From df0ddd7b9b44266ea375ae17eec07ebb21c1157c Mon Sep 17 00:00:00 2001
From: pooryorick <com.digitalsmarties@pooryorick.com>
Date: Tue, 18 Apr 2023 22:00:10 +0000
Subject: Fix for [25cdcb7e8fb381fb]:  Incomplete utf-8 sequence followed by
 eofchar results in failed assertion.

---
 generic/tclIO.c |  7 ++++++-
 tests/io.test   | 34 ++++++++++++++++++++++++++++++----
 2 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/generic/tclIO.c b/generic/tclIO.c
index 36ae16e..bf28508 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -6310,7 +6310,12 @@ ReadChars(
 		flags, &statePtr->inputEncodingState,
 		dst, dstLimit, &srcRead, &dstDecoded, &numChars);
 
-	if (code == TCL_CONVERT_UNKNOWN || code == TCL_CONVERT_SYNTAX) {
+	if (code == TCL_CONVERT_UNKNOWN || code == TCL_CONVERT_SYNTAX
+	    || (
+		code == TCL_CONVERT_MULTIBYTE
+		&& GotFlag(statePtr, CHANNEL_EOF
+	    ))
+	) {
 	    SetFlag(statePtr, CHANNEL_ENCODING_ERROR);
 	    code = TCL_OK;
 	}
diff --git a/tests/io.test b/tests/io.test
index 3ab09e8..dfa015f 100644
--- a/tests/io.test
+++ b/tests/io.test
@@ -9326,25 +9326,51 @@ test io-75.8.eoflater {invalid utf-8 encoding eof handling (-profile strict)} -s
 	set res {}
     set fn [makeFile {} io-75.8]
     set f [open $fn w+]
+    # This also configures the channel encoding profile as strict.
     fconfigure $f -encoding binary
     # \x81 is invalid in utf-8. -eofchar is not detected, because it comes later.
-    puts -nonewline $f A\x81\x1A
+    puts -nonewline $f A\x81\x81\x1A
     flush $f
     seek $f 0
     fconfigure $f -encoding utf-8 -buffering none -eofchar \x1A \
 	-translation lf -profile strict
 } -body {
-    after 1
     set status [catch {read $f} cres copts]
     lappend res $status
     lappend res [eof $f]
     chan configure $f -encoding iso8859-1
-    lappend res [read $f]
+    lappend res [read $f 1]
+    chan configure $f -encoding utf-8
+    catch {read $f 1} cres
+    lappend res $cres
     close $f
     set res
 } -cleanup {
     removeFile io-75.8
-} -result "1 0 \x81"
+} -match glob -result "1 0 \x81 {error reading \"*\":\
+    invalid or incomplete multibyte or wide character}"
+
+
+test io-strict-multibyte-eof {
+    incomplete utf-8 sequence immediately prior to eof character
+
+    See issue 25cdcb7e8fb381fb
+} -setup {
+    set res {}
+    set chan [file tempfile];
+    fconfigure $chan -encoding binary
+    puts -nonewline $chan \x81\x1A
+    flush $chan
+    seek $chan 0
+    chan configure $chan -encoding utf-8 -profile strict
+} -body {
+    set status [catch {read $chan 1} cres]
+    lappend res $status $cres
+} -cleanup {
+    close $chan
+    unset res
+} -match glob -result {1 {error reading "*":\
+    invalid or incomplete multibyte or wide character}}
 
 test io-75.9 {unrepresentable character write passes and is replaced by ?} -setup {
     set fn [makeFile {} io-75.9]
-- 
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