Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: f1cb08be by Hannes Siebenhandl at 2026-10-05T22:05:03-04:00 Prepend in-memory unit database for backpack The packageDbFlags are stored in reverse order. Thus, prepending will ensure that the in-memory unit database is the last item on the unit database stack. Further, the in-memory unit database needs to be able to shadow units from earlier unit databases in the unit database stack. Moreover, a `-clear-package-db` would remove the in-memory database if it weren't the last item on the stack. Closes #27835 - - - - - 5 changed files: - changelog.d/unit-index - compiler/GHC/Driver/Backpack.hs - + testsuite/tests/backpack/should_compile/T27835.bkp - + testsuite/tests/backpack/should_compile/T27835.stderr - testsuite/tests/backpack/should_compile/all.T Changes: ===================================== changelog.d/unit-index ===================================== @@ -1,7 +1,7 @@ section: compiler synopsis: Use global ``UnitIndex`` to deduplicate ``UnitInfo``s over multiple home units -issues: #27500 #26423 #27748 #27834 -mrs: !16115 !16598 !16743 +issues: #27500 #26423 #27748 #27834 #27835 +mrs: !16115 !16598 !16743 !16748 description: { The ``UnitState`` used to be duplicated for all ``HomeUnitEnv``, not sharing any of the ``UnitInfo``s. ===================================== compiler/GHC/Driver/Backpack.hs ===================================== @@ -441,9 +441,11 @@ addInMemoryDatabase dflags u = do } let uic = hscUIC hsc_env liftIO $ cacheExternalUnitDatabase uic newdb - -- added at the end because ordering matters + -- Ordering matters here! We prepend the new unit database, because 'packageDBFlags' + -- works like a stack, where what's on top takes precedence over what's below (same as right-to-left when given at the CLI). + -- The new db needs highest precedence to overwrite any other in-memory units that potentially occur in the dbs below it. pure dflags - { packageDBFlags = packageDBFlags dflags ++ [PackageDB (PkgDbPath (unitDatabasePath newdb))] + { packageDBFlags = PackageDB (PkgDbPath (unitDatabasePath newdb)) : packageDBFlags dflags } -- | Register a new virtual unit database containing a single unit ===================================== testsuite/tests/backpack/should_compile/T27835.bkp ===================================== @@ -0,0 +1,11 @@ +unit p where + module P where + p :: Int + p = 42 + +unit q where + dependency p + module Q where + import P + q :: Int + q = p + 1 ===================================== testsuite/tests/backpack/should_compile/T27835.stderr ===================================== @@ -0,0 +1,7 @@ +[1 of 2] Processing p + Instantiating p + [1 of 1] Compiling P ( p/P.hs, T27835.out/p/P.o ) +[2 of 2] Processing q + Instantiating q + [1 of 1] Including p + [1 of 1] Compiling Q ( q/Q.hs, T27835.out/q/Q.o ) ===================================== testsuite/tests/backpack/should_compile/all.T ===================================== @@ -61,3 +61,4 @@ test('T13250', normal, backpack_compile, ['']) test('T13323', normal, backpack_compile, ['']) test('T20396', normal, backpack_compile, ['']) test('T23424', [ignore_stdout, ignore_stderr], backpack_compile, ['-ddump-rn-trace -ddump-if-trace -ddump-tc-trace']) +test('T27835', normal, backpack_compile, ['-clear-package-db -global-package-db']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f1cb08bee1ad6ae5b23b162a7e56280a... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f1cb08bee1ad6ae5b23b162a7e56280a... You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help