From 3ec501f29bdd63cb4b75f5b369d2c24505b3a6ee Mon Sep 17 00:00:00 2001
From: dgp <dgp@users.sourceforge.net>
Date: Thu, 7 May 2020 20:31:48 +0000
Subject: Same trouble with Tcl_UtfToUniCharDstring. Test and fix.

---
 generic/tclUtf.c |  9 +++++----
 tests/utf.test   | 11 ++++++++++-
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/generic/tclUtf.c b/generic/tclUtf.c
index 80f3be8..7309208 100644
--- a/generic/tclUtf.c
+++ b/generic/tclUtf.c
@@ -453,11 +453,12 @@ Tcl_UtfToUniCharDString(
 	p += TclUtfToUniChar(p, w);
 	w++;
     }
-    while ((p < endPtr) && Tcl_UtfCharComplete(p, endPtr-p)) {
-	p += TclUtfToUniChar(p, w++);
-    }
     while (p < endPtr) {
-	*w++ = UCHAR(*p++);
+	if (Tcl_UtfCharComplete(p, endPtr-p)) {
+	    p += TclUtfToUniChar(p, w++);
+	} else {
+	    *w++ = UCHAR(*p++);
+	}
     }
     *w = '\0';
     Tcl_DStringSetLength(dsPtr,
diff --git a/tests/utf.test b/tests/utf.test
index f48299d..5300328 100644
--- a/tests/utf.test
+++ b/tests/utf.test
@@ -1473,7 +1473,16 @@ UniCharCaseCmpTest > [format %c 0x10000] \uFFFF	ucs4
 UniCharCaseCmpTest > \U10000 \uFFFF		{Uesc ucs4}
 
 
-
+test utf-26.1 {Tcl_UniCharDString} -setup {
+    testobj freeallvars
+} -constraints {teststringobj} -cleanup {
+    testobj freeallvars
+} -body {
+    teststringobj set 1 foo
+    teststringobj getunicode 1
+    teststringobj append 1 [testbytestring barsoom\xF2\xC2\x80] 10
+    scan [string index [teststringobj get 1] 11] %c
+} -result 128
 
 
 unset count
-- 
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