Index: generic/tclBasic.c
===================================================================
RCS file: /cvsroot/tcl/tcl/generic/tclBasic.c,v
retrieving revision 1.404
diff -u -r1.404 tclBasic.c
--- generic/tclBasic.c	11 Sep 2009 20:13:27 -0000	1.404
+++ generic/tclBasic.c	20 Oct 2009 16:07:56 -0000
@@ -530,6 +530,10 @@
     iPtr->errorInfo = NULL;
     TclNewLiteralStringObj(iPtr->eiVar, "::errorInfo");
     Tcl_IncrRefCount(iPtr->eiVar);
+    iPtr->errorStack = Tcl_NewListObj(0, NULL);
+    Tcl_IncrRefCount(iPtr->errorStack);
+    iPtr->useErrorStack=0;
+    iPtr->resetErrorStack = 1;
     iPtr->errorCode = NULL;
     TclNewLiteralStringObj(iPtr->ecVar, "::errorCode");
     Tcl_IncrRefCount(iPtr->ecVar);
@@ -792,6 +796,14 @@
 	    Tcl_RepresentationCmd, NULL, NULL);
 
     /*
+     * TIP 348
+     */
+
+    Tcl_LinkVar(interp, "::tcl::useErrorStack",
+		(char *) &iPtr->useErrorStack,
+		TCL_LINK_INT);
+
+    /*
      * Create the 'tailcall' command
      */
 
@@ -1470,6 +1482,7 @@
 	Tcl_DecrRefCount(iPtr->errorInfo);
 	iPtr->errorInfo = NULL;
     }
+    Tcl_DecrRefCount(iPtr->errorStack);
     if (iPtr->returnOpts) {
 	Tcl_DecrRefCount(iPtr->returnOpts);
     }
@@ -8821,5 +8834,7 @@
  * mode: c
  * c-basic-offset: 4
  * fill-column: 78
+ * tab-width: 8
+ * indent-tabs-mode: nil
  * End:
  */
Index: generic/tclCmdIL.c
===================================================================
RCS file: /cvsroot/tcl/tcl/generic/tclCmdIL.c,v
retrieving revision 1.171
diff -u -r1.171 tclCmdIL.c
--- generic/tclCmdIL.c	20 Aug 2009 10:56:55 -0000	1.171
+++ generic/tclCmdIL.c	20 Oct 2009 16:07:56 -0000
@@ -118,6 +118,9 @@
 			    int objc, Tcl_Obj *const objv[]);
 static int		InfoDefaultCmd(ClientData dummy, Tcl_Interp *interp,
 			    int objc, Tcl_Obj *const objv[]);
+/* TIP #348 - New 'info' subcommand 'errorstack' */
+static int		InfoErrorStackCmd(ClientData dummy, Tcl_Interp *interp,
+			    int objc, Tcl_Obj *const objv[]);
 /* TIP #280 - New 'info' subcommand 'frame' */
 static int		InfoFrameCmd(ClientData dummy, Tcl_Interp *interp,
 			    int objc, Tcl_Obj *const objv[]);
@@ -164,6 +167,7 @@
     {"complete",	   InfoCompleteCmd,	    NULL},
     {"coroutine",	   TclInfoCoroutineCmd,     NULL},
     {"default",		   InfoDefaultCmd,	    NULL},
+    {"errorstack",	   InfoErrorStackCmd,	    NULL},
     {"exists",		   TclInfoExistsCmd,	    TclCompileInfoExistsCmd},
     {"frame",		   InfoFrameCmd,	    NULL},
     {"functions",	   InfoFunctionsCmd,	    NULL},
@@ -1017,6 +1021,55 @@
 /*
  *----------------------------------------------------------------------
  *
+ * InfoErrorStackCmd --
+ *
+ *	Called to implement the "info errorstack" command that returns information
+ *	about the last error's call stack. Handles the following syntax:
+ *
+ *	    info errorstack ?interp?
+ *
+ * Results:
+ *	Returns TCL_OK if successful and TCL_ERROR if there is an error.
+ *
+ * Side effects:
+ *	Returns a result in the interpreter's result object. If there is an
+ *	error, the result is an error message.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+InfoErrorStackCmd(
+    ClientData dummy,		/* Not used. */
+    Tcl_Interp *interp,		/* Current interpreter. */
+    int objc,			/* Number of arguments. */
+    Tcl_Obj *const objv[])	/* Argument objects. */
+{
+    Tcl_Interp *target;
+    Interp *iPtr;
+
+    if ((objc != 1) && (objc != 2)) {
+	Tcl_WrongNumArgs(interp, 1, objv, "?interp?");
+	return TCL_ERROR;
+    }
+    
+    target = interp;
+    if (objc == 2) {
+        target = Tcl_GetSlave(interp, Tcl_GetString(objv[1]));
+        if (target == NULL) {
+            return TCL_ERROR;
+        }
+    }
+
+    iPtr = (Interp *) target;
+    Tcl_SetObjResult(interp, iPtr->errorStack);
+    
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
  * TclInfoExistsCmd --
  *
  *	Called to implement the "info exists" command that determines whether
@@ -4388,5 +4441,7 @@
  * mode: c
  * c-basic-offset: 4
  * fill-column: 78
+ * tab-width: 8
+ * indent-tabs-mode: nil
  * End:
  */
Index: generic/tclInt.h
===================================================================
RCS file: /cvsroot/tcl/tcl/generic/tclInt.h,v
retrieving revision 1.445
diff -u -r1.445 tclInt.h
--- generic/tclInt.h	30 Sep 2009 03:11:26 -0000	1.445
+++ generic/tclInt.h	20 Oct 2009 16:07:57 -0000
@@ -1895,6 +1895,9 @@
     Tcl_Obj *eiVar;		/* cached ref to ::errorInfo variable. */
     Tcl_Obj *errorCode;		/* errorCode value (now as a Tcl_Obj). */
     Tcl_Obj *ecVar;		/* cached ref to ::errorInfo variable. */
+    Tcl_Obj *errorStack;	/* ::tcl::errorStack value (as a Tcl_Obj). */
+    int resetErrorStack;        /* controls cleaning up of ::errorStack */
+    int useErrorStack;          /* linked var gating ::errorStack overhead */
     int returnLevel;		/* [return -level] parameter. */
 
