diff options
| -rw-r--r-- | compiler/basicTypes/Unique.hs | 16 | ||||
| -rw-r--r-- | compiler/iface/MkIface.hs | 9 | ||||
| -rw-r--r-- | testsuite/tests/determinism/determ002/A.hs | 10 | ||||
| -rw-r--r-- | testsuite/tests/determinism/determ002/Makefile | 13 | ||||
| -rw-r--r-- | testsuite/tests/determinism/determ002/all.T | 4 | ||||
| -rw-r--r-- | testsuite/tests/determinism/determ002/determ002.stderr | 0 | ||||
| -rw-r--r-- | testsuite/tests/determinism/determ002/determ002.stdout | 2 |
7 files changed, 53 insertions, 1 deletions
diff --git a/compiler/basicTypes/Unique.hs b/compiler/basicTypes/Unique.hs index 5ce9c64a0c..12629ff91a 100644 --- a/compiler/basicTypes/Unique.hs +++ b/compiler/basicTypes/Unique.hs @@ -174,6 +174,22 @@ use `deriving' because we want {\em precise} control of ordering (equality on @Uniques@ is v common). -} +-- Note [Unique Determinism] +-- ~~~~~~~~~~~~~~~~~~~~~~~~~ +-- The order of allocated @Uniques@ is not stable across rebuilds. +-- The main reason for that is that typechecking interface files pulls +-- @Uniques@ from @UniqSupply@ and the interface file for the module being +-- currently compiled can, but doesn't have to exist. +-- +-- It gets more complicated if you take into account that the interface +-- files are loaded lazily and that building multiple files at once has to +-- work for any subset of interface files present. When you add parallelism +-- this makes @Uniques@ hopelessly random. +-- +-- As such, to get deterministic builds, the order of the allocated +-- @Uniques@ should not affect the final result. +-- see also wiki/DeterministicBuilds + eqUnique, ltUnique, leUnique :: Unique -> Unique -> Bool eqUnique (MkUnique u1) (MkUnique u2) = u1 == u2 ltUnique (MkUnique u1) (MkUnique u2) = u1 < u2 diff --git a/compiler/iface/MkIface.hs b/compiler/iface/MkIface.hs index 66a885bb6d..d4b764b613 100644 --- a/compiler/iface/MkIface.hs +++ b/compiler/iface/MkIface.hs @@ -1700,7 +1700,14 @@ tyConToIfaceDecl env tycon ifaceOverloaded flds = case fsEnvElts flds of fl:_ -> flIsOverloaded fl [] -> False - ifaceFields flds = map flLabel $ fsEnvElts flds + ifaceFields flds = sort $ map flLabel $ fsEnvElts flds + -- We need to sort the labels because they come out + -- of FastStringEnv in arbitrary order, because + -- FastStringEnv is keyed on Uniques. + -- Sorting FastString is ok here, because Uniques + -- are only used for equality checks in the Ord + -- instance for FastString. + -- See Note [Unique Determinism] in Unique. toIfaceBang :: TidyEnv -> HsImplBang -> IfaceBang toIfaceBang _ HsLazy = IfNoBang diff --git a/testsuite/tests/determinism/determ002/A.hs b/testsuite/tests/determinism/determ002/A.hs new file mode 100644 index 0000000000..9a88f2c319 --- /dev/null +++ b/testsuite/tests/determinism/determ002/A.hs @@ -0,0 +1,10 @@ +module A where + +-- This is a repro for the issue where to fingerprint a record, field labels +-- were pulled from FastStringEnv in the order of Uniques which are known +-- to have arbitrary order - see Note [Unique Determinism] in Unique. + +data B = C + { e :: () + , d :: () + } diff --git a/testsuite/tests/determinism/determ002/Makefile b/testsuite/tests/determinism/determ002/Makefile new file mode 100644 index 0000000000..d94a1c22ec --- /dev/null +++ b/testsuite/tests/determinism/determ002/Makefile @@ -0,0 +1,13 @@ +TOP=../../.. +include $(TOP)/mk/boilerplate.mk +include $(TOP)/mk/test.mk + +TEST_HC_OPTS_NO_RECOMP = $(filter-out -fforce-recomp,$(TEST_HC_OPTS)) + +determ002: + $(RM) A.hi A.o + '$(TEST_HC)' $(TEST_HC_OPTS_NO_RECOMP) A.hs + $(CP) A.hi A.old.hi + $(RM) A.o + '$(TEST_HC)' $(TEST_HC_OPTS_NO_RECOMP) A.hs + diff A.hi A.old.hi diff --git a/testsuite/tests/determinism/determ002/all.T b/testsuite/tests/determinism/determ002/all.T new file mode 100644 index 0000000000..9bfd05db00 --- /dev/null +++ b/testsuite/tests/determinism/determ002/all.T @@ -0,0 +1,4 @@ +test('determ002', + extra_clean(['A.o', 'A.hi', 'A.old.hi']), + run_command, + ['$MAKE -s --no-print-directory determ002']) diff --git a/testsuite/tests/determinism/determ002/determ002.stderr b/testsuite/tests/determinism/determ002/determ002.stderr new file mode 100644 index 0000000000..e69de29bb2 --- /dev/null +++ b/testsuite/tests/determinism/determ002/determ002.stderr diff --git a/testsuite/tests/determinism/determ002/determ002.stdout b/testsuite/tests/determinism/determ002/determ002.stdout new file mode 100644 index 0000000000..60c2bc368d --- /dev/null +++ b/testsuite/tests/determinism/determ002/determ002.stdout @@ -0,0 +1,2 @@ +[1 of 1] Compiling A ( A.hs, A.o ) +[1 of 1] Compiling A ( A.hs, A.o ) |