From c3bcd951b8dd8bf57202915b9d914bcddc73b9bb Mon Sep 17 00:00:00 2001
From: "jan.nijtmans" <nijtmans@users.sourceforge.net>
Date: Mon, 17 Jan 2022 17:26:37 +0000
Subject: Possible fix for [e9a2715d91]: Tcl 8.6.11: Incompatible
 Tcl_GetRange()

---
 generic/tclCmdMZ.c     | 14 ++++++++++----
 generic/tclExecute.c   | 15 +++++++++++----
 generic/tclStringObj.c | 12 ++++++++----
 generic/tclTest.c      |  2 +-
 4 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/generic/tclCmdMZ.c b/generic/tclCmdMZ.c
index 5422b7f..bf75d44 100644
--- a/generic/tclCmdMZ.c
+++ b/generic/tclCmdMZ.c
@@ -395,9 +395,13 @@ Tcl_RegexpObjCmd(
 		newPtr = Tcl_NewListObj(2, objs);
 	    } else {
 		if (i <= info.nsubs) {
-		    newPtr = Tcl_GetRange(objPtr,
-			    offset + info.matches[i].start,
-			    offset + info.matches[i].end - 1);
+		    if (info.matches[i].end <= 0) {
+			TclNewObj(newPtr);
+		    } else {
+			newPtr = Tcl_GetRange(objPtr,
+				offset + info.matches[i].start,
+				offset + info.matches[i].end - 1);
+		    }
 		} else {
 		    TclNewObj(newPtr);
 		}
@@ -2183,7 +2187,9 @@ StringRangeCmd(
 	return TCL_ERROR;
     }
 
-    Tcl_SetObjResult(interp, Tcl_GetRange(objv[1], first, last));
+    if (last >= 0) {
+	Tcl_SetObjResult(interp, Tcl_GetRange(objv[1], first, last));
+    }
     return TCL_OK;
 }
 
diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index c39bc21..a3b0401 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -5609,7 +5609,11 @@ TEBCresume(
 	    goto gotError;
 	}
 
-	objResultPtr = Tcl_GetRange(OBJ_AT_DEPTH(2), fromIdx, toIdx);
+	if (toIdx < 0) {
+	    TclNewObj(objResultPtr);
+	} else {
+	    objResultPtr = Tcl_GetRange(OBJ_AT_DEPTH(2), fromIdx, toIdx);
+	}
 	TRACE_APPEND(("\"%.30s\"\n", O2S(objResultPtr)));
 	NEXT_INST_V(1, 3, 1);
 
@@ -5653,11 +5657,14 @@ TEBCresume(
 	    fromIdx = TCL_INDEX_START;
 	}
 	if (fromIdx == TCL_INDEX_AFTER) {
+	    goto emptyRange;
+	}
+	fromIdx = TclIndexDecode(fromIdx, length - 1);
+	if (toIdx >= 0) {
+	    objResultPtr = Tcl_GetRange(valuePtr, fromIdx, toIdx);
+	} else {
 	emptyRange:
 	    TclNewObj(objResultPtr);
-	} else {
-	    fromIdx = TclIndexDecode(fromIdx, length - 1);
-	    objResultPtr = Tcl_GetRange(valuePtr, fromIdx, toIdx);
 	}
 	TRACE_APPEND(("%.30s\n", O2S(objResultPtr)));
 	NEXT_INST_F(9, 1, 1);
diff --git a/generic/tclStringObj.c b/generic/tclStringObj.c
index 756b948..b4f05dd 100644
--- a/generic/tclStringObj.c
+++ b/generic/tclStringObj.c
@@ -772,7 +772,7 @@ Tcl_GetRange(
     if (TclIsPureByteArray(objPtr)) {
 	unsigned char *bytes = Tcl_GetByteArrayFromObj(objPtr, &length);
 
-	if (last >= length) {
+	if (last < 0 || last >= length) {
 	    last = length - 1;
 	}
 	if (last < first) {
@@ -798,7 +798,7 @@ Tcl_GetRange(
 	    TclNumUtfChars(stringPtr->numChars, objPtr->bytes, objPtr->length);
 	}
 	if (stringPtr->numChars == objPtr->length) {
-	    if (last >= stringPtr->numChars) {
+	    if (last < 0 || last >= stringPtr->numChars) {
 		last = stringPtr->numChars - 1;
 	    }
 	    if (last < first) {
@@ -819,7 +819,7 @@ Tcl_GetRange(
 	FillUnicodeRep(objPtr);
 	stringPtr = GET_STRING(objPtr);
     }
-    if (last >= stringPtr->numChars) {
+    if (last < 0 || last >= stringPtr->numChars) {
 	last = stringPtr->numChars - 1;
     }
     if (last < first) {
@@ -2116,7 +2116,11 @@ Tcl_AppendFormatToObj(
 	    if (gotPrecision) {
 		numChars = Tcl_GetCharLength(segment);
 		if (precision < numChars) {
-		    segment = Tcl_GetRange(segment, 0, precision - 1);
+		    if (precision < 1) {
+			TclNewObj(segment);
+		    } else {
+			segment = Tcl_GetRange(segment, 0, precision - 1);
+		    }
 		    numChars = precision;
 		    Tcl_IncrRefCount(segment);
 		    allocSegment = 1;
diff --git a/generic/tclTest.c b/generic/tclTest.c
index ed016fe..8d22edf 100644
--- a/generic/tclTest.c
+++ b/generic/tclTest.c
@@ -3918,7 +3918,7 @@ TestregexpObjCmd(
 	    if (ii == -1) {
 		TclRegExpRangeUniChar(regExpr, ii, &start, &end);
 		newPtr = Tcl_GetRange(objPtr, start, end);
-	    } else if (ii > info.nsubs) {
+	    } else if (ii > info.nsubs || info.matches[ii].end <= 0) {
 		newPtr = Tcl_NewObj();
 	    } else {
 		newPtr = Tcl_GetRange(objPtr, info.matches[ii].start,
-- 
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