ghc-heap: Decode StgStack and its stack frameswip/decode_cloned_stack

Previously, ghc-heap could only decode heap closures.

The approach is explained in detail in note
[Decoding the stack].

1 files changed, 49 insertions, 0 deletions

diff --git a/libraries/ghc-heap/tests/stack_underflow.hs b/libraries/ghc-heap/tests/stack_underflow.hs
new file mode 100644
index 0000000000..7da5fb1d34
--- /dev/null
+++ b/libraries/ghc-heap/tests/stack_underflow.hs
@@ -0,0 +1,49 @@
+{-# LANGUAGE RecordWildCards #-}
+
+module Main where
+
+import Control.Monad
+import Data.Bool (Bool (True))
+import GHC.Exts.Heap
+import GHC.Exts.Heap.ClosureTypes
+import GHC.Exts.Heap.Closures
+import GHC.Exts.Heap.InfoTable.Types
+import GHC.Exts.Stack.Decode
+import GHC.Stack (HasCallStack)
+import GHC.Stack.CloneStack
+import TestUtils
+
+main = loop 256
+
+{-# NOINLINE loop #-}
+loop 0 = Control.Monad.void getStack
+loop n = print "x" >> loop (n - 1) >> print "x"
+
+getStack :: HasCallStack => IO ()
+getStack = do
+  (s, decodedStack) <- getDecodedStack
+  assertStackInvariants decodedStack
+  assertThat
+    "Stack contains underflow frames"
+    (== True)
+    (any isUnderflowFrame decodedStack)
+  assertStackChunksAreDecodable decodedStack
+  return ()
+
+isUnderflowFrame :: StackFrame -> Bool
+isUnderflowFrame (UnderflowFrame {..}) = tipe info_tbl == UNDERFLOW_FRAME
+isUnderflowFrame _ = False
+
+assertStackChunksAreDecodable :: HasCallStack => [StackFrame] -> IO ()
+assertStackChunksAreDecodable s = do
+  let underflowFrames = filter isUnderflowFrame s
+  assertThat
+    ("Expect some underflow frames. Got " ++ show (length underflowFrames))
+    (>= 2)
+    (length underflowFrames)
+  let stackFrames = map (ssc_stack . nextChunk) underflowFrames
+  assertThat
+    "No empty stack chunks"
+    (== True)
+    ( not (any null stackFrames)
+    )