[Bf-blender-cvs] [c8103efbe3b] blender-v2.82-release: Fix undefined behavior in tangent space computation
Simon G
noreply at git.blender.org
Mon Jan 27 18:01:58 CET 2020
Commit: c8103efbe3bfa2487a2866a7cf22e3b7681338ef
Author: Simon G
Date: Mon Jan 27 17:53:49 2020 +0100
Branches: blender-v2.82-release
https://developer.blender.org/rBc8103efbe3bfa2487a2866a7cf22e3b7681338ef
Fix undefined behavior in tangent space computation
Use an improved implementation for circular shift.
Differential Revision: https://developer.blender.org/D6677
===================================================================
M intern/mikktspace/mikktspace.c
===================================================================
diff --git a/intern/mikktspace/mikktspace.c b/intern/mikktspace/mikktspace.c
index 4f120b7d83c..285529298eb 100644
--- a/intern/mikktspace/mikktspace.c
+++ b/intern/mikktspace/mikktspace.c
@@ -27,6 +27,7 @@
#include <string.h>
#include <float.h>
#include <stdlib.h>
+#include <limits.h>
#include "mikktspace.h"
@@ -135,6 +136,17 @@ MIKK_INLINE tbool VNotZero(const SVec3 v)
}
#endif
+// Shift operations in C are only defined for shift values which are
+// not negative and smaller than sizeof(value) * CHAR_BIT.
+// The mask, used with bitwise-and (&), prevents undefined behaviour
+// when the shift count is 0 or >= the width of unsigned int.
+MIKK_INLINE unsigned int rotl(unsigned int value, unsigned int count)
+{
+ const unsigned int mask = CHAR_BIT * sizeof(value) - 1;
+ count &= mask;
+ return (value << count) | (value >> (-count & mask));
+}
+
typedef struct {
int iNrFaces;
int *pTriMembers;
@@ -1605,7 +1617,7 @@ static void QuickSortEdges(
// Random
t = uSeed & 31;
- t = (uSeed << t) | (uSeed >> (32 - t));
+ t = rotl(uSeed, t);
uSeed = uSeed + t + 3;
// Random end
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