     /*
Index: generic/tclNamesp.c
===================================================================
RCS file: /cvsroot/tcl/tcl/generic/tclNamesp.c,v
retrieving revision 1.193
diff -u -r1.193 tclNamesp.c
--- generic/tclNamesp.c	30 Sep 2009 03:11:26 -0000	1.193
+++ generic/tclNamesp.c	20 Oct 2009 16:07:59 -0000
@@ -7633,6 +7633,41 @@
 		    TCL_GLOBAL_ONLY);
 	}
     }
+
+    /*
+     * TIP #348
+     */
+
+    if (iPtr->useErrorStack) {
+	int len;
+        
+	if (Tcl_IsShared(iPtr->errorStack)) {
+	    Tcl_Obj *newObj;
+            
+	    newObj = Tcl_DuplicateObj(iPtr->errorStack);
+	    Tcl_DecrRefCount(iPtr->errorStack);
+	    Tcl_IncrRefCount(newObj);
+	    iPtr->errorStack = newObj;
+	}
+	Tcl_ListObjLength(interp, iPtr->errorStack, &len);
+	if (iPtr->resetErrorStack) {
+	    iPtr->resetErrorStack = 0;
+	    /* reset while keeping the list intrep as much as possible */
+	    Tcl_ListObjReplace(interp, iPtr->errorStack, 0, len, 0, NULL);
+	    len=0;
+	} 
+	if (iPtr->varFramePtr != iPtr->rootFramePtr) {
+	    Tcl_Obj *listPtr;
+	    int result;
+            
+	    listPtr=Tcl_NewListObj(iPtr->varFramePtr->objc,
+				   iPtr->varFramePtr->objv);
+	    result = Tcl_ListObjReplace(interp, iPtr->errorStack, len, 1, 1, &listPtr);
+	    if (result != TCL_OK) {
+		Tcl_DecrRefCount(listPtr);
+	    }
+	}
+    }
 }
 
