gcc11: jit build failure on macOS 11: Bootstrap comparison failure

[i0ntempest]

See buildbot log: ​https://build.macports.org/builders/ports-11_x86_64-builder/builds/41670/steps/install-port/logs/stdio

[mouse07410 (Mouse)]

Concur - same problem here. :-(

:info:build Comparing stages 2 and 3
:info:build warning: gcc/cc1obj-checksum.o differs
:info:build warning: gcc/cc1objplus-checksum.o differs
:info:build Bootstrap comparison failure!
:info:build gcc/jit/jit-recording.o differs
:info:build make[2]: *** [compare] Error 1
:info:build make[2]: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc11/gcc11/work/build'
:info:build make[1]: *** [stage3-bubble] Error 2
:info:build make[1]: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc11/gcc11/work/build'
:info:build make: *** [bootstrap-lean] Error 2
:info:build make: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc11/gcc11/work/build'
:info:build Command failed:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc11/gcc11/work/build" && /usr/bin/make -j20 -w bootstrap-lean 
:info:build Exit code: 2
:error:build Failed to build gcc11: command execution failed

Consistent on different machines (different CPUs, but all Intel and running macOS 11.5.1 with Xcode-12.5.1).

[i0ntempest]

Adding C expert Ken in to see if he got any ideas

[cjones051073 (Chris Jones)]

Just pushed

​https://github.com/macports/macports-ports/commit/22eeac18aba56f3c4d9edb7b62151dc90c720aab#diff-76e6422da629a86ac355b575a860262565d29a16740e1593f6d21f06fb394828

which for now disabled the jit build on Darwin 20+.

Lets leave this ticket open so can track a future fix to try and re-enable jit.

[wyuenho (Jimmy Yuen Ho Wong)]

Disabling jit broke emacs-devel and emacs-app-devel now. Are we able to revert gcc11 to the previous version?

[cjones051073 (Chris Jones)]

Not without bumping the epoch which I would like to avoid. Long term, we should alway keep up with the latest versions so that is also not a solution.

I would prefer to focus on fixing the issue with 11.2. I just didn't have time to do so right now so temporarily disabled jit. Please feel free to investigate yourself.

[kencu (Ken)]

the approach to these bootstrap comparison failures used by upstream is to disassemble the two non-matching objects and diff them. Then sort out what went wrong to make them different.

99% of them I have seen relate to different debugging format assumptions, but other hiccups can happen.

[cjones051073 (Chris Jones)]

I've added a comment to ​https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100340 to say the --without-build-config workaround no longer works properly. Lets see what they say.

[cjones051073 (Chris Jones)]

Should be fixed in the latest builds.