There is a complain from Valgrind about invalid memory access in snd_device_name_hint(-1, ..) // ...

media/audio/linux/audio_manager_linux.cc

Index: media/audio/linux/audio_manager_linux.cc
===================================================================
--- media/audio/linux/audio_manager_linux.cc	(revision 100401)
+++ media/audio/linux/audio_manager_linux.cc	(working copy)
@@ -63,25 +63,29 @@
   }
 
   // Constants specified by the ALSA API for device hints.
-  static const int kGetAllDevices = -1;
   static const char kPcmInterfaceName[] = "pcm";
   bool has_device = false;
   void** hints = NULL;
+  int card = -1;
 
-  // Use the same approach to find the devices as in
-  // AlsaPcmOutputStream::FindDeviceForChannels
-  // Get Alsa device hints.
-  int error = wrapper_->DeviceNameHint(kGetAllDevices,
-                                       kPcmInterfaceName,
-                                       &hints);
-  if (error == 0) {
-    has_device = HasAnyValidAudioInputDevice(hints);
-  } else {
-    LOG(ERROR) << "Unable to get device hints: " << wrapper_->StrError(error);
+  // Loop through the sound cards to get Alsa device hints.
+  // Don't use snd_device_name_hint(-1,..) since there is a memory leak inside

[Alexander Potapenko, 2011/09/13 17:03:04]

There is not a memory leak, but an access violation inside that ALSA API. Please
fix the comment.

[xians, 2011/09/14 08:12:01]

Done.

+  // this ALSA API with libasound.so.2.0.0.
+  while (!wrapper_->CardNext(&card) && (card >= 0) && !has_device) {
+    int error = wrapper_->DeviceNameHint(card,
+                                         kPcmInterfaceName,
+                                         &hints);
+    if (error == 0) {
+      has_device = HasAnyValidAudioInputDevice(hints);
+
+      // Destroy the hints now that we're done with it.
+      wrapper_->DeviceNameFreeHint(hints);
+      hints = NULL;
+    } else {
+      LOG(ERROR) << "Unable to get device hints: " << wrapper_->StrError(error);
+    }
   }
 
-  // Destroy the hint now that we're done with it.
-  wrapper_->DeviceNameFreeHint(hints);

[Raymond Toy (Google), 2011/09/13 17:07:40]

Won't there be a real leak now since you don't free hints anymore?

[xians, 2011/09/14 08:12:01]

In case DeviceNameHint fails, hints should be always NULL, so it is all right
not to call DeviceNameFreeHint. Of course, it is also safe to call it since ALSA
takes care of the case when hints==NULL.

   return has_device;
 }