[commit: ghc] master: Fix nptr field alignment in RtClosureInspect (15bb4e0)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/15bb4e0b6c08b1f8f5511f04af14242f13833ed1/ghc

>---------------------------------------------------------------

commit 15bb4e0b6c08b1f8f5511f04af14242f13833ed1
Author: Ömer Sinan Ağacan <omeragacan at gmail.com>
Date:   Wed Jul 4 09:12:01 2018 +0300

    Fix nptr field alignment in RtClosureInspect
    
    `extractSubTerms` (which is extracting pointer and non-pointer fields of a
    closure) was computing the alignment incorrectly when aligning a 64-bit value
    (e.g. a Double) on i386 by aligning it to 64-bits instead of to word size
    (32-bits). This is documented in `mkVirtHeapOffsetsWithPadding`:
    
    > Align the start offset (eg, 2-byte value should be 2-byte aligned).
    > But not more than to a word.
    
    Fixes #15061
    
    Test Plan:
    Validated on both 32-bit and 64-bit. 32-bit fails with various unrelated stat
    failures, but no actual test failures.
    
    Reviewers: hvr, bgamari
    
    Reviewed By: bgamari
    
    Subscribers: simonpj, rwbarton, thomie, carter
    
    GHC Trac Issues: #15061
    
    Differential Revision: https://phabricator.haskell.org/D4906


>---------------------------------------------------------------

15bb4e0b6c08b1f8f5511f04af14242f13833ed1
 compiler/ghci/RtClosureInspect.hs           | 11 +++++++----
 testsuite/tests/ghci.debugger/scripts/all.T |  3 +--
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/compiler/ghci/RtClosureInspect.hs b/compiler/ghci/RtClosureInspect.hs
index 81bdb61..d540983 100644
--- a/compiler/ghci/RtClosureInspect.hs
+++ b/compiler/ghci/RtClosureInspect.hs
@@ -742,11 +742,14 @@ extractSubTerms recurse clos = liftM thdOf3 . go 0 0
           dflags <- getDynFlags
           let word_size = wORD_SIZE dflags
               size_b = primRepSizeB dflags rep
-              -- Fields are always aligned.
-              !aligned_idx = roundUpTo arr_i size_b
+              -- Align the start offset (eg, 2-byte value should be 2-byte
+              -- aligned). But not more than to a word. The offset calculation
+              -- should be the same with the offset calculation in
+              -- StgCmmLayout.mkVirtHeapOffsetsWithPadding.
+              !aligned_idx = roundUpTo arr_i (min word_size size_b)
               !new_arr_i = aligned_idx + size_b
               ws | size_b < word_size =
-                     [index size_b array aligned_idx word_size]
+                     [index size_b aligned_idx word_size]
                  | otherwise =
                      let (q, r) = size_b `quotRem` word_size
                      in ASSERT( r == 0 )
@@ -761,7 +764,7 @@ extractSubTerms recurse clos = liftM thdOf3 . go 0 0
                 (error "unboxedTupleTerm: no HValue for unboxed tuple") terms
 
     -- Extract a sub-word sized field from a word
-    index item_size_b array index_b word_size =
+    index item_size_b index_b word_size =
         (word .&. (mask `shiftL` moveBytes)) `shiftR` moveBytes
       where
         mask :: Word
diff --git a/testsuite/tests/ghci.debugger/scripts/all.T b/testsuite/tests/ghci.debugger/scripts/all.T
index 88acdb0..f2e2658 100644
--- a/testsuite/tests/ghci.debugger/scripts/all.T
+++ b/testsuite/tests/ghci.debugger/scripts/all.T
@@ -22,8 +22,7 @@ test('print019', extra_files(['../Test.hs']), ghci_script, ['print019.script'])
 test('print020', extra_files(['../HappyTest.hs']), ghci_script, ['print020.script'])
 test('print021', normal, ghci_script, ['print021.script'])
 test('print022',
-     [when(arch('powerpc64'), expect_broken(14455)),
-      when(wordsize(32), expect_broken(15061))],
+     [when(arch('powerpc64'), expect_broken(14455))],
      ghci_script, ['print022.script'])
 test('print023', extra_files(['../Test.hs']), ghci_script, ['print023.script'])
 test('print024', extra_files(['../Test.hs']), ghci_script, ['print024.script'])