875bb (â[media] rc: img-ir: jvc: Remove unused no-leader timingsâ)

Especially, to find redundant initializations in large structures. e.g.,

e6ea0b917875 (â[media] dvb_frontend: Don't declare values twice at a tableâ)