Re: toolchain/51094: repeatable file-system corruption: 7.99.2{7,8} i386/athlon gcc-5.3.0

[Jim Bernard <jbernard%mines.edu@localhost>]

The following reply was made to PR toolchain/51094; it has been noted by GNATS.

From: Jim Bernard <jbernard%mines.edu@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: toolchain-manager%NetBSD.org@localhost, gnats-admin%NetBSD.org@localhost,
        netbsd-bugs%NetBSD.org@localhost, jbernard%mines.edu@localhost
Subject: Re: toolchain/51094: repeatable file-system corruption: 7.99.2{7,8}
 i386/athlon gcc-5.3.0
Date: Thu, 28 Apr 2016 12:08:17 -0600

 On Tue, Apr 26, 2016 at 04:25:01PM +0000, Christos Zoulas wrote:
 >  -fno-tree-vrp
 
 Thanks for the suggestion.
 
 That makes the corruption problem go away, but I haven't managed to discover anything
 new about the source of the problem (apart from the fact that the combination of
 -ftree-vrp and -march-athlon-tbird leads to it).  Enabling all debugging options
 (DIAGNOSTIC, DEBUG, LOCKDEBUG) in a kernel with -march=athlon-tbird but not -fno-tree-vrp
 doesn't provide any new information beyond what I reported originally in the PR, AFAICT.
 The kernels I used as the basis for the original report all had options DIAGNOSTIC and
 DEBUG set, but not LOCKDEBUG.
 
 One thing that turned up in the last batch of tests, which isn't related to the
 file-system corruption, is that -fno-tree-vrp causes gcc to issue (fatal by default)
 warnings about the use of possibly uninitialized variables in four files:
 
   sys/external/bsd/drm2/drm/drm_scatter.c
     {sys/external/bsd/drm2/drm/drm_scatter.c:86:22: error:
       'sg' may be used uninitialized in this function [-Werror=maybe-uninitialized]}
   sys/dev/midictl.c
   sys/external/bsd/drm2/dist/drm/nouveau/core/subdev/clock/nouveau_subdev_clock_nv50.c
   sys/dev/usb/usbdi.c
 
 I don't know whether it's worthwhile to fix them.  If anybody would find them useful,
 I can regenerate the exact warning messages for the last three files.
 
 -- Jim