From 773e53fd316eb916b885120ed4960368abec9acd Mon Sep 17 00:00:00 2001
From: dgp <dgp@users.sourceforge.net>
Date: Sat, 25 Mar 2006 16:58:38 +0000
Subject:         * generic/tclExecute.c: Corrections to INST_EXPON detection
 of         overflow to use mp_int calculations.

---
 ChangeLog            |  5 +++++
 generic/tclExecute.c | 12 ++++++++----
 tests/expr.test      |  3 ++-
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 778ea4f..fe60ad1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2006-03-25  Don Porter  <dgp@users.sourceforge.net>
+
+	* generic/tclExecute.c:	Corrections to INST_EXPON detection of
+	overflow to use mp_int calculations.
+
 2006-03-24  Kevin Kenny  <kennykb@acm.org>
 
 	* generic/tclExecute.c (TclExecuteByteCode): Added a couple
diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index 9b1f26e..65da821 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -12,7 +12,7 @@
  * 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 1.231 2006/03/24 19:05:40 kennykb Exp $
+ * RCS: @(#) $Id: tclExecute.c,v 1.232 2006/03/25 16:58:38 dgp Exp $
  */
 
 #include "tclInt.h"
@@ -4715,7 +4715,8 @@ TclExecuteByteCode(
 		    wResult -= 1;
 		}
 		break;
-	    case INST_EXPON:
+	    case INST_EXPON: {
+		int wasNegative;
 		if (w2 & 1) {
 		    wResult = w1;
 		} else {
@@ -4724,21 +4725,24 @@ TclExecuteByteCode(
 		w1 *= w1;
 		w2 /= 2;
 		for (; w2>Tcl_LongAsWide(1) ; w1*=w1,w2/=2) {
+		    wasNegative = (wResult < 0);
 		    if (w1 < 0) {
 			goto overflow;
 		    }
 		    if (w2 & 1) {
 			wResult *= w1;
-			if (wResult < 0) {
+			if (wasNegative != (wResult < 0)) {
 			    goto overflow;
 			}
 		    }
 		}
+		wasNegative = (wResult < 0);
 		wResult *=  w1;
-		if (wResult < 0) {
+		if (wasNegative != (wResult < 0)) {
 		    goto overflow;
 		}
 		break;
+	    }
 	    default:
 		/* Unused, here to silence compiler warning. */
 		wResult = 0;
diff --git a/tests/expr.test b/tests/expr.test
index f747f87..8f86e66 100644
--- a/tests/expr.test
+++ b/tests/expr.test
@@ -10,7 +10,7 @@
 # See the file "license.terms" for information on usage and redistribution
 # of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 #
-# RCS: @(#) $Id: expr.test,v 1.52 2006/03/24 18:20:37 dgp Exp $
+# RCS: @(#) $Id: expr.test,v 1.53 2006/03/25 16:58:38 dgp Exp $
 
 if {[lsearch [namespace children] ::tcltest] == -1} {
     package require tcltest 2.1
@@ -1031,6 +1031,7 @@ test expr-23.38 {INST_EXPON: big integer} {expr {10**19}} 1[string repeat 0 19]
 test expr-23.39 {INST_EXPON: big integer} {
     expr 1[string repeat 0 30]**2
 } 1[string repeat 0 60]
+test expr-23.40 {INST_EXPON: overflow to big integer} {expr {(-10)**3}} -1000
 
 # Some compilers get this wrong; ensure that we work around it correctly
 test expr-24.1 {expr edge cases; shifting} {expr int(5)>>32} 0
-- 
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