structs 0.1.7 → 0.1.8
raw patch · 3 files changed
+86/−3 lines, 3 filesdep ~template-haskelldep ~th-abstraction
Dependency ranges changed: template-haskell, th-abstraction
Files
- CHANGELOG.markdown +6/−0
- src/Data/Struct/Internal.hs +78/−2
- structs.cabal +2/−1
CHANGELOG.markdown view
@@ -1,3 +1,9 @@+## 0.1.8 [2023.02.22]+* Avoid some dodgy uses of `unsafeCoerce#` from `Any` (a lifted type) to+ `MutableByteArray# s` (an unlifted type) in the internals of the library.+ While these uses of `unsafeCoerce#` have not been observed to cause any+ improper behavior at runtime, the previous situation was rather delicate.+ ## 0.1.7 [2023.01.22] * Avoid a particularly dodgy use of `unsafeCoerce#` in the implementation of `isNil` when building with GHC 9.4 or later. This is necessary to make the
src/Data/Struct/Internal.hs view
@@ -1,6 +1,7 @@ {-# LANGUAGE CPP #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE Unsafe #-}+{-# LANGUAGE DataKinds #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE MagicHash #-} {-# LANGUAGE RankNTypes #-}@@ -11,6 +12,11 @@ {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE DefaultSignatures #-}++#if __GLASGOW_HASKELL__ < 806+{-# LANGUAGE TypeInType #-}+#endif+ {-# OPTIONS_HADDOCK not-home #-} ----------------------------------------------------------------------------- -- |@@ -31,6 +37,10 @@ import Data.Coerce import GHC.Exts +#if MIN_VERSION_base(4,15,0)+import Unsafe.Coerce (unsafeCoerceUnlifted)+#endif+ -- $setup -- >>> import Control.Monad.Primitive @@ -159,26 +169,92 @@ -- * Faking SmallMutableArrayArray#s -------------------------------------------------------------------------------- +{-+The types of writeSmallArray#, readSmallArray#, and casSmallArray# became+levity polymorphic in @base-4.17.0.0@, which allows us to coerce from a+@SmallMutableArray# s Any@ to a @SmallMutableArray# s (SmallMutableArray# s+Any)@ or a @SmallMutableArray# s MutableByteArray#@. These types are all of+kind UnliftedType, so we can accomplish this coercion using+unsafeCoerceUnlifted instead of its dodgier alternative, unsafeCoerce#.++On older versions of base, SmallMutableArray# is of kind @Type -> Type ->+UnliftedType@, so we must resort to sketchier uses of unsafeCoerce#. For+instance, the implementation of readMutableByteArraySmallArray# must coerce from+this type:++ SmallMutableArray# s Any -> Int# -> State# s -> (# State# s, Any #)++To this type:++ SmallMutableArray# s Any -> Int# -> State# s -> (# State# s, MutableByteArray# s #)++This implies coercing (Any :: Type) to (MutableByteArray# s :: UnliftedType).+This is on shaky ground, as the coercion changes a lifted type to an unlifted+type! Unfortunately, we can't really do better given SmallMutableArray#'s+restrictive kind.++Note that both the pre- and post-@base-4.17.0.0@ versions of the code use the+same number of unsafe coercions. The difference lies in whether you are+coercing from @Any@ to @MutableByteArray# s@ (a kind-heterogeneous coercion)+versus coercing from @SmallMutableArray# s Any@ to @SmallMutableArray# s+(MutableByteArray# s)@ (a kind-homogeneous coercion). You'll still need /some/+sort of unsafe coercion given the fact that the @structs@ library uniformly+represents everything as @SmallMutableArray# s Any@, but at the very least, the+latter types of coercions avoid casting directly from lifted to unlifted types.