On Mon, 2009-11-02 at 15:55 +0100, Takashi Iwai wrote:
> Thanks.  I guess this depends on the config files.
> Could you attach your ones?

I can reproduce with only the stock /usr/share/alsa/alsa.conf from
Debian installed if I try to use the "null" device after
snd_device_name_hint.  /usr/share/alsa/alsa.conf is attached.

------

#include <stdio.h>
#include <alsa/asoundlib.h>

void try_open (const char * pcm)
{
    snd_pcm_t * handle;
    int error;

    error = snd_pcm_open (& handle, pcm, SND_PCM_STREAM_PLAYBACK, 0);

    if (error < 0)
        printf ("Failed to open %s: %s.\n", pcm, snd_strerror (error));
    else
    {
        printf ("Opened %s.\n", pcm);
        snd_pcm_close (handle);
    }
}

int main (void)
{
    void * * hints;

    try_open ("default");
    try_open ("null");
    try_open ("default");
    try_open ("null");

    printf ("Calling snd_device_name_hint().\n");
    snd_device_name_hint (-1, "pcm", & hints);
    snd_device_name_free_hint (hints);

    try_open ("default");
    try_open ("null");
    try_open ("default");
    try_open ("null");

    return 0;
}

------

$ ./pcmtest 
Opened default.
Opened null.
Opened default.
Opened null.
Calling snd_device_name_hint().
Opened default.
ALSA lib pcm.c:2211:(snd_pcm_open_noupdate) Unknown PCM null
Failed to open null: No such file or directory.
Opened default.
ALSA lib pcm.c:2211:(snd_pcm_open_noupdate) Unknown PCM null
Failed to open null: No such file or directory.