Re: [PATCH 01/15] arm: perf: cleanup cppcheck shifting error

[Peter Zijlstra]

On Sun, Jun 23, 2019 at 10:12:59PM +0700, Phong Tran wrote:
> fix "Shifting signed 32-bit value by 31 bits is undefined behaviour
> errors"
> 
> [arch/arm/kernel/perf_event_v7.c:1080]: (error) Shifting signed 32-bit
> value by 31 bits is undefined behaviour
> [arch/arm/kernel/perf_event_v7.c:1436]: (error) Shifting signed 32-bit
> value by 31 bits is undefined behaviour
> [arch/arm/kernel/perf_event_v7.c:1783]: (error) Shifting signed 32-bit
> value by 31 bits is undefined behaviour

I don't think that is true; the kernel uses -fno-strict-overflow (which
implies -fwrapv) and that takes away all the signed UB.