++See https://gitlab.haskell.org/ghc/ghc/-/issues/22813 for the GHC issue that+led to the current design of this code.+-}+ writeSmallMutableArraySmallArray# :: SmallMutableArray# s Any -> Int# -> SmallMutableArray# s Any -> State# s -> State# s+#if MIN_VERSION_base(4,17,0)+writeSmallMutableArraySmallArray# m i a s = writeSmallArray# (unsafeCoerceUnlifted m) i a s+#else writeSmallMutableArraySmallArray# m i a s = unsafeCoerce# writeSmallArray# m i a s+#endif {-# INLINE writeSmallMutableArraySmallArray# #-} readSmallMutableArraySmallArray# :: SmallMutableArray# s Any -> Int# -> State# s -> (# State# s, SmallMutableArray# s Any #)+#if MIN_VERSION_base(4,17,0)+readSmallMutableArraySmallArray# m i s = readSmallArray# (unsafeCoerceUnlifted m) i s+#else readSmallMutableArraySmallArray# m i s = unsafeCoerce# readSmallArray# m i s+#endif {-# INLINE readSmallMutableArraySmallArray# #-} writeMutableByteArraySmallArray# :: SmallMutableArray# s Any -> Int# -> MutableByteArray# s -> State# s -> State# s+#if MIN_VERSION_base(4,17,0)+writeMutableByteArraySmallArray# m i a s = writeSmallArray# (unsafeCoerceUnlifted m) i a s+#else writeMutableByteArraySmallArray# m i a s = unsafeCoerce# writeSmallArray# m i a s+#endif {-# INLINE writeMutableByteArraySmallArray# #-} readMutableByteArraySmallArray# :: SmallMutableArray# s Any -> Int# -> State# s -> (# State# s, MutableByteArray# s #)+#if MIN_VERSION_base(4,17,0)+readMutableByteArraySmallArray# m i s = readSmallArray# (unsafeCoerceUnlifted m) i s+#else readMutableByteArraySmallArray# m i s = unsafeCoerce# readSmallArray# m i s+#endif {-# INLINE readMutableByteArraySmallArray# #-} casSmallMutableArraySmallArray# :: SmallMutableArray# s Any -> Int# -> SmallMutableArray# s Any -> SmallMutableArray# s Any -> State# s -> (# State# s, Int#, SmallMutableArray# s Any #)+#if MIN_VERSION_base(4,17,0)+casSmallMutableArraySmallArray# m i o n s = casSmallArray# (unsafeCoerceUnlifted m) i o n s+#else casSmallMutableArraySmallArray# m i o n s = unsafeCoerce# casSmallArray# m i o n s+#endif {-# INLINE casSmallMutableArraySmallArray# #-} +#if !(MIN_VERSION_base(4,15,0))+unsafeCoerceUnlifted :: forall (a :: TYPE UnliftedRep) (b :: TYPE UnliftedRep). a -> b+unsafeCoerceUnlifted = unsafeCoerce#+#endif++#if !(MIN_VERSION_base(4,10,0))+type UnliftedRep = PtrRepUnlifted+#endif+ -------------------------------------------------------------------------------- -- * Field Accessors --------------------------------------------------------------------------------@@ -235,8 +311,8 @@ -- | Store the reference to the Haskell data type in a normal field field :: Int {- ^ slot -} -> Field s a field (I# i) = Field- (\m s -> unsafeCoerce# readSmallArray# m i s)- (\m a s -> unsafeCoerce# writeSmallArray# m i a s)+ (\m s -> readSmallArray# (unsafeCoerceUnlifted m) i s)+ (\m a s -> writeSmallArray# (unsafeCoerceUnlifted m) i a s) {-# INLINE field #-} -- | Store the reference in the nth slot in the nth argument, treated as a MutableByteArray
structs.cabal view
@@ -1,6 +1,6 @@ name: structs category: Data-version: 0.1.7+version: 0.1.8 license: BSD3 cabal-version: 1.22 license-file: LICENSE@@ -53,6 +53,7 @@ Data.Struct.Order ghc-options: -Wall -fwarn-monomorphism-restriction -fwarn-identities -fwarn-incomplete-record-updates -fwarn-incomplete-uni-patterns -fno-warn-wrong-do-bind+ -Wno-unticked-promoted-constructors hs-source-dirs: src default-language: Haskell2010