linux-kernel - RE: Compile problems w/gcc 9.4.0 in linux-next

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Message-ID:
 <SN6PR02MB4157AF07EC9A5566473CC135D4A52@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Sun, 23 Mar 2025 17:52:17 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Nick Terrell <terrelln@...a.com>, Ingo Molnar <mingo@...nel.org>
CC: Ard Biesheuvel <ardb@...nel.org>, "dsterba@...e.com" <dsterba@...e.com>,
	"brgerst@...il.com" <brgerst@...il.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: Compile problems w/gcc 9.4.0 in linux-next

From: Nick Terrell <terrelln@...a.com> Sent: Saturday, March 22, 2025 9:58 PM
> 
> > On Mar 22, 2025, at 12:36 AM, Ingo Molnar <mingo@...nel.org> wrote:
> > 
> > * Michael Kelley <mhklinux@...look.com> wrote:
> >
> >> From: Ingo Molnar <mingo@...nel.org> Sent: Friday, March 21, 2025 12:38 AM
> >>>
> >>> * Michael Kelley <mhklinux@...look.com> wrote:
> >>>
> >>>>> What are your thoughts as maintainers of lib/zstd?
> >>>>
> >>>> FYI, the same segfault occurs with gcc 10.5. The problem is fixed
> >>>> in gcc 11.4.
> >>>
> >>> So the patch below would work this around on GCC9 and GCC10?
> >>
> >> I've confirmed that the patch gives a clean compile with gcc 9.4.
> >>
> >> Note that I confirmed yesterday that the gcc problem is fixed with
> >> 11.4. I don't know about earlier gcc 11 minor versions. Lemme see
> >> if I can get the original gcc 11 release and try that to confirm that
> >> your patch has the right version cutoff.

After a bunch of manual wrangling, I finally got gcc-11.1.0-1 installed
alongside gcc-9.4.0 in a clean Ubuntu 20.04 VM. As expected,
building linux-next-20250321 with gcc-9.4.0 fails.  And building with
gcc-11.1.0-1 compiles with no problems, and the resulting kernel
runs correctly.

gcc-11.1.0-1 is the earliest 11.x version I can find. It's from the
Debian repo archives. Interestingly, gcc-11.1.0-1 also requires
binutils 2.35.2-2 (it fails with 2.34), so I had to manually install those
packages as well. But 11.4.0 works fine with binutils 2.34, so maybe
they downgraded the requirements at some point in the minor
update stream.

Michael

> >
> > Thank you for the testing!
> 
> I've submitted that patch here:
> 
> https://lore.kernel.org/lkml/20250323050749.165863-1-nickrterrell@gmail.com/
> 
> I've merged it into my linux-next branch as well.
> 
> Best,
> Nick Terrell
> 
> >>> +++ b/lib/zstd/common/portability_macros.h
> >>> @@ -55,7 +55,7 @@
> >>> #ifndef DYNAMIC_BMI2
> >>>   #if ((defined(__clang__) && __has_attribute(__target__)) \
> >>>       || (defined(__GNUC__) \
> >>> -          && (__GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)))) \
> >>> +          && (__GNUC__ >= 11))) \
> >>>       && (defined(__x86_64__) || defined(_M_X64)) \
> >>>       && !defined(__BMI2__)
> >>>   #  define DYNAMIC_BMI2 1
> >
> > Worst case, if it isn't, I suppose we'll get followup bug reports.
> >
> > Thanks,
> >
> > Ingo
>