randr: fix broken macros / memory corruption

By casting the rrScrPriv to ScreenPtr we are using the offsets from the Screen structure for referencing data in the rrScrPriv structure causing data corruption. As both macros use the same casting this still works until the location where the data resides is overwritten. For 64bit the location was the "rotations" member in rrScrPriv which was not problematic because it is barely used. But on 32bit it was "numCrtcs" which is heavily used. On unwrap this was 0 and lead to a segfault. Fixes ArcticaProject/nx-libs#943

randr: fix broken macros / memory corruption
d1a967f3 · Ulrich Sibiller · 67330d9e · d1a967f3
Commit d1a967f3 authored Oct 16, 2020 by Ulrich Sibiller
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randr.c nx-X11/programs/Xserver/randr/randr.c +3 -3

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--- a/nx-X11/programs/Xserver/randr/randr.c
+++ b/nx-X11/programs/Xserver/randr/randr.c
@@ -69,12 +69,12 @@
 static int RRNScreens;

 #define wrap(priv,real,mem,func) {\
-    ((ScreenPtr)priv)->mem = ((ScreenPtr)real)->mem; \
-    ((ScreenPtr)real)->mem = func; \
+    priv->mem = real->mem; \
+    real->mem = func; \
 }

 #define unwrap(priv,real,mem) {\
-    ((ScreenPtr)real)->mem = ((ScreenPtr)priv)->mem; \
+    real->mem = priv->mem; \
 }

 static int ProcRRDispatch(ClientPtr pClient);