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

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

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