dwmapi: Check NULL parameter in DwmIsCompositionEnabled().

configure

@@ -20756,6 +20756,7 @@ wine_fn_config_makefile dlls/dsuiext enable_dsuiext
 wine_fn_config_makefile dlls/dswave enable_dswave
 wine_fn_config_makefile dlls/dswave/tests enable_tests
 wine_fn_config_makefile dlls/dwmapi enable_dwmapi
+wine_fn_config_makefile dlls/dwmapi/tests enable_tests
 wine_fn_config_makefile dlls/dwrite enable_dwrite
 wine_fn_config_makefile dlls/dwrite/tests enable_tests
 wine_fn_config_makefile dlls/dx8vb enable_dx8vb

configure.ac

@@ -3278,6 +3278,7 @@ WINE_CONFIG_MAKEFILE(dlls/dsuiext)
 WINE_CONFIG_MAKEFILE(dlls/dswave)
 WINE_CONFIG_MAKEFILE(dlls/dswave/tests)
 WINE_CONFIG_MAKEFILE(dlls/dwmapi)
+WINE_CONFIG_MAKEFILE(dlls/dwmapi/tests)
 WINE_CONFIG_MAKEFILE(dlls/dwrite)
 WINE_CONFIG_MAKEFILE(dlls/dwrite/tests)
 WINE_CONFIG_MAKEFILE(dlls/dx8vb)

dlls/dwmapi/dwmapi_main.c

@@ -60,6 +60,9 @@ HRESULT WINAPI DwmIsCompositionEnabled(BOOL *enabled)
     else
         TRACE("%p\n", enabled);
 
+    if (!enabled)
+        return E_INVALIDARG;
+
     *enabled = FALSE;
     return S_OK;
 }

dlls/dwmapi/tests/Makefile.in

+TESTDLL = dwmapi.dll
+IMPORTS = dwmapi
+
+C_SRCS = \
+	dwmapi.c

dlls/dwmapi/tests/dwmapi.c

+/*
+ * Copyright 2020 Zhiyi Zhang for CodeWeavers
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+#include "dwmapi.h"
+#include "wine/test.h"
+
+static void test_DwmIsCompositionEnabled(void)
+{
+    BOOL enabled;
+    HRESULT hr;
+
+    hr = DwmIsCompositionEnabled(NULL);
+    ok(hr == E_INVALIDARG, "Expected %#x, got %#x.\n", E_INVALIDARG, hr);
+
+    enabled = -1;
+    hr = DwmIsCompositionEnabled(&enabled);
+    ok(hr == S_OK, "Expected %#x, got %#x.\n", S_OK, hr);
+    ok(enabled == TRUE || enabled == FALSE, "Got unexpected %#x.\n", enabled);
+}
+
+START_TEST(dwmapi)
+{
+    test_DwmIsCompositionEnabled();
+}