From ec332750d28a86537a3fc721decc3bb74d850dc9 Mon Sep 17 00:00:00 2001
From: dgp <dgp@users.sourceforge.net>
Date: Thu, 27 Oct 2016 19:39:49 +0000
Subject: Start bringing all `string cat` operations into one place so it can
 be coded correctly one time instead of badly multiple times.

---
 generic/tclCmdMZ.c     | 17 ++++++++---------
 generic/tclInt.h       |  2 ++
 generic/tclStringObj.c | 40 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 9 deletions(-)

diff --git a/generic/tclCmdMZ.c b/generic/tclCmdMZ.c
index 591e31c..1a08674 100644
--- a/generic/tclCmdMZ.c
+++ b/generic/tclCmdMZ.c
@@ -2855,7 +2855,7 @@ StringCatCmd(
     int objc,			/* Number of arguments. */
     Tcl_Obj *const objv[])	/* Argument objects. */
 {
-    int i;
+    int code;
     Tcl_Obj *objResultPtr;
 
     if (objc < 2) {
@@ -2872,16 +2872,15 @@ StringCatCmd(
 	Tcl_SetObjResult(interp, objv[1]);
 	return TCL_OK;
     }
-    objResultPtr = objv[1];
-    if (Tcl_IsShared(objResultPtr)) {
-	objResultPtr = Tcl_DuplicateObj(objResultPtr);
-    }
-    for(i = 2;i < objc;i++) {
-	Tcl_AppendObjToObj(objResultPtr, objv[i]);
+
+    code = TclStringCatObjv(interp, objc-1, objv+1, &objResultPtr);
+
+    if (code == TCL_OK) {
+	Tcl_SetObjResult(interp, objResultPtr);
+	return TCL_OK;
     }
-    Tcl_SetObjResult(interp, objResultPtr);
 
-    return TCL_OK;
+    return code;
 }
 
 /*
diff --git a/generic/tclInt.h b/generic/tclInt.h
index da1b5c5..36c1a81 100644
--- a/generic/tclInt.h
+++ b/generic/tclInt.h
@@ -3135,6 +3135,8 @@ MODULE_SCOPE void	TclSpellFix(Tcl_Interp *interp,
 			    Tcl_Obj *bad, Tcl_Obj *fix);
 MODULE_SCOPE void *	TclStackRealloc(Tcl_Interp *interp, void *ptr,
 			    int numBytes);
+MODULE_SCOPE int	TclStringCatObjv(Tcl_Interp *interp, int objc,
+			    Tcl_Obj *const objv[], Tcl_Obj **objPtrPtr);
 MODULE_SCOPE int	TclStringMatch(const char *str, int strLen,
 			    const char *pattern, int ptnLen, int flags);
 MODULE_SCOPE int	TclStringMatchObj(Tcl_Obj *stringObj,
diff --git a/generic/tclStringObj.c b/generic/tclStringObj.c
index 2930fa1..1828d20 100644
--- a/generic/tclStringObj.c
+++ b/generic/tclStringObj.c
@@ -2598,6 +2598,46 @@ TclGetStringStorage(
     *sizePtr = stringPtr->allocated;
     return objPtr->bytes;
 }
+
+/*
+ *---------------------------------------------------------------------------
+ *
+ * TclStringCatObjv --
+ *
+ *	Performs the [string cat] function.
+ *
+ * Results:
+ * 	A standard Tcl result.
+ *
+ * Side effects:
+ * 	Writes to *objPtrPtr the address of Tcl_Obj that is concatenation
+ * 	of all objc values in objv.
+ *
+ *---------------------------------------------------------------------------
+ */
+
+int
+TclStringCatObjv(
+    Tcl_Interp *interp,
+    int objc,
+    Tcl_Obj * const objv[],
+    Tcl_Obj **objPtrPtr)
+{
+    Tcl_Obj *objResultPtr;
+
+    /* assert (objc >= 2) */
+
+    objResultPtr = *objv++; objc--;
+    if (Tcl_IsShared(objResultPtr)) {
+	objResultPtr = Tcl_DuplicateObj(objResultPtr);
+    }
+    while (objc--) {
+	Tcl_AppendObjToObj(objResultPtr, *objv++);
+    }
+    *objPtrPtr = objResultPtr;
+    return TCL_OK;
+}
+
 /*
  *---------------------------------------------------------------------------
  *
-- 
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