From ecd12fb2ff0434da5eb22ff3a0fafb93e20fdb93 Mon Sep 17 00:00:00 2001
From: Vladimir Menshakov <vladimir.menshakov@gmail.com>
Date: Tue, 10 Mar 2026 22:33:04 +0000
Subject: [PATCH] VIDEO: 4XM: fix ubsan warnings

---
 video/4xm_decoder.cpp | 19 ++++++++-----------
 video/4xm_utils.h     |  2 ++
 2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/video/4xm_decoder.cpp b/video/4xm_decoder.cpp
index 98c9a85221c..5c3cc2d0695 100644
--- a/video/4xm_decoder.cpp
+++ b/video/4xm_decoder.cpp
@@ -348,18 +348,16 @@ void mcdc(uint16_t *dst, const uint16_t *src, int log2w,
 	int h = 1 << log2h;
 	if (Scale) {
 		for (int i = 0; i < h; ++i) {
-			auto *dst32 = reinterpret_cast<uint32_t *>(dst);
-			auto *src32 = reinterpret_cast<const uint32_t *>(src);
 			switch (log2w) {
 			case 3:
-				dst32[2] = src32[2] + dc;
-				dst32[3] = src32[3] + dc;
+				WRITE_UINT32(dst + 4, READ_UINT32(src + 4) + dc);
+				WRITE_UINT32(dst + 6, READ_UINT32(src + 6) + dc);
 				// fall through
 			case 2:
-				dst32[1] = src32[1] + dc;
+				WRITE_UINT32(dst + 2, READ_UINT32(src + 2) + dc);
 				// fall through
 			case 1:
-				dst32[0] = src32[0] + dc;
+				WRITE_UINT32(dst, READ_UINT32(src) + dc);
 				break;
 			case 0:
 				*dst = *src + dc;
@@ -369,17 +367,16 @@ void mcdc(uint16_t *dst, const uint16_t *src, int log2w,
 		}
 	} else {
 		for (int i = 0; i < h; ++i) {
-			auto *dst32 = reinterpret_cast<uint32_t *>(dst);
 			switch (log2w) {
 			case 3:
-				dst32[2] = dc;
-				dst32[3] = dc;
+				WRITE_UINT32(dst + 4, dc);
+				WRITE_UINT32(dst + 6, dc);
 				// fall through
 			case 2:
-				dst32[1] = dc;
+				WRITE_UINT32(dst + 2, dc);
 				// fall through
 			case 1:
-				dst32[0] = dc;
+				WRITE_UINT32(dst, dc);
 				break;
 			case 0:
 				*dst = dc;
diff --git a/video/4xm_utils.h b/video/4xm_utils.h
index 5c6e459fe52..bd051e26460 100644
--- a/video/4xm_utils.h
+++ b/video/4xm_utils.h
@@ -54,6 +54,8 @@ HuffmanType loadStatistics(const byte *&huff, uint &offset) {
 void idct(int16_t block[64], int shift = 6);
 
 inline int readInt(int value, unsigned n) {
+	if (n == 0)
+		return 0;
 	if ((value & (1 << (n - 1))) == 0)
 		value += 1 - (1 << n);
 	return value;