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.

2 files changed, 7 insertions, 5 deletions

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