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.

2 files changed, 13 insertions, 9 deletions

diff --git a/rts/HeapStackCheck.cmm b/rts/HeapStackCheck.cmm
index f8195768fb..d17961145a 100644
--- a/rts/HeapStackCheck.cmm
+++ b/rts/HeapStackCheck.cmm
@@ -662,24 +662,24 @@ stg_block_throwto
 }
 
 #ifdef mingw32_HOST_OS
-INFO_TABLE_RET( stg_block_async, RET_SMALL )
+INFO_TABLE_RET( stg_block_async, RET_SMALL, W_ unused )
 {
     W_ ares;
     W_ len, errC;
 
-    ares = StgTSO_block_info(CurrentTSO);
+    ares = Sp(1);
     len = StgAsyncIOResult_len(ares);
     errC = StgAsyncIOResult_errCode(ares);
-    StgTSO_block_info(CurrentTSO) = NULL;
     foreign "C" free(ares "ptr");
     R1 = len;
+    Sp_adj(1);
     Sp(0) = errC;
     jump %ENTRY_CODE(Sp(1));
 }
 
 stg_block_async
 {
-    Sp_adj(-1);
+    Sp_adj(-2);
     Sp(0) = stg_block_async_info;
     BLOCK_GENERIC;
 }
@@ -687,20 +687,19 @@ stg_block_async
 /* Used by threadDelay implementation; it would be desirable to get rid of
  * this free()'ing void return continuation.
  */
-INFO_TABLE_RET( stg_block_async_void, RET_SMALL )
+INFO_TABLE_RET( stg_block_async_void, RET_SMALL, W_ ares )
 {
     W_ ares;
 
-    ares = StgTSO_block_info(CurrentTSO);
-    StgTSO_block_info(CurrentTSO) = NULL;
+    ares = Sp(1);
     foreign "C" free(ares "ptr");
-    Sp_adj(1);
+    Sp_adj(2);
     jump %ENTRY_CODE(Sp(0));
 }
 
 stg_block_async_void
 {
-    Sp_adj(-1);
+    Sp_adj(-2);
     Sp(0) = stg_block_async_void_info;
     BLOCK_GENERIC;
 }
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;
 		    }