From 552ef1ca02c0b71c2c1cda3d1330a4fabc93b3c1 Mon Sep 17 00:00:00 2001
From: sebres <sebres@users.sourceforge.net>
Date: Tue, 5 Dec 2023 22:42:02 +0000
Subject: closes [db4f2843cd]: fixes SF by BO in ReadChars (and Tcl_ReadChars
 with append) caused by wrong buffer enlarge if objPtr shimmering to unicode
 for whatever reason, since Tcl_AppendToObj prefers unicode to bytes, whereas
 Tcl_SetObjLength prefers bytes (like the ReadChars)

---
 generic/tclIO.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/generic/tclIO.c b/generic/tclIO.c
index 0f79f1e..0153646 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -6112,7 +6112,7 @@ ReadChars(
     int dstLimit = TCL_UTF_MAX - 1 + toRead * factor / UTF_EXPANSION_FACTOR;
 
     (void) TclGetStringFromObj(objPtr, &numBytes);
-    Tcl_AppendToObj(objPtr, NULL, dstLimit);
+    Tcl_SetObjLength(objPtr, numBytes + dstLimit);
     if (toRead == srcLen) {
 	unsigned int size;
 
-- 
cgit v0.12