[PATCH 0/1] MR920: kernel32: Map system heap anywhere if the standard address is unavailable.

[Brendan Shanks (＠bshanks)]

`mscomctl.ocx` (part of the VB6 common controls) calls `HeapCreate(0x04000000,1,0)`, that flag is the old and undocumented `HEAP_SHARED`.
`HEAP_CreateSystemHeap()` tries to map memory at `0x80000000`, this fails on Wow64 (and probably should for all 32-bit platforms for non-LAA EXEs).

As a workaround, map the memory anywhere if it fails at `0x80000000`.

I wasn't able to find much documentation about `HEAP_SHARED`, it dates back to Win9x and I guess Wine may have needed it for some native DLLs.
It's not clear whether modern Windows really implements any shared heap functionality any more, every 'shared' heap created returns a different pointer (even in the same process). Maybe Wine should remove the functionality too?

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/920

[PATCH 1/1] kernel32: Map system heap anywhere if the standard address is unavailable.

[Brendan Shanks]

From: Brendan Shanks <bshanks(a)codeweavers.com>

---
 dlls/kernel32/heap.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/dlls/kernel32/heap.c b/dlls/kernel32/heap.c
index a2910688e44..7e860748412 100644
--- a/dlls/kernel32/heap.c
+++ b/dlls/kernel32/heap.c
@@ -68,11 +68,13 @@ static inline HANDLE HEAP_CreateSystemHeap(void)
                                     0, SYSTEM_HEAP_SIZE, "__wine_system_heap" ))) return 0;
     created = (GetLastError() != ERROR_ALREADY_EXISTS);
 
-    if (!(base = MapViewOfFileEx( map, FILE_MAP_ALL_ACCESS, 0, 0, 0, SYSTEM_HEAP_BASE )))
+    base = MapViewOfFileEx( map, FILE_MAP_ALL_ACCESS, 0, 0, 0, SYSTEM_HEAP_BASE );
+    if (!base)
     {
-        /* pre-defined address not available */
-        ERR( "system heap base address %p not available\n", SYSTEM_HEAP_BASE );
-        return 0;
+        /* pre-defined address not available, map anywhere */
+        WARN( "system heap base address %p not available\n", SYSTEM_HEAP_BASE );
+	if (!(base = MapViewOfFileEx( map, FILE_MAP_ALL_ACCESS, 0, 0, 0, NULL )))
+            return 0;
     }
 
     if (created)  /* newly created heap */
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/920

[Alexandre Julliard (＠julliard)]

> Maybe Wine should remove the functionality too?

IIRC it was needed for native DCOM which we no longer support, so yes,
it could probably be removed.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/920#note_9452