1.28.0-1 FTBFS in Jammy - libldc-jit.so not built

[Christian Ehrhardt ]

This is FTFBS for 12 days now
https://launchpadlibrarian.net/569860671/buildlog_ubuntu-jammy-amd64.ldc_1%3A1.28.0-1_BUILDING.txt.gz

The same in Debian worked fine
https://buildd.debian.org/status/fetch.php?pkg=ldc&arch=amd64&ver=1%3A1.28.0-1%2Bb1&stamp=1636718694&raw=1

Our fail is:
   dh_install
dh_install: warning: Cannot find (any matches for) "usr/lib/libldc-jit.so.*" (tried in ., debian/tmp)

dh_install: warning: libphobos2-ldc-shared98 missing files: usr/lib/libldc-jit.so.*
dh_install: warning: Cannot find (any matches for) "usr/lib/libldc-jit.so" (tried in ., debian/tmp)

dh_install: warning: libphobos2-ldc-shared-dev missing files: usr/lib/libldc-jit.so
dh_install: warning: Cannot find (any matches for) "usr/lib/libldc-jit-rt.a" (tried in ., debian/tmp)

dh_install: warning: libphobos2-ldc-shared-dev missing files: usr/lib/libldc-jit-rt.a

And the reason those do not exists seems to be in our config step already.
We have llvm 13 (biggest difference to Debian which has 11 still).

...
-- -- Building LDC with dynamic compilation support (LDC_DYNAMIC_COMPILE): OFF
...

While Debian has ON at the same config step.

This is locally reproducible in sbuild (the good Debian and the bad ubuntu build) and there via:

mkdir buildtest; cd buildtest; cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=None -DCMAKE_INSTALL_SYSCONFDIR=/etc -DCMAKE_INSTALL_LOCALSTATEDIR=/var -DCMAKE_EXPORT_NO_PACKAGE_REGISTRY=ON -DCMAKE_FIND_USE_PACKAGE_REGISTRY=OFF -DCMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY=ON -DCMAKE_INSTALL_RUNSTATEDIR=/run "-GUnix Makefiles" -DCMAKE_VERBOSE_MAKEFILE=ON -DCMAKE_INSTALL_LIBDIR=lib/x86_64-linux-gnu -DD_COMPILER=/usr/bin/gdmd -DBUILD_SHARED_LIBS=ON ..

[Christian Ehrhardt  (paelzer)]

Well, the LDC code is rather straight forward on this:

CMakeLists.txt:452
set(LDC_DYNAMIC_COMPILE "AUTO" CACHE STRING "Support dynamic compilation (ON|OFF). Enabled by default; not supported for LLVM >= 12.")

It turns out this is due to the internal ORCv1 API (dropped with LLVM 12) vs ORCv2 (added with LLVM 7).

In LDC this is known-disabled since
https://github.com/ldc-developers/ldc/commit/d8bc064cfbc766347d563cb139a72d238312bd38#diff-1e7de1ae2d059d21e1dd75d5812d5a34b0222cef273b7c3a2af62eb747f9d20a

This is known upstream
https://github.com/ldc-developers/ldc/issues/3747
https://github.com/ldc-developers/ldc/pull/3184

Not a Problem for Debian yet until LLVM>=12 is the default.

For now we should be able to get this working by forcing llvm-11-dev

[Christian Ehrhardt  (paelzer)]

Test config works fine, local build still ongoing.
If it succeeds I'll upload this to jammy.

[Christian Ehrhardt  (paelzer)]

The Upstream Author confirmed that this was an experimental feature and the right way forward probably is to disable it:
=> https://github.com/ldc-developers/ldc/issues/3747#issuecomment-975690206

For now I'll build it with llvm-11 (= as before)
=> uploaded

But to resolve it mid term I filed a bug with the backgrounds and the suggestion to disable it with Debian.
=> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1000431

[Launchpad Janitor (janitor)]

This bug was fixed in the package ldc - 1:1.28.0-1ubuntu1

---------------
ldc (1:1.28.0-1ubuntu1) jammy; urgency=medium

  * d/control: force llvm-11 as ldc dynamic compile (jit) isn't
    compatible with >=12 (LP: #1951845)

 -- Christian Ehrhardt <email address hidden> Mon, 22 Nov 2021 16:33:44 +0100