From: Pádraig Brady <P@draigBrady.com>
Date: Wed, 4 Mar 2026 16:56:48 +0000 (+0000)
Subject: fold: fix output truncation with 0xFF bytes in input
X-Git-Tag: v9.11~195
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=a85e9182b1d173c26205dada54133cd9e9174fc1;p=thirdparty%2Fcoreutils.git

fold: fix output truncation with 0xFF bytes in input

On signed char platforms, 0xFF was converted to -1
which matches MBBUF_EOF, causing fold to stop processing.

* NEWS: Mention the bug fix.
* gl/lib/mbbuf.h: Avoid sign extension on signed char platforms.
* tests/fold/fold-characters.sh: Adjust test case.
Reported at https://src.fedoraproject.org/rpms/coreutils/pull-request/20
---

diff --git a/NEWS b/NEWS
index 7eb70b6d15..340115eccf 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,9 @@ GNU coreutils NEWS                                    -*- outline -*-
 
 ** Bug fixes
 
+  'fold' will no longer truncate output when encountering 0xFF bytes.
+  [bug introduced in coreutils-9.8]
+
   'kill --help' now has links to valid anchors in the html manual.
   [bug introduced in coreutils-9.10]
 
diff --git a/gl/lib/mbbuf.h b/gl/lib/mbbuf.h
index 9054fc92e0..ea4b7e7087 100644
--- a/gl/lib/mbbuf.h
+++ b/gl/lib/mbbuf.h
@@ -96,7 +96,7 @@ mbbuf_get_char (mbbuf_t *mbbuf)
   else
     {
       /* Assume the program will emit the byte, but keep the error flag.  */
-      g.ch = mbbuf->buffer[mbbuf->offset++];
+      g.ch = (unsigned char) mbbuf->buffer[mbbuf->offset++];
     }
   return g;
 }
diff --git a/tests/fold/fold-characters.sh b/tests/fold/fold-characters.sh
index b44276eaa7..5af9856f65 100755
--- a/tests/fold/fold-characters.sh
+++ b/tests/fold/fold-characters.sh
@@ -87,11 +87,12 @@ compare exp3 out3 || fail=1
 bad_unicode_with_nul ()
 {
   # invalid UTF8|unpaired surrogate|NUL|C1 control|noncharacter
-  env printf '\xC3|\xED\xBA\xAD|\u0000|\u0089|\xED\xA6\xBF\xED\xBF\xBF\n'
+  env printf '\xFF|\xED\xBA\xAD|\u0000|\u0089|\xED\xA6\xBF\xED\xBF\xBF\n'
 }
-bad_unicode_with_nul > /dev/null || framework_failure_
-test $({ bad_unicode_with_nul | fold; \
-         bad_unicode_with_nul; } | uniq | wc -l) = 1 || fail=1
+bad_unicode_with_nul > exp4 || framework_failure_
+bad_unicode_with_nul | fold > out4 || fail=1
+compare exp4 out4 || fail=1
+
 # Check bad character at EOF
 test $(env printf '\xC3' | fold | wc -c) = 1 || fail=1