base: Use keepAlive# in Foreign.Marshal.Alloc

(cherry picked from commit 5813cdffc6ae5fbd23af9d6f8526373e46f5623c)

1 files changed, 4 insertions, 25 deletions

diff --git a/libraries/base/Foreign/Marshal/Alloc.hs b/libraries/base/Foreign/Marshal/Alloc.hs
index c32f0b62d7..573ed3dbc4 100644
--- a/libraries/base/Foreign/Marshal/Alloc.hs
+++ b/libraries/base/Foreign/Marshal/Alloc.hs
@@ -116,19 +116,6 @@ alloca :: forall a b . Storable a => (Ptr a -> IO b) -> IO b
 alloca  =
   allocaBytesAligned (sizeOf (undefined :: a)) (alignment (undefined :: a))
 
--- Note [NOINLINE for touch#]
--- ~~~~~~~~~~~~~~~~~~~~~~~~~~
--- Both allocaBytes and allocaBytesAligned use the touch#, which is notoriously
--- fragile in the presence of simplification (see #14346). In particular, the
--- simplifier may drop the continuation containing the touch# if it can prove
--- that the action passed to allocaBytes will not return. The hack introduced to
--- fix this for 8.2.2 is to mark allocaBytes as NOINLINE, ensuring that the
--- simplifier can't see the divergence.
---
--- These can be removed once #14375 is fixed, which suggests that we instead do
--- away with touch# in favor of a primitive that will capture the scoping left
--- implicit in the case of touch#.
-
 -- |@'allocaBytes' n f@ executes the computation @f@, passing as argument
 -- a pointer to a temporarily allocated block of memory of @n@ bytes.
 -- The block of memory is sufficiently aligned for any of the basic
@@ -143,12 +130,8 @@ allocaBytes (I# size) action = IO $ \ s0 ->
      case unsafeFreezeByteArray# mbarr# s1 of { (# s2, barr#  #) ->
      let addr = Ptr (byteArrayContents# barr#) in
      case action addr     of { IO action' ->
-     case action' s2      of { (# s3, r #) ->
-     case touch# barr# s3 of { s4 ->
-     (# s4, r #)
-  }}}}}
--- See Note [NOINLINE for touch#]
-{-# NOINLINE allocaBytes #-}
+     keepAlive# barr# s2 action'
+  }}}
 
 allocaBytesAligned :: Int -> Int -> (Ptr a -> IO b) -> IO b
 allocaBytesAligned (I# size) (I# align) action = IO $ \ s0 ->
@@ -156,12 +139,8 @@ allocaBytesAligned (I# size) (I# align) action = IO $ \ s0 ->
      case unsafeFreezeByteArray# mbarr# s1 of { (# s2, barr#  #) ->
      let addr = Ptr (byteArrayContents# barr#) in
      case action addr     of { IO action' ->
-     case action' s2      of { (# s3, r #) ->
-     case touch# barr# s3 of { s4 ->
-     (# s4, r #)
-  }}}}}
--- See Note [NOINLINE for touch#]
-{-# NOINLINE allocaBytesAligned #-}
+     keepAlive# barr# s2 action'
+  }}}
 
 -- |Resize a memory area that was allocated with 'malloc' or 'mallocBytes'
 -- to the size needed to store values of type @b@.  The returned pointer