win32: add COM-specific SAFE_RELEASE to windows_utils.h

See: https://msdn.microsoft.com/en-us/library/windows/desktop/dd743946.aspx

Microsoft example code often uses a SAFE_RELEASE macro like the one in
the above link. This makes it easier to avoid errors when releasing COM
interfaces. It also reduces noise in COM-heavy code.

ao_wasapi.h also had a macro called SAFE_RELEASE, though unlike the
version above, its SAFE_RELEASE macro accepted a second parameter which
allowed it to destroy arbitrary objects other than just COM interfaces.
This renames ao_wasapi's SAFE_RELEASE to SAFE_DESTROY, which should more
accurately reflect what it does and prevent confusion with the Microsoft
version.

audio/out/ao_wasapi.c

@@ -255,9 +255,9 @@ static void uninit(struct ao *ao)
                "while waiting for audio thread to terminate\n");
     }
 
-    SAFE_RELEASE(state->hInitDone,   CloseHandle(state->hInitDone));
-    SAFE_RELEASE(state->hWake,       CloseHandle(state->hWake));
-    SAFE_RELEASE(state->hAudioThread,CloseHandle(state->hAudioThread));
+    SAFE_DESTROY(state->hInitDone,   CloseHandle(state->hInitDone));
+    SAFE_DESTROY(state->hWake,       CloseHandle(state->hWake));
+    SAFE_DESTROY(state->hAudioThread,CloseHandle(state->hAudioThread));
 
     wasapi_change_uninit(ao);
 
@@ -305,7 +305,7 @@ static int init(struct ao *ao)
     }
 
     WaitForSingleObject(state->hInitDone, INFINITE); // wait on init complete
-    SAFE_RELEASE(state->hInitDone,CloseHandle(state->hInitDone));
+    SAFE_DESTROY(state->hInitDone,CloseHandle(state->hInitDone));
     if (FAILED(state->init_ret)) {
         if (!ao->probing)
             MP_FATAL(ao, "Received failure from audio thread\n");
@@ -418,10 +418,10 @@ static int thread_control(struct ao *ao, enum aocontrol cmd, void *arg)
         do {
             IAudioSessionControl_SetDisplayName(state->pSessionControl, title, NULL);
 
-            SAFE_RELEASE(tmp, CoTaskMemFree(tmp));
+            SAFE_DESTROY(tmp, CoTaskMemFree(tmp));
             IAudioSessionControl_GetDisplayName(state->pSessionControl, &tmp);
         } while (lstrcmpW(title, tmp));
-        SAFE_RELEASE(tmp, CoTaskMemFree(tmp));
+        SAFE_DESTROY(tmp, CoTaskMemFree(tmp));
         talloc_free(title);
         return CONTROL_OK;
     }

audio/out/ao_wasapi.h

@@ -47,7 +47,7 @@ void wasapi_change_uninit(struct ao* ao);
 
 #define EXIT_ON_ERROR(hres)  \
               do { if (FAILED(hres)) { goto exit_label; } } while(0)
-#define SAFE_RELEASE(unk, release) \
+#define SAFE_DESTROY(unk, release) \
               do { if ((unk) != NULL) { release; (unk) = NULL; } } while(0)
 
 #define mp_format_res_str(hres) \

audio/out/ao_wasapi_changenotify.c

@@ -242,5 +242,5 @@ void wasapi_change_uninit(struct ao *ao)
             change->pEnumerator, (IMMNotificationClient *)change);
     }
 
-    SAFE_RELEASE(change->pEnumerator, IMMDeviceEnumerator_Release(change->pEnumerator));
+    SAFE_RELEASE(change->pEnumerator);
 }

audio/out/ao_wasapi_utils.c

@@ -539,8 +539,7 @@ static void init_session_display(struct wasapi_state *state) {
     return;
 exit_label:
     // if we got here then the session control is useless - release it
-    SAFE_RELEASE(state->pSessionControl,
-                 IAudioSessionControl_Release(state->pSessionControl));
+    SAFE_RELEASE(state->pSessionControl);
     MP_WARN(state, "Error setting audio session display name: %s\n",
             mp_HRESULT_to_str(hr));
     return;
@@ -571,10 +570,8 @@ static void init_volume_control(struct wasapi_state *state)
     return;
 exit_label:
     state->vol_hw_support = 0;
-    SAFE_RELEASE(state->pEndpointVolume,
-                 IAudioEndpointVolume_Release(state->pEndpointVolume));
-    SAFE_RELEASE(state->pAudioVolume,
-                 ISimpleAudioVolume_Release(state->pAudioVolume));
+    SAFE_RELEASE(state->pEndpointVolume);
+    SAFE_RELEASE(state->pAudioVolume);
     MP_WARN(state, "Error setting up volume control: %s\n",
             mp_HRESULT_to_str(hr));
 }
@@ -707,7 +704,7 @@ exit_label:
     if (FAILED(hr))
         mp_warn(l, "Failed getting device name: %s\n", mp_HRESULT_to_str(hr));
     PropVariantClear(&devname);
-    SAFE_RELEASE(pProps, IPropertyStore_Release(pProps));
+    SAFE_RELEASE(pProps);
     return namestr ? namestr : talloc_strdup(talloc_ctx, "");
 }
 
