Blackholes can be large objects (#14497)

Test Plan: validate

Reviewers: bgamari, niteria, erikd, dfeuer

Reviewed By: dfeuer

Subscribers: Yuras, dfeuer, rwbarton, thomie, carter

GHC Trac Issues: #14497

Differential Revision: https://phabricator.haskell.org/D4254

rts/sm/Evac.c

@@ -898,9 +898,16 @@ evacuate_BLACKHOLE(StgClosure **p)
 
     bd = Bdescr((P_)q);
 
-    // blackholes can't be in a compact, or large
-    ASSERT((bd->flags & (BF_COMPACT | BF_LARGE)) == 0);
-
+    // blackholes can't be in a compact
+    ASSERT((bd->flags & BF_COMPACT) == 0);
+
+    // blackholes *can* be in a large object: when raiseAsync() creates an
+    // AP_STACK the payload might be large enough to create a large object.
+    // See #14497.
+    if (bd->flags & BF_LARGE) {
+        evacuate_large((P_)q);
+        return;
+    }
     if (bd->flags & BF_EVACUATED) {
         if (bd->gen_no < gct->evac_gen_no) {
             gct->failed_to_evac = true;

testsuite/tests/rts/T14497.hs

+module Main (main) where
+
+import System.Timeout
+
+fuc :: Integer -> Integer
+fuc 0 = 1
+fuc n = n * fuc (n - 1)
+
+main :: IO ()
+main = do
+  let x = fuc 30000
+  timeout 1000 (print x)
+  print (x > 0)

testsuite/tests/rts/T14497.stdout

+True

testsuite/tests/rts/all.T

@@ -381,3 +381,4 @@ test('T12497', [ unless(opsys('mingw32'), skip)
 test('T12903', [when(opsys('mingw32'), skip)], compile_and_run, [''])
 test('T13832', exit_code(1), compile_and_run, ['-threaded'])
 test('T13894', normal, compile_and_run, [''])
+test('T14497', normal, compile_and_run, ['-O'])