change stub library to detect - and generate a nice error-message -

when a shared library compiled for Tcl 9.x is attempted to be
loaded in Tcl 8.x. Change MAGIC value in stub tables for 64-bit
builds (those surely will be incomatible!)

2 files changed, 20 insertions, 11 deletions

diff --git a/generic/tcl.h b/generic/tcl.h
index 9ea2e90..c18b251 100644
--- a/generic/tcl.h
+++ b/generic/tcl.h
@@ -136,6 +136,7 @@ extern "C" {
  */
 
 #include <stdio.h>
+#include <stddef.h>
 
 /*
  *----------------------------------------------------------------------------
@@ -2274,12 +2275,9 @@ typedef int (Tcl_NRPostProc) (ClientData data[], Tcl_Interp *interp,
  *----------------------------------------------------------------------------
  * The following constant is used to test for older versions of Tcl in the
  * stubs tables.
- *
- * Jan Nijtman's plus patch uses 0xFCA1BACF, so we need to pick a different
- * value since the stubs tables don't match.
  */
 
-#define TCL_STUB_MAGIC		((int) 0xFCA3BACF)
+#define TCL_STUB_MAGIC		((int) 0xFCA3BACB + sizeof(size_t))
 
 /*
  * The following function is required to be defined in all stubs aware
diff --git a/generic/tclStubLib.c b/generic/tclStubLib.c
index f569820..bd8f6e7 100644
--- a/generic/tclStubLib.c
+++ b/generic/tclStubLib.c
@@ -38,14 +38,25 @@ HasStubSupport(
 {
     Interp *iPtr = (Interp *) interp;
 
-    if (iPtr->stubTable && (iPtr->stubTable->magic == TCL_STUB_MAGIC)) {
-	return iPtr->stubTable;
+    if (!iPtr->stubTable) {
+	/* No stub table at all? Nothing we can do. */
+	return NULL;
     }
-
-    iPtr->result =
-	    (char *)"This interpreter does not support stubs-enabled extensions.";
-    iPtr->freeProc = TCL_STATIC;
-    return NULL;
+    if (iPtr->stubTable->magic != TCL_STUB_MAGIC) {
+	/*
+	 * The iPtr->stubTable entry from Tcl_Interp and the
+	 * Tcl_NewStringObj() and Tcl_SetObjResult() entries
+	 * in the stub table cannot change in Tcl 9 compared
+	 * to Tcl 8.x. Otherwise the lines below won't work.
+	 * TODO: add a test case for that.
+	 */
+	iPtr->stubTable->tcl_SetObjResult(interp,
+		iPtr->stubTable->tcl_NewStringObj(
+			"This extension is compiled for Tcl 9.x",
+			TCL_NOSIZE));
+	return NULL;
+    }
+    return iPtr->stubTable;
 }
 
 /*