Date: Wed, 3 Feb 2021 22:37:29 +0000 From: freebsd-doc@fjl.co.uk To: freebsd-questions@freebsd.org Subject: Re: Warnings when compiling kernel Message-ID: <4f819960-db08-190f-e0d3-5d4c55cd104e@fjl.co.uk> In-Reply-To: <alpine.BSF.2.23.453.2101312121500.2098@fbsd.local> References: <alpine.BSF.2.23.453.2101312121500.2098@fbsd.local>
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On 31/01/2021 21:22, Roderick wrote:
>
> Are they normal?
>
> """""""""""""""""""""""""""""""""""""
> cc -c -O2 -pipe -fno-strict-aliasing -std=c99 -Wall
> -Wredundant-decls -Wnested-externs -Wstrict-prototypes
> -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual -Wundef
> -Wno-pointer-sign -fformat-extensions -Wmissing-include-dirs
> -fdiagnostics-show-option -Wno-error-tautological-compare
> -Wno-error-empty-body -Wno-error-parentheses-equality
> -Wno-error-unused-function -nostdinc -I. -I/usr/src/sys
> -I/usr/src/sys/contrib/altq -I/usr/src/sys/contrib/libfdt -D_KERNEL
> -DHAVE_KERNEL_OPTION_HEADERS -include opt_global.h -mno-aes -mno-avx
> -mno-mmx -mno-sse -msoft-float -ffreestanding -fstack-protector
> -Werror /usr/src/sys/kern/kern_cpuset.c
> /usr/src/sys/kern/kern_cpuset.c:637:16: warning: comparison of unsigned
> expression < 0 is always false [-Wtautological-compare]
> for (i = 0; i < (_NCPUWORDS - 1); i++) {
> ~ ^ ~~~~~~~~~~~~~~~~
> 1 warning generated.
>
Compiler warnings are normal, but I'd rather they weren't there myself.
I wish I knew which file generated the error (it's not from any of the
kernels I have loaded), and which CPU was the target, as I can't be sure
what happens next. However, _NCPUWORDS can quite easily be 1, which
means the for() loop will never be executed on some CPUs. One would hope
the optimiser would remove it completely if this was the case, and this
may have been the intention.
Regards, Frank.
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