Date: Wed, 23 May 2018 22:13:25 -0700 From: Matthew Macy <mmacy@freebsd.org> To: Gleb Smirnoff <glebius@freebsd.org> Cc: src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r333860 - head/sys/kern Message-ID: <CAPrugNri9xu6DeNR5pXWv6UjFEDuKuZD5LGbyvQAFKM-5F87mg@mail.gmail.com> In-Reply-To: <20180524050717.GY71675@FreeBSD.org> References: <201805190510.w4J5AqfS054367@repo.freebsd.org> <20180523222743.GU71675@FreeBSD.org> <CAPrugNpKxEVx%2Bg0D6qUwq=yw_W-QeuntupwAjteK1yALkJktag@mail.gmail.com> <20180523225729.GV71675@FreeBSD.org> <CAPrugNpsiYQ1MKkgGbkwPEeTcsTCdD_u5GAvYpMJKHzeSbCL=w@mail.gmail.com> <20180524044252.GW71675@FreeBSD.org> <CAPrugNoVPCbB0qTY=Z1dwCZ%2BbCbVbA1d5b0-tw5qaPxWRK0q8g@mail.gmail.com> <20180524050717.GY71675@FreeBSD.org>
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On Wed, May 23, 2018 at 10:07 PM, Gleb Smirnoff <glebius@freebsd.org> wrote: > Can you please explain the bug supposed to be fixed by r333860 QUESTION MARK Did I say it fixed a bug? Or are you saying we should just turn off compiler warnings because Gleb Smirnoff knows better? -M > On Wed, May 23, 2018 at 09:51:34PM -0700, Matthew Macy wrote: > M> Warnings find bugs PERIOD. Although most are not useful, I've found > M> quite a number of real issues from compiling with gcc8. > M> > M> If you want to _actually_ be helpful fix these: > M> https://people.freebsd.org/~mmacy/gcc8logs/GENERIC-NODEBUG.log > M> > M> https://people.freebsd.org/~mmacy/gcc8logs/GENERIC.log > M> > M> On Wed, May 23, 2018 at 9:42 PM, Gleb Smirnoff <glebius@freebsd.org> wrote: > M> > Let me repeat again. The warning is a false positive, and thus assignment > M> > isn't useful. I'm not worried about a single instruction, more about > M> > polluting the code. > M> > > M> > If the warning was escalated to build error, and we did carry about > M> > building with gcc8, in this case the assignment should be added with > M> > a comment /* pacify gcc */. > M> > > M> > On Wed, May 23, 2018 at 03:59:33PM -0700, Matthew Macy wrote: > M> > M> On Wed, May 23, 2018 at 3:57 PM, Gleb Smirnoff <glebius@freebsd.org> wrote: > M> > M> > The initialization isn't useful. > M> > M> > 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> > M> > M> > M> > M> > M> > On Wed, May 23, 2018 at 03:52:42PM -0700, Matthew Macy wrote: > M> > M> > M> Talk to the gcc devs. The warning is useful even if there are false positives. > M> > M> > M> > M> > M> > M> On Wed, May 23, 2018 at 3:27 PM, Gleb Smirnoff <glebius@freebsd.org> wrote: > M> > M> > M> > Hi, > M> > M> > M> > > M> > M> > M> > On Sat, May 19, 2018 at 05:10:52AM +0000, Matt Macy wrote: > M> > M> > M> > M> Author: mmacy > M> > M> > M> > M> Date: Sat May 19 05:10:51 2018 > M> > M> > M> > M> New Revision: 333860 > M> > M> > M> > M> URL: https://svnweb.freebsd.org/changeset/base/333860 > M> > M> > M> > M> > M> > M> > M> > M> Log: > M> > M> > M> > M> sendfile: annotate unused value and ensure that npages is actually initialized > M> > M> > M> > M> > M> > M> > M> > M> Modified: > M> > M> > M> > M> head/sys/kern/kern_sendfile.c > M> > M> > M> > M> > M> > M> > M> > M> Modified: head/sys/kern/kern_sendfile.c > M> > M> > M> > M> ============================================================================== > M> > M> > M> > M> --- head/sys/kern/kern_sendfile.c Sat May 19 05:09:10 2018 (r333859) > M> > M> > M> > M> +++ head/sys/kern/kern_sendfile.c Sat May 19 05:10:51 2018 (r333860) > M> > 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> > M> > M> > M> for (int i = 0; i < npages;) { > M> > M> > M> > M> - int j, a, count, rv; > M> > M> > M> > M> + int j, a, count, rv __unused; > M> > M> > M> > M> > M> > M> > M> > M> /* Skip valid pages. */ > M> > M> > M> > M> if (vm_page_is_valid(pa[i], vmoff(i, off) & PAGE_MASK, > M> > M> > M> > M> @@ -688,6 +688,7 @@ retry_space: > M> > M> > M> > M> if (space == 0) { > M> > M> > M> > M> sfio = NULL; > M> > M> > M> > M> nios = 0; > M> > M> > M> > M> + npages = 0; > M> > M> > M> > M> goto prepend_header; > M> > M> > M> > M> } > M> > M> > M> > M> hdr_uio = NULL; > M> > M> > M> > > M> > M> > M> > This initialization is redundant and a compiler warning if exists is wrong. > M> > M> > 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> > -- > M> > M> > M> > Gleb Smirnoff > M> > M> > > M> > M> > -- > M> > M> > Gleb Smirnoff > M> > > M> > -- > M> > Gleb Smirnoff > > -- > Gleb Smirnoff
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