Looks like TCL_INIT_CUSTOM (previously known as TCL_INIT_STUFF) is not a bad idea at all,

provided it has a Tcl_Interp* argument as well, so it can initialize the stub table.
A typedef for the function is not necessary, as a variable-argument function doesn't do any type checking. It's for the experienced developer anyway.

3 files changed, 16 insertions, 12 deletions

diff --git a/doc/InitSubSyst.3 b/doc/InitSubSyst.3
index 4a3dc64..db3951e 100644
--- a/doc/InitSubSyst.3
+++ b/doc/InitSubSyst.3
@@ -19,7 +19,7 @@ Tcl_Interp *
 .AS int flags
 .AP int flags in
 Any combination of flags which might modify the initialization sequence.
-At this moment, only 0, \fBTCL_INIT_PANIC\fR and \fBTCL_INIT_STUFF\fR
+At this moment, only 0, \fBTCL_INIT_PANIC\fR and \fBTCL_INIT_CUSTOM\fR
 (or a combination) are supported.
 The value 0 can be used if Tcl is used as utility library only.
 .BE
@@ -75,13 +75,15 @@ could call \fBTcl_SetPanicProc\fR immediately after \fBTcl_InitSubsystems\fR,
 but then panics which could be produced by the initialization
 itself still use the default panic procedure. 
 .PP
-If you supply the flag \fBTCL_INIT_STUFF\fR to \fBTcl_InitSubsystems\fR,
+If you supply the flag \fBTCL_INIT_CUSTOM\fR to \fBTcl_InitSubsystems\fR,
 the function expects two additional arguments: ClientData and a
-custom proc with has ClientData as its only argument. The given
-function will be executed just before the encodings are initialized.
+custom proc. The proc will be supplied two arguments, the (pseudo)
+Tcl interpreter and ClientData. The given function will be executed
+just before the encodings are initialized.
 .PP
-The interpreter returned by Tcl_InitSubsystems(0) cannot be passed to
-any other function than Tcl_InitStubs(). Tcl functions with an "interp"
-argument can only be called if the function supports passing NULL.
+The interpreter returned by Tcl_InitSubsystems(0) or passed to the
+TCL_INIT_CUSTOM function cannot be passed to any other function than
+Tcl_InitStubs(). Tcl functions with an "interp" argument can only
+be called if the function supports passing NULL.
 .SH KEYWORDS
 binary, executable file
diff --git a/generic/tcl.h b/generic/tcl.h
index 9325bf2..522171e 100644
--- a/generic/tcl.h
+++ b/generic/tcl.h
@@ -2412,7 +2412,7 @@ const char *		TclTomMathInitializeStubs(Tcl_Interp *interp,
 /* Tcl_InitSubsystems, see TIP #414 */
 
 #define TCL_INIT_PANIC (1) /* Set Panic proc */
-#define TCL_INIT_STUFF (2) /* Do any stuff before initializing the encoding */
+#define TCL_INIT_CUSTOM (2) /* Do any stuff before initializing the encoding */
 
 EXTERN Tcl_Interp *Tcl_InitSubsystems(int flags, ...);
 
diff --git a/generic/tclEncoding.c b/generic/tclEncoding.c
index 753222f..9905eaa 100644
--- a/generic/tclEncoding.c
+++ b/generic/tclEncoding.c
@@ -1446,22 +1446,24 @@ Tcl_Interp *
 Tcl_InitSubsystems(int flags, ...)
 {
     va_list argList;
+    Tcl_Interp *interp = (Tcl_Interp *) &dummyInterp;
 
     va_start(argList, flags);
     if (flags & TCL_INIT_PANIC) {
 	Tcl_SetPanicProc(va_arg(argList, Tcl_PanicProc *));
     }
     TclInitSubsystems();
-    if (flags & TCL_INIT_STUFF) {
+    if (flags & TCL_INIT_CUSTOM) {
 	ClientData clientData = va_arg(argList, ClientData);
-	void (*fn)() = va_arg(argList, void (*)(ClientData));
-	fn(clientData);
+	void (*fn)(Tcl_Interp *, ClientData) = va_arg(argList,
+		void (*)(Tcl_Interp *, ClientData));
+	fn(interp, clientData);
     }
     va_end(argList);
 
     TclpSetInitialEncodings();
     TclpFindExecutable(NULL);
-    return (Tcl_Interp *) &dummyInterp;
+    return interp;
 }
 
 void