Harden _WhoControlsSquareFast against g_SwapTable out-of-bounds indexing

Add ASSERT(uWhite < 32)/ASSERT(uBlack < 32), the bound that actually
matters for g_SwapTable[14][32][32] -- the existing (& 0xFFFFFF00)
checks only caught garbage above bit 7 and would have passed silently
through the exact out-of-bounds indexing fixed in the previous commit,
had a similar bit-layout mistake been made again in the future.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01XxmVi2sTMwpPp4i6WYFjan

1 files changed, 10 insertions, 0 deletions

diff --git a/src/eval.c b/src/eval.c
index eb6e118..63fd301 100755
--- a/src/eval.c
+++ b/src/eval.c
@@ -1149,6 +1149,16 @@ Return value:
     PIECE p;
     CHAR ch;
 
+    // g_SwapTable is only [14][32][32] (data.c) -- this is the bound
+    // that actually matters, not just "no garbage above bit 7" below.
+    // PAWN_BIT..KING_BIT briefly didn't fit in bits 0-4 earlier this
+    // session (when _WhoControlsSquareFast was converted to read them
+    // directly instead of going through the old ATTACK_BITV struct)
+    // and silently indexed out of bounds on every attacked square --
+    // the (& 0xFFFFFF00) checks below never caught it (board_
+    // representation/EVAL.md section 9).
+    ASSERT(uWhite < 32);
+    ASSERT(uBlack < 32);
     ASSERT((uWhite & 0xFFFFFF00) == 0);
     ASSERT((uBlack & 0xFFFFFF00) == 0);