When appropriate, implement [join] with the common [string cat] engine.

1 files changed, 36 insertions, 15 deletions

diff --git a/generic/tclCmdIL.c b/generic/tclCmdIL.c
index bb3c9b7..09adc8d 100644
--- a/generic/tclCmdIL.c
+++ b/generic/tclCmdIL.c
@@ -2155,8 +2155,8 @@ Tcl_JoinObjCmd(
     int objc,			/* Number of arguments. */
     Tcl_Obj *const objv[])	/* The argument objects. */
 {
-    int listLen, i;
-    Tcl_Obj *resObjPtr, *joinObjPtr, **elemPtrs;
+    int listLen;
+    Tcl_Obj *resObjPtr = NULL, *joinObjPtr, **elemPtrs;
 
     if ((objc < 2) || (objc > 3)) {
 	Tcl_WrongNumArgs(interp, 1, objv, "list ?joinString?");
@@ -2173,27 +2173,48 @@ Tcl_JoinObjCmd(
 	return TCL_ERROR;
     }
 
+    if (listLen == 0) {
+	/* No elements to join; default empty result is correct. */
+	return TCL_OK;
+    }
+    if (listLen == 1) {
+	/* One element; return it */
+	Tcl_SetObjResult(interp, elemPtrs[0]);
+	return TCL_OK;
+    }
+
     joinObjPtr = (objc == 2) ? Tcl_NewStringObj(" ", 1) : objv[2];
     Tcl_IncrRefCount(joinObjPtr);
 
-    resObjPtr = Tcl_NewObj();
-    for (i = 0;  i < listLen;  i++) {
-	if (i > 0) {
+    if (Tcl_GetCharLength(joinObjPtr) == 0) {
+	Tcl_IncrRefCount(elemPtrs[0]);
+	TclStringCatObjv(interp, listLen, elemPtrs, &resObjPtr);
+	Tcl_DecrRefCount(elemPtrs[0]);
+    } else {
+	int i;
 
-	    /*
-	     * NOTE: This code is relying on Tcl_AppendObjToObj() **NOT**
-	     * to shimmer joinObjPtr.  If it did, then the case where
-	     * objv[1] and objv[2] are the same value would not be safe.
-	     * Accessing elemPtrs would crash.
-	     */
+	resObjPtr = Tcl_NewObj();
+	for (i = 0;  i < listLen;  i++) {
+	    if (i > 0) {
 
-	    Tcl_AppendObjToObj(resObjPtr, joinObjPtr);
+		/*
+		 * NOTE: This code is relying on Tcl_AppendObjToObj() **NOT**
+		 * to shimmer joinObjPtr.  If it did, then the case where
+		 * objv[1] and objv[2] are the same value would not be safe.
+		 * Accessing elemPtrs would crash.
+		 */
+
+		Tcl_AppendObjToObj(resObjPtr, joinObjPtr);
+	    }
+	    Tcl_AppendObjToObj(resObjPtr, elemPtrs[i]);
 	}
-	Tcl_AppendObjToObj(resObjPtr, elemPtrs[i]);
     }
     Tcl_DecrRefCount(joinObjPtr);
-    Tcl_SetObjResult(interp, resObjPtr);
-    return TCL_OK;
+    if (resObjPtr) {
+	Tcl_SetObjResult(interp, resObjPtr);
+	return TCL_OK;
+    }
+    return TCL_ERROR;
 }
 
 /*