mfreadwrite/writer: Make sure output pointer is initialized.

dlls/mfreadwrite/tests/mfplat.c

@@ -1299,8 +1299,18 @@ static void test_sink_writer(void)
     hr = MFCreateSinkWriterFromURL(NULL, NULL, NULL, NULL);
     ok(hr == E_INVALIDARG, "Unexpected hr %#lx.\n", hr);
 
+    writer = (void *)0xdeadbeef;
     hr = MFCreateSinkWriterFromURL(NULL, NULL, NULL, &writer);
     ok(hr == E_INVALIDARG, "Unexpected hr %#lx.\n", hr);
+    ok(!writer, "Unexpected pointer %p.\n", writer);
+
+    hr = MFCreateSinkWriterFromMediaSink(NULL, NULL, NULL);
+    ok(hr == E_INVALIDARG, "Unexpected hr %#lx.\n", hr);
+
+    writer = (void *)0xdeadbeef;
+    hr = MFCreateSinkWriterFromMediaSink(NULL, NULL, &writer);
+    ok(hr == E_INVALIDARG, "Unexpected hr %#lx.\n", hr);
+    ok(!writer, "Unexpected pointer %p.\n", writer);
 }
 
 START_TEST(mfplat)

dlls/mfreadwrite/writer.c

@@ -186,6 +186,11 @@ HRESULT create_sink_writer_from_sink(IMFMediaSink *sink, IMFAttributes *attribut
     struct sink_writer *object;
     HRESULT hr;
 
+    *out = NULL;
+
+    if (!sink)
+        return E_INVALIDARG;
+
     object = malloc(sizeof(*object));
     if (!object)
         return E_OUTOFMEMORY;
@@ -205,6 +210,9 @@ HRESULT WINAPI MFCreateSinkWriterFromMediaSink(IMFMediaSink *sink, IMFAttributes
 {
     TRACE("%p, %p, %p.\n", sink, attributes, writer);
 
+    if (!writer)
+        return E_INVALIDARG;
+
     return create_sink_writer_from_sink(sink, attributes, &IID_IMFSinkWriter, (void **)writer);
 }
 
@@ -289,6 +297,8 @@ HRESULT create_sink_writer_from_url(const WCHAR *url, IMFByteStream *bytestream,
     CLSID clsid;
     HRESULT hr;
 
+    *out = NULL;
+
     if (!url && !bytestream)
         return E_INVALIDARG;
 
@@ -332,5 +342,8 @@ HRESULT WINAPI MFCreateSinkWriterFromURL(const WCHAR *url, IMFByteStream *bytest
 {
     TRACE("%s, %p, %p, %p.\n", debugstr_w(url), bytestream, attributes, writer);
 
+    if (!writer)
+        return E_INVALIDARG;
+
     return create_sink_writer_from_url(url, bytestream, attributes, &IID_IMFSinkWriter, (void **)writer);
 }