From d3eb8cf5e3d7b1535ba73e95dee737c08a36d3bb Mon Sep 17 00:00:00 2001
From: "jan.nijtmans" <nijtmans@users.sourceforge.net>
Date: Mon, 25 May 2020 09:02:15 +0000
Subject: Fix compiled "string is <class>" for TCL_UTF_MAX=4 build, for
 characters > U+FFFF.

---
 generic/tclExecute.c |  6 ++++--
 generic/tclInt.h     |  4 +++-
 generic/tclUtf.c     | 16 ++++++++++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index eeb69de..76feb79 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -5915,9 +5915,11 @@ TEBCresume(
 	ustring1 = Tcl_GetUnicodeFromObj(valuePtr, &length);
 	match = 1;
 	if (length > 0) {
+	    int ch;
 	    end = ustring1 + length;
-	    for (p=ustring1 ; p<end ; p++) {
-		if (!tclStringClassTable[opnd].comparator(*p)) {
+	    for (p=ustring1 ; p<end ; ) {
+		p += TclUniCharToUCS4(p, &ch);
+		if (!tclStringClassTable[opnd].comparator(ch)) {
 		    match = 0;
 		    break;
 		}
diff --git a/generic/tclInt.h b/generic/tclInt.h
index b59d312..dfb3dfe 100644
--- a/generic/tclInt.h
+++ b/generic/tclInt.h
@@ -3188,8 +3188,10 @@ MODULE_SCOPE int	TclUCS4ToUtf(int, char *);
 MODULE_SCOPE int	TclUCS4ToLower(int ch);
 #if TCL_UTF_MAX == 4
     MODULE_SCOPE int	TclGetUCS4(Tcl_Obj *, int);
+    MODULE_SCOPE int	TclUniCharToUCS4(const Tcl_UniChar *, int *);
 #else
-    #define TclGetUCS4 Tcl_GetUniChar
+#   define TclGetUCS4 Tcl_GetUniChar
+#   define TclUniCharToUCS4(src, ptr) (*ptr = *(src),1)
 #endif
 
 /*
diff --git a/generic/tclUtf.c b/generic/tclUtf.c
index ed9138b..5ae977a 100644
--- a/generic/tclUtf.c
+++ b/generic/tclUtf.c
@@ -2400,6 +2400,22 @@ TclUtfToUCS4(
     *ucs4Ptr = (int)ch;
     return len;
 }
+
+#if TCL_UTF_MAX == 4
+int
+TclUniCharToUCS4(
+    const Tcl_UniChar *src,	/* The Tcl_UniChar string. */
+    int *ucs4Ptr)	/* Filled with the UCS4 codepoint represented
+			 * by the Tcl_UniChar string. */
+{
+    if (((src[0] & 0xFC00) == 0xD800) && ((src[1] & 0xFC00) == 0xDC00)) {
+	*ucs4Ptr = (((src[0] & 0x3FF) << 10) | (src[01] & 0x3FF)) + 0x10000;
+	return 2;
+    }
+    *ucs4Ptr = src[0];
+    return 1;
+}
+#endif
 
 /*
  *---------------------------------------------------------------------------
-- 
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