1 files changed, 81 insertions, 63 deletions

diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index 93ed50b..151a899 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -5089,16 +5089,9 @@ TEBCresume(
 	    goto gotError;
 	}
 
-	/*
-	 * Select the list item based on the index. Negative operand means
-	 * end-based indexing.
-	 */
+	/* Decode end-offset index values. */
 
-	if (opnd < -1) {
-	    index = opnd+1 + objc;
-	} else {
-	    index = opnd;
-	}
+	index = TclIndexDecode(opnd, objc - 1);
 	pcAdjustment = 5;
 
     lindexFastPath:
@@ -5246,60 +5239,58 @@ TEBCresume(
 	}
 #endif
 
-	/*
-	 * Adjust the indices for end-based handling.
+	/* Decode index value operands. */
+
+	/* 
+	assert ( toIdx != TCL_INDEX_AFTER);
+	 *
+	 * Extra safety for legacy bytecodes:
 	 */
+	if (toIdx == TCL_INDEX_AFTER) {
+	    toIdx = TCL_INDEX_END;
+	}
 
-	if (fromIdx < -1) {
-	    fromIdx += 1+objc;
-	    if (fromIdx < -1) {
-		fromIdx = -1;
-	    }
-	} else if (fromIdx > objc) {
-	    fromIdx = objc;
+	if ((toIdx == TCL_INDEX_BEFORE) || (fromIdx == TCL_INDEX_AFTER)) {
+	    goto emptyList;
 	}
-	if (toIdx < -1) {
-	    toIdx += 1 + objc;
-	    if (toIdx < -1) {
-		toIdx = -1;
-	    }
-	} else if (toIdx > objc) {
-	    toIdx = objc;
+	toIdx = TclIndexDecode(toIdx, objc - 1);
+	if (toIdx < 0) {
+	    goto emptyList;
+	} else if (toIdx >= objc) {
+	    toIdx = objc - 1;
 	}
 
+	assert ( toIdx >= 0 && toIdx < objc);
 	/*
-	 * Check if we are referring to a valid, non-empty list range, and if
-	 * so, build the list of elements in that range.
+	assert ( fromIdx != TCL_INDEX_BEFORE );
+	 *
+	 * Extra safety for legacy bytecodes:
 	 */
+	if (fromIdx == TCL_INDEX_BEFORE) {
+	    fromIdx = TCL_INDEX_START;
+	}
 
-	if (fromIdx<=toIdx && fromIdx<objc && toIdx>=0) {
-	    if (fromIdx < 0) {
-		fromIdx = 0;
-	    }
-	    if (toIdx >= objc) {
-		toIdx = objc-1;
-	    }
-	    if (fromIdx == 0 && toIdx != objc-1 && !Tcl_IsShared(valuePtr)) {
-		/*
-		 * BEWARE! This is looking inside the implementation of the
-		 * list type.
-		 */
-
-		List *listPtr = valuePtr->internalRep.twoPtrValue.ptr1;
+	fromIdx = TclIndexDecode(fromIdx, objc - 1);
+	if (fromIdx < 0) {
+	    fromIdx = 0;
+	}
 
-		if (listPtr->refCount == 1) {
-		    for (index=toIdx+1; index<objc ; index++) {
-			TclDecrRefCount(objv[index]);
-		    }
-		    listPtr->elemCount = toIdx+1;
-		    listPtr->canonicalFlag = 1;
-		    TclInvalidateStringRep(valuePtr);
-		    TRACE_APPEND(("%.30s\n", O2S(valuePtr)));
-		    NEXT_INST_F(9, 0, 0);
+	if (fromIdx <= toIdx) {
+	    /* Construct the subsquence list */
+	    /* unshared optimization */
+	    if (Tcl_IsShared(valuePtr)) {
+		objResultPtr = Tcl_NewListObj(toIdx-fromIdx+1, objv+fromIdx);
+	    } else {
+		if (toIdx != objc - 1) {
+		    Tcl_ListObjReplace(NULL, valuePtr, toIdx + 1,
+			    objc - 1 - toIdx, 0, NULL);
 		}
+		Tcl_ListObjReplace(NULL, valuePtr, 0, fromIdx, 0, NULL);
+		TRACE_APPEND(("%.30s\n", O2S(valuePtr)));
+		NEXT_INST_F(9, 0, 0);
 	    }
-	    objResultPtr = Tcl_NewListObj(toIdx-fromIdx+1, objv+fromIdx);
 	} else {
+	emptyList:
 	    TclNewObj(objResultPtr);
 	}
 
@@ -5645,31 +5636,58 @@ TEBCresume(
 	length = Tcl_GetCharLength(valuePtr);
 	TRACE(("\"%.20s\" %d %d => ", O2S(valuePtr), fromIdx, toIdx));
 
+	/* Every range of an empty value is an empty value */
+	if (length == 0) {
+	    TRACE_APPEND(("\n"));
+	    NEXT_INST_F(9, 0, 0);
+	}
+
+	/* Decode index operands. */
+
 	/*
-	 * Adjust indices for end-based indexing.
+	assert ( toIdx != TCL_INDEX_BEFORE );
+	assert ( toIdx != TCL_INDEX_AFTER);
+	 *
+	 * Extra safety for legacy bytecodes:
 	 */
-
-	if (fromIdx < -1) {
-	    fromIdx += 1 + length;
-	    if (fromIdx < 0) {
-		fromIdx = 0;
-	    }
-	} else if (fromIdx >= length) {
-	    fromIdx = length;
+	if (toIdx == TCL_INDEX_BEFORE) {
+	    goto emptyRange;
 	}
-	if (toIdx < -1) {
-	    toIdx += 1 + length;
+	if (toIdx == TCL_INDEX_AFTER) {
+	    toIdx = TCL_INDEX_END;
+	}
+
+	toIdx = TclIndexDecode(toIdx, length - 1);
+	if (toIdx < 0) {
+	    goto emptyRange;
 	} else if (toIdx >= length) {
 	    toIdx = length - 1;
 	}
 
+	assert ( toIdx >= 0 && toIdx < length );
+
 	/*
-	 * Check if we can do a sane substring.
+	assert ( fromIdx != TCL_INDEX_BEFORE );
+	assert ( fromIdx != TCL_INDEX_AFTER);
+	 *
+	 * Extra safety for legacy bytecodes:
 	 */
+	if (fromIdx == TCL_INDEX_BEFORE) {
+	    fromIdx = TCL_INDEX_START;
+	}
+	if (fromIdx == TCL_INDEX_AFTER) {
+	    goto emptyRange;
+	}
+
+	fromIdx = TclIndexDecode(fromIdx, length - 1);
+	if (fromIdx < 0) {
+	    fromIdx = 0;
+	}
 
 	if (fromIdx <= toIdx) {
 	    objResultPtr = Tcl_GetRange(valuePtr, fromIdx, toIdx);
 	} else {
+	emptyRange:
 	    TclNewObj(objResultPtr);
 	}
 	TRACE_APPEND(("%.30s\n", O2S(objResultPtr)));