From: Stefan Reinauer <stefan.reinauer@coreboot.org>
Date: Thu, 21 May 2026 00:37:36 +0000 (-0700)
Subject: isofs: avoid undefined timezone sign extension
X-Git-Url: https://git.unchartedbackwaters.co.uk/w/?a=commitdiff_plain;h=17c59f8f683050453f2338fea691131c6584d14c;p=francis%2Fwinuae.git

isofs: avoid undefined timezone sign extension

make_date() sign-extends the ISO9660 timezone byte when the high
bit is set. (-1 << 8) shifts a negative signed value, which is
undefined behavior in C++.

Use ~0xff to build the same extension mask without relying on
that undefined shift.
---

diff --git a/isofs.cpp b/isofs.cpp
index d40bd1b9..5fb47a30 100644
--- a/isofs.cpp
+++ b/isofs.cpp
@@ -328,7 +328,7 @@ static int make_date(int year, int month, int day, int hour, int minute, int sec
 
 		/* sign extend */
 		if (tz & 0x80)
-			tz |= (-1 << 8);
+			tz |= ~0xff;
 		
 		/* 
 		 * The timezone offset is unreliable on some disks,