linux-kernel - Re: [BUG] allmodconfig build error in next-20240108

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Date: Tue, 9 Jan 2024 19:46:27 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Stephen Rothwell <sfr@...b.auug.org.au>
Cc: Lucas De Marchi <lucas.demarchi@...el.com>,
	linux-kernel@...r.kernel.org, intel-xe@...ts.freedesktop.org
Subject: Re: [BUG] allmodconfig build error in next-20240108

On Wed, Jan 10, 2024 at 09:58:22AM +1100, Stephen Rothwell wrote:
> Hi all,
> 
> On Tue, 9 Jan 2024 14:45:56 -0800 "Paul E. McKenney" <paulmck@...nel.org> wrote:
> >
> > On Wed, Jan 10, 2024 at 08:11:55AM +1100, Stephen Rothwell wrote:
> > > 
> > > On Tue, 9 Jan 2024 10:58:40 -0600 Lucas De Marchi <lucas.demarchi@...el.com> wrote:  
> > > >
> > > > On Mon, Jan 08, 2024 at 03:15:23PM -0800, Paul E. McKenney wrote:  
> > > > I could reproduce it with allmodconfig and gcc 11.4.1 from rockylinux,
> > > > but not with gcc 9.3 or 12.3. Also it's not reproduced with gcc 11.4.1
> > > > when using defconfig + CONFIG_DRM_XE  (even if  -Wstringop-overflow is
> > > > still added).
> > > > 
> > > > I don't see a bug in the code, even if it inverts the head/tail
> > > > convention.
> > > > 
> > > > Searching around showed this which may be relevant: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101854
> > > > At least I can reproduce the same issue as in the snippet provided
> > > > (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101854#c7) with the buggy
> > > > compiler.
> > > > 
> > > > So, maybe the best thing to do for now is to disable -Wstringop-overflow
> > > > for gcc < 12?
> > > > 
> > > > 
> > > > ------8<-----
> > > > diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
> > > > index 6952da8979ea..0433a3c6cbfd 100644
> > > > --- a/drivers/gpu/drm/xe/Makefile
> > > > +++ b/drivers/gpu/drm/xe/Makefile
> > > > @@ -17,7 +17,7 @@ subdir-ccflags-y += $(call cc-option, -Wunused-const-variable)
> > > >   subdir-ccflags-y += $(call cc-option, -Wpacked-not-aligned)
> > > >   subdir-ccflags-y += $(call cc-option, -Wformat-overflow)
> > > >   subdir-ccflags-y += $(call cc-option, -Wformat-truncation)
> > > > -subdir-ccflags-y += $(call cc-option, -Wstringop-overflow)
> > > > +subdir-ccflags-$(call gcc-min-version, 120000) += $(call cc-option, -Wstringop-overflow)
> > > >   subdir-ccflags-y += $(call cc-option, -Wstringop-truncation)
> > > >   # The following turn off the warnings enabled by -Wextra
> > > >   ifeq ($(findstring 2, $(KBUILD_EXTRA_WARN)),)
> > > > ------8<-----  
> > 
> > This I did, thank you!
> 
> Maybe that line "subdir-ccflags-y += $(call cc-option, -Wstringop-overflow)"
> should just be removed as the setting of that option has been moved to the
> normal C flags in the top level Makefile (out of Makefile.extrawarn).

If you meant like this, no joy.  :-(

							Thanx, Paul

------------------------------------------------------------------------

diff --git a/Makefile b/Makefile
index 0705e7426ab7..446bd2da9fa3 100644
--- a/Makefile
+++ b/Makefile
@@ -988,7 +988,6 @@ KBUILD_CFLAGS += $(call cc-option, -fstrict-flex-arrays=3)
 
 #Currently, disable -Wstringop-overflow for GCC 11, globally.
 KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-option, -Wno-stringop-overflow)
-KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
 
 # disable invalid "can't wrap" optimizations for signed / pointers
 KBUILD_CFLAGS	+= -fno-strict-overflow