Date: Fri, 5 Feb 2021 07:30:51 +0800 From: Erich Dollansky <freebsd.ed.lists@sumeritec.com> To: Frank Leonhardt <frank2@fjl.co.uk> Cc: freebsd-questions@freebsd.org Subject: Re: Warnings when compiling kernel Message-ID: <20210204233051.560f4f64.freebsd.ed.lists@sumeritec.com> In-Reply-To: <4a8b2522-2046-6212-9a40-ce1d6c4a0473@fjl.co.uk> References: <alpine.BSF.2.23.453.2101312121500.2098@fbsd.local> <4a8b2522-2046-6212-9a40-ce1d6c4a0473@fjl.co.uk>
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Hi,
On Wed, 3 Feb 2021 22:34:28 +0000
Frank Leonhardt <frank2@fjl.co.uk> wrote:
> 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.
>
words like 'may have' are the reason for countless software errors.
Erich
> Regards, Frank.
>
>
>
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