From 538960215f5f4a997697c5883187205825875944 Mon Sep 17 00:00:00 2001
From: "jan.nijtmans" <nijtmans@users.sourceforge.net>
Date: Thu, 17 Nov 2016 11:38:13 +0000
Subject: Add test-case for mp_iseven(). If mp_iseven(0) ever returns 0, we
 will be warned that we are using the wrong mp_iseven() function.

---
 generic/tclTestObj.c | 25 +++++++++++++++++++++++--
 generic/tclTomMath.h |  2 +-
 tests/obj.test       |  7 +++++++
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/generic/tclTestObj.c b/generic/tclTestObj.c
index 6053ae3..1cbe67a 100644
--- a/generic/tclTestObj.c
+++ b/generic/tclTestObj.c
@@ -152,10 +152,10 @@ TestbignumobjCmd(
     Tcl_Obj *const objv[])	/* Argument vector */
 {
     const char *const subcmds[] = {
-	"set",	    "get",	"mult10",	"div10", NULL
+	"set",	    "get",	"mult10",	"div10",	"iseven", NULL
     };
     enum options {
-	BIGNUM_SET, BIGNUM_GET,	BIGNUM_MULT10,	BIGNUM_DIV10
+	BIGNUM_SET, BIGNUM_GET,	BIGNUM_MULT10,	BIGNUM_DIV10,	BIGNUM_ISEVEN
     };
     int index, varIndex;
     const char *string;
@@ -274,6 +274,27 @@ TestbignumobjCmd(
 	} else {
 	    SetVarToObj(varPtr, varIndex, Tcl_NewBignumObj(&newValue));
 	}
+	break;
+
+    case BIGNUM_ISEVEN:
+	if (objc != 3) {
+	    Tcl_WrongNumArgs(interp, 2, objv, "varIndex");
+	    return TCL_ERROR;
+	}
+	if (CheckIfVarUnset(interp, varPtr,varIndex)) {
+	    return TCL_ERROR;
+	}
+	if (Tcl_GetBignumFromObj(interp, varPtr[varIndex],
+		&bignumValue) != TCL_OK) {
+	    return TCL_ERROR;
+	}
+	if (!Tcl_IsShared(varPtr[varIndex])) {
+	    Tcl_SetIntObj(varPtr[varIndex], mp_iseven(&bignumValue));
+	} else {
+	    SetVarToObj(varPtr, varIndex, Tcl_NewIntObj(mp_iseven(&bignumValue)));
+	}
+	mp_clear(&bignumValue);
+	break;
     }
 
     Tcl_SetObjResult(interp, varPtr[varIndex]);
diff --git a/generic/tclTomMath.h b/generic/tclTomMath.h
index 6b96d2c..9b899fe 100644
--- a/generic/tclTomMath.h
+++ b/generic/tclTomMath.h
@@ -243,7 +243,7 @@ int mp_init_size(mp_int *a, int size);
 
 /* ---> Basic Manipulations <--- */
 #define mp_iszero(a) (((a)->used == 0) ? MP_YES : MP_NO)
-#define mp_iseven(a) ((((a)->used > 0) && (((a)->dp[0] & 1u) == 0u)) ? MP_YES : MP_NO)
+#define mp_iseven(a) ((((a)->used == 0) || (((a)->dp[0] & 1u) == 0u)) ? MP_YES : MP_NO)
 #define mp_isodd(a)  ((((a)->used > 0) && (((a)->dp[0] & 1u) == 1u)) ? MP_YES : MP_NO)
 #define mp_isneg(a)  (((a)->sign != MP_ZPOS) ? MP_YES : MP_NO)
 
diff --git a/tests/obj.test b/tests/obj.test
index a8d2d20..c354d69 100644
--- a/tests/obj.test
+++ b/tests/obj.test
@@ -625,6 +625,13 @@ test obj-33.7 {integer overflow on input} {
     list [string is integer $x] [expr { wide($x) }]
 } {0 -4294967296}
 
+test obj-34.1 {mp_iseven} testobj {
+    set result ""
+    lappend result [testbignumobj set 1 0]
+    lappend result [testbignumobj iseven 1]    ;
+    lappend result [testobj type 1]
+} {0 1 int}
+
 if {[testConstraint testobj]} {
     testobj freeallvars
 }
-- 
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