Merge 8.7

2 files changed, 13 insertions, 11 deletions

diff --git a/doc/Utf.3 b/doc/Utf.3
index a7f60d2..26207ba 100644
--- a/doc/Utf.3
+++ b/doc/Utf.3
@@ -283,7 +283,8 @@ byte \fIsrc[0]\fR nor the byte \fIstart[-1]\fR nor the byte
 Pascal Ord() function.  It returns the Unicode character represented at the
 specified character (not byte) \fIindex\fR in the UTF-8 string
 \fIsrc\fR.  The source string must contain at least \fIindex\fR
-characters.
+characters.  If \fIindex\fR is TCL_INDEX_NONE or \fIindex\fR points
+to the second half of a surrogate pair, it returns -1.
 .PP
 \fBTcl_UtfAtIndex\fR returns a pointer to the specified character (not
 byte) \fIindex\fR in the UTF-8 string \fIsrc\fR.  The source string must
diff --git a/generic/tclUtf.c b/generic/tclUtf.c
index 74e7888..fde80ae 100644
--- a/generic/tclUtf.c
+++ b/generic/tclUtf.c
@@ -1146,18 +1146,19 @@ Tcl_UniCharAtIndex(
     Tcl_UniChar ch = 0;
     int i = 0;
 
-    if (index != TCL_INDEX_NONE) {
-	while (index--) {
-	    i = TclUtfToUniChar(src, &ch);
-	    src += i;
-	}
+    if (index == TCL_INDEX_NONE) {
+	return -1;
+    }
+    while (index--) {
+	i = TclUtfToUniChar(src, &ch);
+	src += i;
+    }
 #if TCL_UTF_MAX <= 3
-	if ((ch >= 0xD800) && (i < 3)) {
-	    /* Index points at character following high Surrogate */
-	    return -1;
-	}
-#endif
+    if ((ch >= 0xD800) && (i < 3)) {
+	/* Index points at character following high Surrogate */
+	return -1;
     }
+#endif
     TclUtfToUCS4(src, &i);
     return i;
 }