jscript: Return undefined for empty RegExp captures in ES5+ mode.

dlls/jscript/jsregexp.c

@@ -361,17 +361,22 @@ static HRESULT create_match_array(script_ctx_t *ctx, jsstr_t *input_str,
         return hres;
 
     for(i=0; i < result->paren_count; i++) {
-        if(result->parens[i].index != -1)
-            str = jsstr_substr(input_str, result->parens[i].index, result->parens[i].length);
-        else
-            str = jsstr_empty();
-        if(!str) {
+        jsval_t val;
+
+        if(result->parens[i].index != -1) {
+            if(!(str = jsstr_substr(input_str, result->parens[i].index, result->parens[i].length))) {
                 hres = E_OUTOFMEMORY;
                 break;
             }
+            val = jsval_string(str);
+        }else if(ctx->version < SCRIPTLANGUAGEVERSION_ES5) {
+            val = jsval_string(jsstr_empty());
+        }else {
+            val = jsval_undefined();
+        }
 
-        hres = jsdisp_propput_idx(array, i+1, jsval_string(str));
-        jsstr_release(str);
+        hres = jsdisp_propput_idx(array, i+1, val);
+        jsval_release(val);
         if(FAILED(hres))
             break;
     }

dlls/jscript/tests/regexp.js

@@ -625,6 +625,18 @@ ok(tmp === "x*y", '"x/y".replace(/[/]/, "*") = ' + tmp);
 tmp = "x/y".replace(/[xy/]/g, "*");
 ok(tmp === "***", '"x/y".replace(/[xy/]/, "*") = ' + tmp);
 
+tmp = /()/.exec("")[1];
+ok(tmp === "", "/()/ captured: " + tmp);
+tmp = /()?/.exec("")[1];
+ok(tmp === "", "/()?/ captured: " + tmp);
+tmp = /()??/.exec("")[1];
+ok(tmp === "", "/()??/ captured: " + tmp);
+tmp = /()*/.exec("")[1];
+ok(tmp === "", "/()*/ captured: " + tmp);
+tmp = /()??()/.exec("");
+ok(tmp[1] === "", "/()??()/ [1] captured: " + tmp);
+ok(tmp[2] === "", "/()??()/ [2] captured: " + tmp);
+
 /(b)/.exec("abc");
 ok(RegExp.$1 === "b", "RegExp.$1 = " + RegExp.$1);
 ok("$2" in RegExp, "RegExp.$2 doesn't exist");

dlls/mshtml/tests/es5.js

@@ -1610,6 +1610,22 @@ sync_test("isFrozen", function() {
     }
 });
 
+sync_test("RegExp", function() {
+    var r;
+
+    r = /()/.exec("")[1];
+    ok(r === "", "/()/ captured: " + r);
+    r = /()?/.exec("")[1];
+    ok(r === undefined, "/()?/ captured: " + r);
+    r = /()??/.exec("")[1];
+    ok(r === undefined, "/()??/ captured: " + r);
+    r = /()*/.exec("")[1];
+    ok(r === undefined, "/()*/ captured: " + r);
+    r = /()??()/.exec("");
+    ok(r[1] === undefined, "/()??()/ [1] captured: " + r);
+    ok(r[2] === "", "/()??()/ [2] captured: " + r);
+});
+
 sync_test("builtin_context", function() {
     var nullDisp = external.nullDisp;
     var tests = [