* generic/tclTest.c: Added two new functions to allocate memory

	from the execution stack (TclStackAlloc, TclStackFree). Added
	functions TclPushStackFrame and TclPopStackFrame that do the work
	of Tcl_PushCallFrame and Tcl_PopCallFrame, but using frames
	allocated in the execution stack - i.e., heap instead of
	C-stack. The core uses these two new functions exclusively; the
	old ones remain for backwards compat, as at least two popular
	extensions (itcl, xotcl) are known to use them.

1 files changed, 82 insertions, 1 deletions

diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index 99cf90a..afbb4aa 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -11,7 +11,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclExecute.c,v 1.167 2004/11/12 19:16:50 dgp Exp $
+ * RCS: @(#) $Id: tclExecute.c,v 1.168 2004/12/15 20:44:36 msofer Exp $
  */
 
 #include "tclInt.h"
@@ -659,6 +659,87 @@ GrowEvaluationStack(eePtr)
 /*
  *--------------------------------------------------------------
  *
+ * TclStackAlloc --
+ *
+ *	Allocate memory from the execution stack; it has to be returned later
+ *	with a call to TclStackFree
+ *
+ * Results:
+ *	A pointer to the first byte allocated, or panics if the allocation did 
+ *      not succeed.
+ *
+ * Side effects:
+ *	The execution stack may be grown.
+ *
+ *--------------------------------------------------------------
+ */
+
+char *
+TclStackAlloc(interp, numBytes)
+    Tcl_Interp *interp;
+    int numBytes;
+{
+    Interp *iPtr = (Interp *) interp;
+    ExecEnv *eePtr = iPtr->execEnvPtr;
+    int numWords;
+    Tcl_Obj **tosPtr = eePtr->tosPtr;
+    char **stackRefCountPtr;
+    
+    /*
+     * Add two words to store
+     *   - a pointer to the used execution stack
+     *   - the number of words reserved
+     * These will be used later by TclStackFree. 
+     */
+    
+    numWords = (numBytes + 3*sizeof(void *) - 1)/sizeof(void *);
+
+    while ((tosPtr + numWords) > eePtr->endPtr) {
+	GrowEvaluationStack(eePtr);
+	tosPtr = eePtr->tosPtr;
+    }
+
+    /*
+     * Increase the stack's reference count, to make sure it is not freed
+     * prematurely. 
+     */ 
+
+    stackRefCountPtr = (char **) (eePtr->stackPtr-1);
+    ++*stackRefCountPtr;
+    
+    /*
+     * Reserve the space in the exec stack, and store the data for freeing.
+     */
+    
+    eePtr->tosPtr += numWords;
+    *(eePtr->tosPtr-1) = (Tcl_Obj *) stackRefCountPtr;
+    *(eePtr->tosPtr)   = (Tcl_Obj *) numWords;
+
+    return (char *) (tosPtr+1);    
+}
+
+void
+TclStackFree(interp) 
+    Tcl_Interp *interp;
+{
+    Interp *iPtr = (Interp *) interp;
+    ExecEnv *eePtr = iPtr->execEnvPtr;
+    char **stackRefCountPtr;
+
+    
+    stackRefCountPtr = (char **) *(eePtr->tosPtr-1);
+    eePtr->tosPtr -= (int) *(eePtr->tosPtr);
+    
+    --*stackRefCountPtr;
+    if (*stackRefCountPtr == (char *) 0) {
+	ckfree((VOID *) stackRefCountPtr);
+    }	    
+}
+
+
+/*
+ *--------------------------------------------------------------
+ *
  * Tcl_ExprObj --
  *
  *	Evaluate an expression in a Tcl_Obj.