expr: Fix refcount issue converting invalid boolean

Reported-by: Ryan Whitworth <me@ryanwhitworth.com>
Signed-off-by: Steve Bennett <steveb@workware.net.au>

jim.c

@@ -8240,17 +8240,23 @@ static int ExprBool(Jim_Interp *interp, Jim_Obj *obj)
     long l;
     double d;
     int b;
+    int ret = -1;
+
+    /* In case the object is interp->result with refcount 1*/
+    Jim_IncrRefCount(obj);
 
     if (Jim_GetLong(interp, obj, &l) == JIM_OK) {
-        return l != 0;
+        ret = (l != 0);
     }
-    if (Jim_GetDouble(interp, obj, &d) == JIM_OK) {
-        return d != 0;
+    else if (Jim_GetDouble(interp, obj, &d) == JIM_OK) {
+        ret = (d != 0);
     }
-    if (Jim_GetBoolean(interp, obj, &b) == JIM_OK) {
-        return b != 0;
+    else if (Jim_GetBoolean(interp, obj, &b) == JIM_OK) {
+        ret = (b != 0);
     }
-    return -1;
+
+    Jim_DecrRefCount(interp, obj);
+    return ret;
 }
 
 static int JimExprOpAnd(Jim_Interp *interp, struct JimExprNode *node)

regtest.tcl

@@ -345,6 +345,11 @@ puts "TEST 49 PASSED"
 catch {expr {>>-$x}}
 puts "TEST 50 PASSED"
 
+# REGTEST 51
+# expr convert invalid value to boolean
+catch {expr {2 && "abc$"}}
+puts "TEST 51 PASSED"
+
 # TAKE THE FOLLOWING puts AS LAST LINE
 
 puts "--- ALL TESTS PASSED ---"