From 411fc46d4f5e5e93a7d69db7f50e42b53005e343 Mon Sep 17 00:00:00 2001
From: dgp <dgp@users.sourceforge.net>
Date: Mon, 8 Nov 2021 00:06:27 +0000
Subject: [9899c273ab] Rewrite Tcl_InitStringRep to account for all encounters
 with the non-allocated empty string rep.

---
 generic/tclBinary.c  |  1 -
 generic/tclDictObj.c |  1 +
 generic/tclInt.h     |  3 ++-
 generic/tclObj.c     | 51 +++++++++++++++++++++++++++++++++------------------
 4 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/generic/tclBinary.c b/generic/tclBinary.c
index 5eb5b54..a586f18 100644
--- a/generic/tclBinary.c
+++ b/generic/tclBinary.c
@@ -842,7 +842,6 @@ UpdateStringOfByteArray(
 	for (i = 0; i < length; i++) {
 	    dst += Tcl_UniCharToUtf(src[i], dst);
 	}
-	(void) Tcl_InitStringRep(objPtr, NULL, size);
     }
 }
 
diff --git a/generic/tclDictObj.c b/generic/tclDictObj.c
index 900974f..b4249b8 100644
--- a/generic/tclDictObj.c
+++ b/generic/tclDictObj.c
@@ -566,6 +566,7 @@ UpdateStringOfDict(
 	dst += TclConvertElement(elem, length, dst, flagPtr[i+1]);
 	*dst++ = ' ';
     }
+    /* Last space overwrote the terminating NUL; cal T_ISR again to restore */
     (void)Tcl_InitStringRep(dictPtr, NULL, bytesNeeded - 1);
 
     if (flagPtr != localFlags) {
diff --git a/generic/tclInt.h b/generic/tclInt.h
index 03d005a..7b03502 100644
--- a/generic/tclInt.h
+++ b/generic/tclInt.h
@@ -4492,7 +4492,8 @@ MODULE_SCOPE void	TclDbInitNewObj(Tcl_Obj *objPtr, const char *file,
  * must point to a location from which "len" bytes may be read.  These
  * constraints are not checked here.  The validity of the bytes copied
  * as a value string representation is also not verififed.  This macro
- * must not be called while "objPtr" is being freed.  The caller must use
+ * must not be called while "objPtr" is being freed or when "objPtr"
+ * already has a string representation.  The caller must use
  * this macro properly.  Improper use can lead to dangerous results.
  * Because "len" is referenced multiple times, take care that it is an
  * expression with the same value each use. 
diff --git a/generic/tclObj.c b/generic/tclObj.c
index e5ec838..92c6655 100644
--- a/generic/tclObj.c
+++ b/generic/tclObj.c
@@ -1815,32 +1815,48 @@ Tcl_InitStringRep(
 	Tcl_Panic("max size for a Tcl value (%d bytes) exceeded", INT_MAX);
     }
 
-    /* Allocate */
     if (objPtr->bytes == NULL) {
-	/* Allocate only as empty - extend later if bytes copied */
-	objPtr->length = 0;
-	if (numBytes) {
+	/* Start with no string rep */
+	if (numBytes == 0) {
+	    TclInitStringRep(objPtr, NULL, 0);
+	    return objPtr->bytes;
+	} else {
 	    objPtr->bytes = (char *)attemptckalloc(numBytes + 1);
-	    if (objPtr->bytes == NULL) {
-		return NULL;
-	    }
-	    if (bytes) {
-		/* Copy */
-		memcpy(objPtr->bytes, bytes, numBytes);
+	    if (objPtr->bytes) {
 		objPtr->length = (int) numBytes;
+		if (bytes) {
+		    memcpy(objPtr->bytes, bytes, numBytes);
+		}
+		objPtr->bytes[objPtr->length] = '\0';
 	    }
+	}
+    } else if (objPtr->bytes == &tclEmptyString) {
+	/* Start with empty string rep (not allocated) */
+	if (numBytes == 0) {
+	    return objPtr->bytes;
 	} else {
-	    TclInitStringRep(objPtr, NULL, 0);
+	    objPtr->bytes = (char *)attemptckalloc(numBytes + 1);
+	    if (objPtr->bytes) {
+		objPtr->length = (int) numBytes;
+		objPtr->bytes[objPtr->length] = '\0';
+	    }
 	}
     } else {
-	/* objPtr->bytes != NULL bytes == NULL - Truncate */
-	objPtr->bytes = (char *)ckrealloc(objPtr->bytes, numBytes + 1);
-	objPtr->length = (int)numBytes;
+	/* Start with non-empty string rep (allocated) */
+	if (numBytes == 0) {
+	    ckfree(objPtr->bytes);
+	    TclInitStringRep(objPtr, NULL, 0);
+	    return objPtr->bytes;
+	} else {
+	    objPtr->bytes = (char *)attemptckrealloc(objPtr->bytes,
+		    numBytes + 1);
+	    if (objPtr->bytes) {
+		objPtr->length = (int) numBytes;
+		objPtr->bytes[objPtr->length] = '\0';
+	    }
+	}
     }
 
-    /* Terminate */
-    objPtr->bytes[objPtr->length] = '\0';
-
     return objPtr->bytes;
 }
 
@@ -3517,7 +3533,6 @@ UpdateStringOfBignum(
     if (MP_OKAY != mp_to_radix(&bignumVal, stringVal, size, NULL, 10)) {
 	Tcl_Panic("conversion failure in UpdateStringOfBignum");
     }
-    (void) Tcl_InitStringRep(objPtr, NULL, size - 1);
 }
 
 /*
-- 
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