Re: [PATCH] mdadm: fix gcc8 maybe-uninitialized/format-overflow warning

[Adrian Bunk <bunk@stusta.de>]

On Wed, Mar 20, 2019 at 08:59:39AM -0400, Khem Raj wrote:
> On Wed, Mar 20, 2019 at 1:21 AM Adrian Bunk <bunk@stusta.de> wrote:
> >
> > On Tue, Mar 19, 2019 at 11:51:47PM -0400, Khem Raj wrote:
> > > On Fri, Mar 15, 2019 at 6:45 AM Adrian Bunk <bunk@stusta.de> wrote:
> > > >
> > > > On Tue, Mar 12, 2019 at 05:41:58PM +0800, changqing.li@windriver.com wrote:
> > > > > From: Changqing Li <changqing.li@windriver.com>
> > > > >
> > > > > while compiled with -Werror=maybe-uninitialized/-Werror=format-overflow=,
> > > > > it failed
> > > > >
> > > > > [snip]
> > > > > | Incremental.c: In function 'Incremental_container':
> > > > > | Incremental.c:1593:3: error: 'mdfd' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> > > > > | close(mdfd);
> > > > > | ^~~~~~~~~~~
> > > > >
> > > > > [snip]
> > > > > super-intel.c: In function 'apply_takeover_update':
> > > > > | super-intel.c:9615:15: error: '%d' directive writing between 1 and 11 bytes into a region of size 7 [-Werror=format-overflow=]
> > > > > | " MISSING_%d", du->index);
> > > > > | ^~
> > > > >...
> > > >
> > > > I am seeing these warnings only with -Og, are you also seeing them with
> > > > -Og (DEBUG_OPTIMIZATION) only?
> > > >
> > > > If this is true, I would consider
> > > > https://sources.debian.org/src/mdadm/4.1-2/debian/patches/debian-no-Werror.diff/
> > > > a better workaround.
> > > >
> > > This seems a broader brush, I really dont like to relegate Werror if
> > > we dont have to, because it will force us
> > > to fix the code.
> >
> > How are we getting such fixes properly reviewed?
> >
> > What actually happens is that the easiest change that silences a warning
> > gets applied.
> >
> > And for such bogus -Og only warnings there was no problem in the code,
> 
> so then probably a better fix is to add -Wno-error to DEBUG_FLAGS
> which will limit it to -Og case, and revert the original fix.

For mdadm this might work, for puzzles it would not.

Order matters, and upstream can insert your flags before or after
the -Werror. So unfortunately this would not cover all recipes.

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed