Hi all, On Thu, 11 Jan 2024 17:37:12 +0100 "Arnd Bergmann" <arnd@xxxxxxxx> wrote: > > On Thu, Jan 11, 2024, at 13:55, Arnd Bergmann wrote: > > On Thu, Jan 11, 2024, at 12:16, Dan Carpenter wrote: > >> On Thu, Jan 11, 2024 at 04:23:09PM +0530, Naresh Kamboju wrote: > >>> Following build failures noticed on i386 and x86 with clang builds on the > >>> Linux next-20240111 tag. > >>> > >>> Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx> > >>> > >>> Build error: > >>> ---------- > >>> mm/vmalloc.c:4691:25: error: variable 'addr' is uninitialized when > >>> used here [-Werror,-Wuninitialized] > >>> 4691 | va = __find_vmap_area(addr, &vn->busy.root); > >>> | ^~~~ > >>> mm/vmalloc.c:4684:20: note: initialize the variable 'addr' to silence > >>> this warning > >>> 4684 | unsigned long addr; > >>> | ^ > >>> | = 0 > >>> 1 error generated. > >> > >> We turned off uninitialized variable warnings for GCC a long time ago... > >> :/ I don't know if we'll be able to re-enable it in a -Werror world > >> although Clang seems to be managing alright so perhaps there is hope. > > > > The problem with gcc's warning is that it is non-deterministic and > > in recent versions actually got more false-positives even without > > -Os or -fsanitize=. Clang does not catch all that gcc does because > > it doesn't track state across inline functions, but at least its > > output is always the same regardless of optimization and other > > options. > > > > At least this particular one is an obvious bug and easily gets > > caught by lkft and lkp even if gcc's -Wuninitilized doesn't > > flag it. > > As it turns out, gcc did find this one in the default -Wuninitialized > regardless of -Wmaybe-uninitialized: > > mm/vmalloc.c: In function 'vmalloc_dump_obj': > mm/vmalloc.c:4691:22: error: 'addr' is used uninitialized [-Werror=uninitialized] > 4691 | va = __find_vmap_area(addr, &vn->busy.root); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > mm/vmalloc.c:4684:23: note: 'addr' was declared here > 4684 | unsigned long addr; > | ^~~~ > > and I see that Uladzislau Rezki already sent a fix, which > is the same that I tried out in my randconfig tree: > https://lore.kernel.org/lkml/ZaARXdbigD1hWuOS@xxxxxxxxx/ I have applied that to linux-next today. -- Cheers, Stephen Rothwell
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