> On 24. May 2018, at 08:36, Matthew Macy <mm...@freebsd.org> wrote: > > On Wed, May 23, 2018 at 11:35 PM, Michael Tuexen > <michael.tue...@macmic.franken.de> wrote: >>> On 24. May 2018, at 06:51, Matthew Macy <mm...@freebsd.org> wrote: >>> >>> Warnings find bugs PERIOD. Although most are not useful, I've found >> Some warnings indicate bugs, some warnings are just wrong. If you >> have a "may be used uninitialized" warning being a false positive, you >> may silences the warning by just set it to zero in the declaration and >> you silence it. Other compilers might then correctly report an >> assignment without affect... > > I have yet to see a double assignment be flagged as assignment without > effect. If it _does_ occur then we have to disable the warning on the > compiler that we have less faith in. Have seen it in the past in a difference project... But you miss my point:
Not all warnings indicate bugs PERIOD. Some warning are just wrong... Best regards Michael > -M > > >> >> Best regards >> Michael >>> quite a number of real issues from compiling with gcc8. >>> >>> If you want to _actually_ be helpful fix these: >>> https://people.freebsd.org/~mmacy/gcc8logs/GENERIC-NODEBUG.log >>> >>> https://people.freebsd.org/~mmacy/gcc8logs/GENERIC.log >>> >>> On Wed, May 23, 2018 at 9:42 PM, Gleb Smirnoff <gleb...@freebsd.org> wrote: >>>> Let me repeat again. The warning is a false positive, and thus assignment >>>> isn't useful. I'm not worried about a single instruction, more about >>>> polluting the code. >>>> >>>> If the warning was escalated to build error, and we did carry about >>>> building with gcc8, in this case the assignment should be added with >>>> a comment /* pacify gcc */. >>>> >>>> On Wed, May 23, 2018 at 03:59:33PM -0700, Matthew Macy wrote: >>>> M> On Wed, May 23, 2018 at 3:57 PM, Gleb Smirnoff <gleb...@freebsd.org> >>>> wrote: >>>> M> > The initialization isn't useful. >>>> M> >>>> M> It silences a gcc warning. So yes it is. It's this exchange which is >>>> not useful. >>>> M> >>>> M> -M >>>> M> >>>> M> >>>> M> > On Wed, May 23, 2018 at 03:52:42PM -0700, Matthew Macy wrote: >>>> M> > M> Talk to the gcc devs. The warning is useful even if there are >>>> false positives. >>>> M> > M> >>>> M> > M> On Wed, May 23, 2018 at 3:27 PM, Gleb Smirnoff >>>> <gleb...@freebsd.org> wrote: >>>> M> > M> > Hi, >>>> M> > M> > >>>> M> > M> > On Sat, May 19, 2018 at 05:10:52AM +0000, Matt Macy wrote: >>>> M> > M> > M> Author: mmacy >>>> M> > M> > M> Date: Sat May 19 05:10:51 2018 >>>> M> > M> > M> New Revision: 333860 >>>> M> > M> > M> URL: https://svnweb.freebsd.org/changeset/base/333860 >>>> M> > M> > M> >>>> M> > M> > M> Log: >>>> M> > M> > M> sendfile: annotate unused value and ensure that npages is >>>> actually initialized >>>> M> > M> > M> >>>> M> > M> > M> Modified: >>>> M> > M> > M> head/sys/kern/kern_sendfile.c >>>> M> > M> > M> >>>> M> > M> > M> Modified: head/sys/kern/kern_sendfile.c >>>> M> > M> > M> >>>> ============================================================================== >>>> M> > M> > M> --- head/sys/kern/kern_sendfile.c Sat May 19 05:09:10 2018 >>>> (r333859) >>>> M> > M> > M> +++ head/sys/kern/kern_sendfile.c Sat May 19 05:10:51 2018 >>>> (r333860) >>>> M> > M> > M> @@ -341,7 +341,7 @@ sendfile_swapin(vm_object_t obj, struct >>>> sf_io *sfio, o >>>> M> > M> > M> } >>>> M> > M> > M> >>>> M> > M> > M> for (int i = 0; i < npages;) { >>>> M> > M> > M> - int j, a, count, rv; >>>> M> > M> > M> + int j, a, count, rv __unused; >>>> M> > M> > M> >>>> M> > M> > M> /* Skip valid pages. */ >>>> M> > M> > M> if (vm_page_is_valid(pa[i], vmoff(i, off) & >>>> PAGE_MASK, >>>> M> > M> > M> @@ -688,6 +688,7 @@ retry_space: >>>> M> > M> > M> if (space == 0) { >>>> M> > M> > M> sfio = NULL; >>>> M> > M> > M> nios = 0; >>>> M> > M> > M> + npages = 0; >>>> M> > M> > M> goto prepend_header; >>>> M> > M> > M> } >>>> M> > M> > M> hdr_uio = NULL; >>>> M> > M> > >>>> M> > M> > This initialization is redundant and a compiler warning if >>>> exists is wrong. >>>> M> > M> > >>>> M> > M> > If we jump down to prepend_header with nios == 0, we won't ever >>>> use npages. >>>> M> > M> > >>>> M> > M> > -- >>>> M> > M> > Gleb Smirnoff >>>> M> > >>>> M> > -- >>>> M> > Gleb Smirnoff >>>> >>>> -- >>>> Gleb Smirnoff >>> >> _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"