tcl/tcl-refchan-mode-needed.patch

--- doc/refchan.n.orig
+++ doc/refchan.n
@@ -53,8 +53,8 @@ here, then the \fBfinalize\fR subcommand
 .PP
 The \fImode\fR argument tells the handler whether the channel was
 opened for reading, writing, or both. It is a list containing any of
-the strings \fBread\fR or \fBwrite\fR. The list will always
-contain at least one element.
+the strings \fBread\fR or \fBwrite\fR. The list may be empty, but
+will usually contain at least one element. 
 .PP
 The subcommand must throw an error if the chosen mode is not
 supported by the \fIcmdPrefix\fR.
--- generic/tclIORChan.c.orig
+++ generic/tclIORChan.c
@@ -425,7 +425,7 @@ static void		UnmarshallErrorResult(Tcl_I
  */
 
 static int		EncodeEventMask(Tcl_Interp *interp,
-			    const char *objName, Tcl_Obj *obj, int *mask);
+			    const char *objName, Tcl_Obj *obj, int *mask, int needed);
 static Tcl_Obj *	DecodeEventMask(int mask);
 static ReflectedChannel * NewReflectedChannel(Tcl_Interp *interp,
 			    Tcl_Obj *cmdpfxObj, int mode, Tcl_Obj *handleObj);
@@ -532,11 +532,11 @@ TclChanCreateObjCmd(
 
     /*
      * First argument is a list of modes. Allowed entries are "read", "write".
-     * Expect at least one list element. Abbreviations are ok.
+     * Empty list is uncommon, but allowed. Abbreviations are ok.
      */
 
     modeObj = objv[MODE];
-    if (EncodeEventMask(interp, "mode", objv[MODE], &mode) != TCL_OK) {
+    if (EncodeEventMask(interp, "mode", objv[MODE], &mode, 0) != TCL_OK) {
 	return TCL_ERROR;
     }
 
@@ -902,7 +902,7 @@ TclChanPostEventObjCmd(
      * "write". Expect at least one list element. Abbreviations are ok.
      */
 
-    if (EncodeEventMask(interp, "event", objv[EVENT], &events) != TCL_OK) {
+    if (EncodeEventMask(interp, "event", objv[EVENT], &events, 1) != TCL_OK) {
 	return TCL_ERROR;
     }
 
@@ -2007,8 +2007,9 @@ ReflectGetOption(
  * EncodeEventMask --
  *
  *	This function takes a list of event items and constructs the
- *	equivalent internal bitmask. The list must contain at least one
- *	element. Elements are "read", "write", or any unique abbreviation of
+ *	equivalent internal bitmask. The list may be empty if the last
+ *	argument is 0, otherwise it must contain at least one element.
+ *	Elements are "read", "write", or any unique abbreviation of
  *	them. Note that the bitmask is not changed if problems are
  *	encountered.
  *
@@ -2028,7 +2029,8 @@ EncodeEventMask(
     Tcl_Interp *interp,
     const char *objName,
     Tcl_Obj *obj,
-    int *mask)
+    int *mask,
+    int needed)
 {
     int events;			/* Mask of events to post */
     int listc;			/* #elements in eventspec list */
@@ -2040,7 +2042,7 @@ EncodeEventMask(
 	return TCL_ERROR;
     }
 
-    if (listc < 1) {
+    if (needed && listc < 1) {
 	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
                 "bad %s list: is empty", objName));
 	return TCL_ERROR;
--- tests/ioCmd.test.orig
+++ tests/ioCmd.test
@@ -670,12 +670,12 @@ test iocmd-21.1 {chan create, wrong#args
     catch {chan create a b c} msg
     set msg
 } {wrong # args: should be "chan create mode cmdprefix"}
-test iocmd-21.2 {chan create, invalid r/w mode, empty} {
-    proc foo {} {}
-    catch {chan create {} foo} msg
+test iocmd-21.2 {chan create, r/w mode empty} {
+    proc foo {cmd args} { return "initialize finalize watch" }
+    set chan [chan create {} foo]
+    close $chan
     rename foo {}
-    set msg
-} {bad mode list: is empty}
+} {}
 test iocmd-21.3 {chan create, invalid r/w mode, bad string} {
     proc foo {} {}
     catch {chan create {c} foo} msg