@@ -722,7 +719,7 @@ static struct device_desc *get_device_desc(struct mp_log *l, IMMDevice *pDevice)
     struct device_desc *d = talloc_zero(NULL, struct device_desc);
     d->deviceID = talloc_memdup(d, deviceID,
                                 (wcslen(deviceID) + 1) * sizeof(wchar_t));
-    SAFE_RELEASE(deviceID, CoTaskMemFree(deviceID));
+    SAFE_DESTROY(deviceID, CoTaskMemFree(deviceID));
 
     char *full_id = mp_to_utf8(NULL, d->deviceID);
     bstr id = bstr0(full_id);
@@ -745,8 +742,8 @@ static void destroy_enumerator(struct enumerator *e)
 {
     if (!e)
         return;
-    SAFE_RELEASE(e->pDevices, IMMDeviceCollection_Release(e->pDevices));
-    SAFE_RELEASE(e->pEnumerator, IMMDeviceEnumerator_Release(e->pEnumerator));
+    SAFE_RELEASE(e->pDevices);
+    SAFE_RELEASE(e->pEnumerator);
     talloc_free(e);
 }
 
@@ -782,7 +779,7 @@ static struct device_desc *device_desc_for_num(struct enumerator *e, UINT i)
         return NULL;
     }
     struct device_desc *d = get_device_desc(e->log, pDevice);
-    SAFE_RELEASE(pDevice, IMMDevice_Release(pDevice));
+    SAFE_RELEASE(pDevice);
     return d;
 }
 
@@ -797,7 +794,7 @@ static struct device_desc *default_device_desc(struct enumerator *e)
         return NULL;
     }
     struct device_desc *d = get_device_desc(e->log, pDevice);
-    SAFE_RELEASE(pDevice, IMMDevice_Release(pDevice));
+    SAFE_RELEASE(pDevice);
     return d;
 }
 
@@ -834,7 +831,7 @@ static HRESULT load_device(struct mp_log *l,
 exit_label:
     if (FAILED(hr))
         mp_err(l, "Error loading selected device: %s\n", mp_HRESULT_to_str(hr));
-    SAFE_RELEASE(pEnumerator, IMMDeviceEnumerator_Release(pEnumerator));
+    SAFE_RELEASE(pEnumerator);
     return hr;
 }
 
@@ -908,7 +905,7 @@ LPWSTR wasapi_find_deviceID(struct ao *ao)
                         BSTR_P(device), d->id, d->name);
             }
         }
-        SAFE_RELEASE(d, talloc_free(d));
+        SAFE_DESTROY(d, talloc_free(d));
     }
 
     if (!deviceID)
@@ -969,13 +966,13 @@ void wasapi_thread_uninit(struct ao *ao)
     if (state->pAudioClient)
         IAudioClient_Stop(state->pAudioClient);
 
-    SAFE_RELEASE(state->pRenderClient,   IAudioRenderClient_Release(state->pRenderClient));
-    SAFE_RELEASE(state->pAudioClock,     IAudioClock_Release(state->pAudioClock));
-    SAFE_RELEASE(state->pAudioVolume,    ISimpleAudioVolume_Release(state->pAudioVolume));
-    SAFE_RELEASE(state->pEndpointVolume, IAudioEndpointVolume_Release(state->pEndpointVolume));
-    SAFE_RELEASE(state->pSessionControl, IAudioSessionControl_Release(state->pSessionControl));
-    SAFE_RELEASE(state->pAudioClient,    IAudioClient_Release(state->pAudioClient));
-    SAFE_RELEASE(state->pDevice,         IMMDevice_Release(state->pDevice));
-    SAFE_RELEASE(state->hTask,           AvRevertMmThreadCharacteristics(state->hTask));
+    SAFE_RELEASE(state->pRenderClient);
+    SAFE_RELEASE(state->pAudioClock);
+    SAFE_RELEASE(state->pAudioVolume);
+    SAFE_RELEASE(state->pEndpointVolume);
+    SAFE_RELEASE(state->pSessionControl);
+    SAFE_RELEASE(state->pAudioClient);
+    SAFE_RELEASE(state->pDevice);
+    SAFE_DESTROY(state->hTask, AvRevertMmThreadCharacteristics(state->hTask));
     MP_DBG(ao, "Thread uninit done\n");
 }

osdep/windows_utils.h

@@ -20,6 +20,10 @@
 
 #include <windows.h>
 
+// Conditionally release a COM interface and set the pointer to NULL
+#define SAFE_RELEASE(u) \
+    do { if ((u) != NULL) (u)->lpVtbl->Release(u); (u) = NULL; } while(0)
+
 char *mp_GUID_to_str_buf(char *buf, size_t buf_size, const GUID *guid);
 #define mp_GUID_to_str(guid) mp_GUID_to_str_buf((char[40]){0}, 40, (guid))
 char *mp_HRESULT_to_str_buf(char *buf, size_t buf_size, HRESULT hr);