Hello,

the new RTL optimization introduced in [1] breaks the gcc-14 build on m68k.

As discovered by the Gentoo m68k maintainers, building gcc-14 with the option
-fno-fold-mem-offsets to disable this new optimization fixes this problem.

The option does not seem to be needed on gcc-15 which builds fine in experimental [2].

I have used the following patch against the gcc-14 package to pass the option
during build which works for me:
--- debian/rules2.orig	 2025-02-19 16:04:38.000000000 +0100
+++ debian/rules2	 2025-06-06 11:55:20.606692824 +0200
@@ -227,6 +227,17 @@
   endif
 endif

+ifeq ($(DEB_TARGET_ARCH),m68k)
+  CFLAGS               += -fno-fold-mem-offsets
+  CXXFLAGS             += -fno-fold-mem-offsets
+  CFLAGS_FOR_BUILD     += -fno-fold-mem-offsets
+  CXXFLAGS_FOR_BUILD   += -fno-fold-mem-offsets
+  CFLAGS_FOR_TARGET    += -fno-fold-mem-offsets
+  CXXFLAGS_FOR_TARGET  += -fno-fold-mem-offsets
+  BOOT_CFLAGS          += -fno-fold-mem-offsets
+  STAGE1_CFLAGS        += -fno-fold-mem-offsets
+endif
+
 ifneq (,$(findstring -fno-omit-frame-pointer,$(shell DEB_HOST_ARCH=$(DEB_TARGET_ARCH) dpkg-buildflags --get CFLAGS)))
   CFLAGS_FRAME_POINTER = -fno-omit-frame-pointer
 else

The gcc maintainer will certainly know better whether all of these are
needed to fix the build and consequently avoid other packages from being
miscompiled or failing to build.

Thanks,
Adrian

Hi,

I was not able to tune gcc-14 properly using CFLAGS to apply this workaround
when using gcc-13 as the bootstrap compiler but the attached patch worked for
me which of course can't be used in the actual package.

It should be possible to add -fno-fold-mem-offsets to DRIVER_SELF_SPECS on
m68k. However, I currently don't understand how the syntax works. I'll
ask the Gentoo people who have done this.

Adrian

We believe that the bug you reported is fixed in the latest version of
gcc-14, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1107416@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Matthias Klose <doko@debian.org> (supplier of updated gcc-14 package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Mon, 09 Jun 2025 10:59:15 +0200
Source: gcc-14
Architecture: source
Version: 14.3.0-2
Distribution: experimental
Urgency: medium
Maintainer: Debian GCC Maintainers <debian-gcc@lists.debian.org>
Changed-By: Matthias Klose <doko@debian.org>
Closes: 1107416
Changes:
 gcc-14 (14.3.0-2) experimental; urgency=medium
 .
   * Update to git 20250609 from the gcc-14 branch.
     - Fix PR target/119834 (S390), PR middle-end/118819,
       PR rtl-optimization/117239, PR rtl-optimization/117239,
       PR tree-optimization/117358, PR target/86772 (microblaze),
       PR c++/120123, PR c++/120161, PR fortran/85750, PR fortran/98454,
       PR target/120441 (AVR).
   * Don't default to -fno-fold-mem-offsets on m68k (Adrian Glaubitz).
     Closes: #1107416.
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We believe that the bug you reported is fixed in the latest version of
gcc-15, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1107416@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Matthias Klose <doko@debian.org> (supplier of updated gcc-15 package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Mon, 09 Jun 2025 13:27:55 +0200
Source: gcc-15
Architecture: source
Version: 15.1.0-6
Distribution: experimental
Urgency: medium
Maintainer: Debian GCC Maintainers <debian-gcc@lists.debian.org>
Changed-By: Matthias Klose <doko@debian.org>
Closes: 1107416
Changes:
 gcc-15 (15.1.0-6) experimental; urgency=medium
 .
   * Update to git 20250609 from the gcc-15 branch.
     - Fix PR tree-optimization/120357, PR tree-optimization/120341,
       PR rtl-optimization/120182, PR tree-optimization/120003,
       PR tree-optimization/119960, PR tree-optimization/116352,
       PR target/86772 (microblaze), PR c/120180, PR c++/120123, PR c/120180,
       PR c++/120413, PR c++/120363, PR c++/120414, PR fortran/99838,
       PR fortran/102599, PR fortran/114022, PR fortran/101735,
       PR fortran/101735, PR fortran/120193, PR fortran/120049,
       PR fortran/120355, PR target/120442 (AVR), PR target/120441 (AVR),
       PR libfortran/119856, PR middle-end/118694, PR middle-end/118694,
       PR libstdc++/120432, PR libstdc++/120465, PR libstdc++/120367.
   * Don't default to -ffold-mem-offsets on m68k (Adrian Glaubitz).
     Closes: #1107416.
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Hi,

This didn't work, unfortunately [1]. However, I used Gemini to come up with the
attached patch which fixes the glibc build problem for me. Can you include it
instead?

Thanks,
Adrian

Hi,

For clarification, this patch should be applied on m68k only, see [1].

Adrian

Hi,

I'm going to test this proposed patch now [1].

Adrian