Messages in this thread | | | Subject | Re: [PATCH] arm64/cache: fix -Woverride-init compiler warnings | From | Qian Cai <> | Date | Mon, 5 Aug 2019 23:50:03 -0400 |
| |
> On Aug 5, 2019, at 10:01 AM, Will Deacon <will@kernel.org> wrote: > > On Mon, Aug 05, 2019 at 07:47:37AM -0400, Qian Cai wrote: >> >> >>> On Aug 5, 2019, at 5:52 AM, Will Deacon <will@kernel.org> wrote: >>> >>> On Fri, Aug 02, 2019 at 11:32:24AM -0400, Qian Cai wrote: >>>> The commit 155433cb365e ("arm64: cache: Remove support for ASID-tagged >>>> VIVT I-caches") introduced some compiation warnings from GCC, >>>> >>>> arch/arm64/kernel/cpuinfo.c:38:26: warning: initialized field >>>> overwritten [-Woverride-init] >>>> [ICACHE_POLICY_VIPT] = "VIPT", >>>> ^~~~~~ >>>> arch/arm64/kernel/cpuinfo.c:38:26: note: (near initialization for >>>> 'icache_policy_str[2]') >>>> arch/arm64/kernel/cpuinfo.c:39:26: warning: initialized field >>>> overwritten [-Woverride-init] >>>> [ICACHE_POLICY_PIPT] = "PIPT", >>>> ^~~~~~ >>>> arch/arm64/kernel/cpuinfo.c:39:26: note: (near initialization for >>>> 'icache_policy_str[3]') >>>> arch/arm64/kernel/cpuinfo.c:40:27: warning: initialized field >>>> overwritten [-Woverride-init] >>>> [ICACHE_POLICY_VPIPT] = "VPIPT", >>>> ^~~~~~~ >>>> arch/arm64/kernel/cpuinfo.c:40:27: note: (near initialization for >>>> 'icache_policy_str[0]') >>>> >>>> because it initializes icache_policy_str[0 ... 3] twice. >>>> >>>> Fixes: 155433cb365e ("arm64: cache: Remove support for ASID-tagged VIVT I-caches") >>>> Signed-off-by: Qian Cai <cai@lca.pw> >>>> --- >>>> arch/arm64/kernel/cpuinfo.c | 4 ++-- >>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c >>>> index 876055e37352..193b38da8d96 100644 >>>> --- a/arch/arm64/kernel/cpuinfo.c >>>> +++ b/arch/arm64/kernel/cpuinfo.c >>>> @@ -34,10 +34,10 @@ >>>> static struct cpuinfo_arm64 boot_cpu_data; >>>> >>>> static char *icache_policy_str[] = { >>>> - [0 ... ICACHE_POLICY_PIPT] = "RESERVED/UNKNOWN", >>>> + [ICACHE_POLICY_VPIPT] = "VPIPT", >>>> + [ICACHE_POLICY_VPIPT + 1] = "RESERVED/UNKNOWN", >>>> [ICACHE_POLICY_VIPT] = "VIPT", >>>> [ICACHE_POLICY_PIPT] = "PIPT", >>>> - [ICACHE_POLICY_VPIPT] = "VPIPT", >>> >>> I really don't like this patch. Using "[0 ... MAXIDX] = <default>" is a >>> useful idiom and I think the code is more error-prone the way you have >>> restructured it. >>> >>> Why are you passing -Woverride-init to the compiler anyway? There's only >>> one Makefile that references that option, and it's specific to a pinctrl >>> driver. >> >> Those extra warnings can be enabled by “make W=1”. “-Woverride-init “ seems to be useful >> to catch potential developer mistakes with unintented double-initializations. It is normal to >> start to fix the most of false-positives first before globally enabling the flag by default just like >> “-Wimplicit-fallthrough” mentioned in, >> >> https://lwn.net/Articles/794944/ > > I think this case is completely different to the implicit fallthrough stuff. > The solution there was simply to add a comment without restructuring the > surrounding code. What your patch does here is actively make the code harder > to understand. > > Initialising a static array with a non-zero pattern is a useful idiom and I > don't think we should throw that away just to appease a silly compiler > warning that appears only with non-default build options. Have a look at > the way we use PERF_MAP_ALL_UNSUPPORTED in the Arm PMU code, for example.
Well, both GCC and Clang would generate warnings for those. Clang even enable this by default,
https://releases.llvm.org/8.0.0/tools/clang/docs/DiagnosticsReference.html#winitializer-overrides
Assume compiler people are sane, I probably not call those are “silly”.
| |