Fix crash in non-threaded RTS on Windows

The tso->block_info field is now overwritten by pushOnRunQueue(), but
stg_block_async_info was assuming that it still held a pointer to the
StgAsyncIOResult.  We must therefore save this value somewhere safe
before putting the TSO on the run queue.

1 files changed, 5 insertions, 0 deletions

diff --git a/rts/win32/AsyncIO.c b/rts/win32/AsyncIO.c
index 8662e2a369..5dedee0c70 100644
--- a/rts/win32/AsyncIO.c
+++ b/rts/win32/AsyncIO.c
@@ -313,6 +313,11 @@ start:
 			/* Terminates the run queue + this inner for-loop. */
 			tso->_link = END_TSO_QUEUE;
 			tso->why_blocked = NotBlocked;
+                        // save the StgAsyncIOResult in the
+                        // stg_block_async_info stack frame, because
+                        // the block_info field will be overwritten by
+                        // pushOnRunQueue().
+                        tso->sp[1] = (W_)tso->block_info.async_result;
 			pushOnRunQueue(&MainCapability, tso);
 			break;
 		    }