Guard against UB in lsb/msb

[stockfish] / src / bitboard.cpp

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 47dce42eabb55315ff36bf325f90f28e53fc10e3..ba1af2f2865f28865791178206add9752a392889 100644 (file)
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -76,16 +76,18 @@ namespace {
   }
 }
 
-#ifndef USE_BSFQ
+#ifdef NO_BSF
 
 /// Software fall-back of lsb() and msb() for CPU lacking hardware support
 
 Square lsb(Bitboard b) {
+  assert(b);
   return BSFTable[bsf_index(b)];
 }
 
 Square msb(Bitboard b) {
 
+  assert(b);
   unsigned b32;
   int result = 0;
 
@@ -112,7 +114,7 @@ Square msb(Bitboard b) {
   return Square(result + MSBTable[b32]);
 }
 
-#endif // ifndef USE_BSFQ
+#endif // ifdef NO_BSF
 
 
 /// Bitboards::pretty() returns an ASCII representation of a bitboard suitable