[Git][ghc/ghc][master] TH: fix Show/Eq/Ord instances for Bytes (#16457)
Marge Bot
gitlab at gitlab.haskell.org
Tue Apr 28 00:24:55 UTC 2020
Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC
Commits:
99823ed2 by Sylvain Henry at 2020-04-27T20:24:46-04:00
TH: fix Show/Eq/Ord instances for Bytes (#16457)
We shouldn't compare pointer values but the actual bytes.
- - - - -
5 changed files:
- libraries/template-haskell/Language/Haskell/TH/Syntax.hs
- libraries/template-haskell/changelog.md
- + testsuite/tests/th/TH_BytesShowEqOrd.hs
- + testsuite/tests/th/TH_BytesShowEqOrd.stdout
- testsuite/tests/th/all.T
Changes:
=====================================
libraries/template-haskell/Language/Haskell/TH/Syntax.hs
=====================================
@@ -45,12 +45,15 @@ import GHC.Generics ( Generic )
import GHC.Types ( Int(..), Word(..), Char(..), Double(..), Float(..),
TYPE, RuntimeRep(..) )
import GHC.Prim ( Int#, Word#, Char#, Double#, Float#, Addr# )
+import GHC.Ptr ( Ptr, plusPtr )
import GHC.Lexeme ( startsVarSym, startsVarId )
import GHC.ForeignSrcLang.Type
import Language.Haskell.TH.LanguageExtensions
import Numeric.Natural
import Prelude
import Foreign.ForeignPtr
+import Foreign.C.String
+import Foreign.C.Types
-----------------------------------------------------
--
@@ -1868,7 +1871,45 @@ data Bytes = Bytes
-- , bytesInitialized :: Bool -- ^ False: only use `bytesSize` to allocate
-- -- an uninitialized region
}
- deriving (Eq,Ord,Data,Generic,Show)
+ deriving (Data,Generic)
+
+-- We can't derive Show instance for Bytes because we don't want to show the
+-- pointer value but the actual bytes (similarly to what ByteString does). See
+-- #16457.
+instance Show Bytes where
+ show b = unsafePerformIO $ withForeignPtr (bytesPtr b) $ \ptr ->
+ peekCStringLen ( ptr `plusPtr` fromIntegral (bytesOffset b)
+ , fromIntegral (bytesSize b)
+ )
+
+-- We can't derive Eq and Ord instances for Bytes because we don't want to
+-- compare pointer values but the actual bytes (similarly to what ByteString
+-- does). See #16457
+instance Eq Bytes where
+ (==) = eqBytes
+
+instance Ord Bytes where
+ compare = compareBytes
+
+eqBytes :: Bytes -> Bytes -> Bool
+eqBytes a@(Bytes fp off len) b@(Bytes fp' off' len')
+ | len /= len' = False -- short cut on length
+ | fp == fp' && off == off' = True -- short cut for the same bytes
+ | otherwise = compareBytes a b == EQ
+
+compareBytes :: Bytes -> Bytes -> Ordering
+compareBytes (Bytes _ _ 0) (Bytes _ _ 0) = EQ -- short cut for empty Bytes
+compareBytes (Bytes fp1 off1 len1) (Bytes fp2 off2 len2) =
+ unsafePerformIO $
+ withForeignPtr fp1 $ \p1 ->
+ withForeignPtr fp2 $ \p2 -> do
+ i <- memcmp (p1 `plusPtr` fromIntegral off1)
+ (p2 `plusPtr` fromIntegral off2)
+ (fromIntegral (min len1 len2))
+ return $! (i `compare` 0) <> (len1 `compare` len2)
+
+foreign import ccall unsafe "memcmp"
+ memcmp :: Ptr a -> Ptr b -> CSize -> IO CInt
-- | Pattern in Haskell given in @{}@
=====================================
libraries/template-haskell/changelog.md
=====================================
@@ -10,6 +10,12 @@
and `unTypeQ` are also generalised in terms of `Quote` rather than specific
to `Q`.
+ * Fix Eq/Ord instances for `Bytes`: we were comparing pointers while we should
+ compare the actual bytes (#16457).
+
+ * Fix Show instance for `Bytes`: we were showing the pointer value while we
+ want to show the contents (#16457).
+
## 2.16.0.0 *TBA*
* Add support for tuple sections. (#15843) The type signatures of `TupE` and
=====================================
testsuite/tests/th/TH_BytesShowEqOrd.hs
=====================================
@@ -0,0 +1,40 @@
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE BangPatterns #-}
+
+module Main where
+
+import Language.Haskell.TH.Lib
+import GHC.Ptr
+import Foreign.ForeignPtr
+
+main :: IO ()
+main = do
+
+ let
+ !x = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz"#
+ !y = "ABCDEabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz"#
+
+ p1 <- newForeignPtr_ (Ptr x)
+ p2 <- newForeignPtr_ (Ptr y)
+
+ let
+ b1 = mkBytes p1 0 5
+ b2 = mkBytes p1 10 5
+ b3 = mkBytes p1 26 5
+ b4 = mkBytes p2 5 5
+ b5 = mkBytes p2 10 5
+
+ let myCmp a b = putStrLn $ "compare " ++ show a ++ " to " ++ show b ++ " => " ++ show (compare a b)
+
+ putStr "same pointer, same offset, same bytes: "
+ myCmp b1 b1
+ putStr "same pointer, different offset, same bytes: "
+ myCmp b1 b3
+ putStr "same pointer, different offset, different bytes: "
+ myCmp b1 b2
+ putStr "same pointer, different offset, different bytes: "
+ myCmp b2 b1
+ putStr "different pointer, different offset, same bytes: "
+ myCmp b1 b4
+ putStr "different pointer, different offset, different bytes: "
+ myCmp b1 b5
=====================================
testsuite/tests/th/TH_BytesShowEqOrd.stdout
=====================================
@@ -0,0 +1,6 @@
+same pointer, same offset, same bytes: compare abcde to abcde => EQ
+same pointer, different offset, same bytes: compare abcde to abcde => EQ
+same pointer, different offset, different bytes: compare abcde to klmno => LT
+same pointer, different offset, different bytes: compare klmno to abcde => GT
+different pointer, different offset, same bytes: compare abcde to abcde => EQ
+different pointer, different offset, different bytes: compare abcde to fghij => LT
=====================================
testsuite/tests/th/all.T
=====================================
@@ -504,3 +504,4 @@ test('T17688a', normal, compile, [''])
test('T17688b', normal, compile, [''])
test('TH_PprStar', normal, compile, ['-v0 -dsuppress-uniques'])
test('TH_StringLift', normal, compile, [''])
+test('TH_BytesShowEqOrd', normal, compile_and_run, [''])
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/99823ed24b22447b14202ca57f75550773c44dbe
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/99823ed24b22447b14202ca57f75550773c44dbe
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