 /*
@@ -7640,5 +7675,7 @@
  * mode: c
  * c-basic-offset: 4
  * fill-column: 78
+ * tab-width: 8
+ * indent-tabs-mode: nil
  * End:
  */
Index: generic/tclResult.c
===================================================================
RCS file: /cvsroot/tcl/tcl/generic/tclResult.c,v
retrieving revision 1.54
diff -u -r1.54 tclResult.c
--- generic/tclResult.c	17 Dec 2008 16:47:38 -0000	1.54
+++ generic/tclResult.c	20 Oct 2009 16:07:59 -0000
@@ -19,7 +19,7 @@
 
 enum returnKeys {
     KEY_CODE,	KEY_ERRORCODE,	KEY_ERRORINFO,	KEY_ERRORLINE,
-    KEY_LEVEL,	KEY_OPTIONS,	KEY_LAST
+    KEY_LEVEL,	KEY_OPTIONS,	KEY_ERRORSTACK,	KEY_LAST
 };
 
 /*
@@ -922,6 +922,7 @@
 	Tcl_DecrRefCount(iPtr->errorInfo);
 	iPtr->errorInfo = NULL;
     }
+    iPtr->resetErrorStack = 1;
     iPtr->returnLevel = 1;
     iPtr->returnCode = TCL_OK;
     if (iPtr->returnOpts) {
@@ -1158,6 +1159,7 @@
 	TclNewLiteralStringObj(keys[KEY_ERRORCODE], "-errorcode");
 	TclNewLiteralStringObj(keys[KEY_ERRORINFO], "-errorinfo");
 	TclNewLiteralStringObj(keys[KEY_ERRORLINE], "-errorline");
+	TclNewLiteralStringObj(keys[KEY_ERRORSTACK],"-errorstack");
 	TclNewLiteralStringObj(keys[KEY_LEVEL],	    "-level");
 	TclNewLiteralStringObj(keys[KEY_OPTIONS],   "-options");
 
@@ -1503,6 +1505,9 @@
 	Tcl_DictObjPut(NULL, options, keys[KEY_ERRORLINE],
 		Tcl_NewIntObj(iPtr->errorLine));
     }
+    if (iPtr->useErrorStack > 1) {
+	Tcl_DictObjPut(NULL, options, keys[KEY_ERRORSTACK], iPtr->errorStack);
+    }
     return options;
 }
 
@@ -1624,5 +1629,7 @@
  * mode: c
  * c-basic-offset: 4
  * fill-column: 78
+ * tab-width: 8
+ * indent-tabs-mode: nil
  * End:
  */
Index: tests/error.test
===================================================================
RCS file: /cvsroot/tcl/tcl/tests/error.test,v
retrieving revision 1.22
diff -u -r1.22 error.test
--- tests/error.test	28 Sep 2009 18:02:20 -0000	1.22
+++ tests/error.test	20 Oct 2009 16:08:00 -0000
@@ -152,6 +152,33 @@
     set ::errorCode bogus
     list [catch {error msg1 msg2 {}} msg] $msg $::errorInfo $::errorCode
 } {1 msg1 msg2 {}}
+test error-4.6 {errorStack disabled by default} {
+	proc f x {g $x$x}
+	proc g x {error G:$x}
+	catch {f 12}
+    info errorstack
+} {}
+test error-4.7 {errorStack disabled by useErrorStack} {
+	set ::tcl::useErrorStack 0
+	proc f x {g $x$x}
+	proc g x {error G:$x}
+	catch {f 12}
+	info errorstack
+} {}
+test error-4.8 {errorStack enabled by useErrorStack} -body {
+	set ::tcl::useErrorStack 1
+	proc f x {g $x$x}
+	proc g x {error G:$x}
+	catch {f 12}
+    info errorstack
+} -match glob -result {{g 1212} {f 12} {namespace eval *}}
+test error-4.9 {options dict -errorstack key enabled by useErrorStack} -body {
+	set ::tcl::useErrorStack 2
+	proc f x {g $x$x}
+	proc g x {error G:$x}
+	catch {f 12} m d
+    dict get $d -errorstack
+} -match glob -result {{g 1212} {f 12} {namespace eval *}}
 
 # Errors in error command itself
 
@@ -207,6 +234,16 @@
     catch foo
     list $::errorCode
 } {NONE}
+test error-6.10 {catch must reset errorStack} -body {
+	set ::tcl::useErrorStack 1
+	proc f x {g $x$x}
+	proc g x {error G:$x}
+	catch {f 12}
+	set e1 [info errorstack]
+	catch {f 13}
+	set e2 [info errorstack]
+	list $e1 $e2
+} -match glob -result {{{g 1212} {f 12} {namespace eval *}} {{g 1313} {f 13} {namespace eval *}}}
 
 test error-7.1 {Bug 1397843} -body {
     variable cmds
