* win/tclWinInt.h:

* win/tclWin32Dll.c:
* unix/tclUnixInit.c: Added TclpCheckStackSpace.

2 files changed, 45 insertions, 2 deletions

diff --git a/win/tclWin32Dll.c b/win/tclWin32Dll.c
index 9de0589..c3de691 100644
--- a/win/tclWin32Dll.c
+++ b/win/tclWin32Dll.c
@@ -9,7 +9,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclWin32Dll.c,v 1.4 1998/09/14 18:40:19 stanton Exp $
+ * RCS: @(#) $Id: tclWin32Dll.c,v 1.4.4.1 1999/03/04 00:59:04 stanton Exp $
  */
 
 #include "tclWinInt.h"
@@ -378,6 +378,41 @@ TclWinGetTclInstance()
 /*
  *----------------------------------------------------------------------
  *
+ * TclpCheckStackSpace --
+ *
+ *	Detect if we are about to blow the stack.  Called before an 
+ *	evaluation can happen when nesting depth is checked.
+ *
+ * Results:
+ *	1 if there is enough stack space to continue; 0 if not.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+int
+TclpCheckStackSpace()
+{
+    /*
+     * We can recurse only if there is at least TCL_WIN_STACK_THRESHOLD
+     * bytes of stack space left.  alloca() is cheap on windows; basically
+     * it just subtracts from the stack pointer causing the OS to throw an
+     * exception if the stack pointer is set below the bottom of the stack.
+     */
+
+    try {
+	alloca(TCL_WIN_STACK_THRESHOLD);
+	return 1;
+    } except (1) {}
+
+    return 0;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
  * TclWinGetPlatformId --
  *
  *	Determines whether running under NT, 95, or Win32s, to allow 
diff --git a/win/tclWinInt.h b/win/tclWinInt.h
index 4169472..64c43f7 100644
--- a/win/tclWinInt.h
+++ b/win/tclWinInt.h
@@ -8,7 +8,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclWinInt.h,v 1.5 1998/09/14 18:40:20 stanton Exp $
+ * RCS: @(#) $Id: tclWinInt.h,v 1.5.4.1 1999/03/04 00:59:04 stanton Exp $
  */
 
 #ifndef _TCLWININT
@@ -27,6 +27,14 @@
 #endif
 
 /*
+ * The following specifies how much stack space TclpCheckStackSpace()
+ * ensures is available.  TclpCheckStackSpace() is called by Tcl_EvalObj()
+ * to help avoid overflowing the stack in the case of infinite recursion.
+ */
+
+#define TCL_WIN_STACK_THRESHOLD 0x2000
+
+/*
  * Some versions of Borland C have a define for the OSVERSIONINFO for
  * Win32s and for NT, but not for Windows 95.
  */