[alsa-devel] crash with assertion (?)

[IOhannes m zmoelnig]

On 2010-09-07 19:06, Clemens Ladisch wrote:
> IOhannes m zmoelnig wrote:
>> i'm requesting my "plughw" device with 44100Hz
>> the request is done with something like:
>>  rate=44100;
>>  err = snd_pcm_hw_params_set_rate_min(handle, params, &rate, 0);
> 
> This requests a sample rate of at least 44100 Hz.

yes. this is good enough for me.
(it shouldn't crash though)

> 
>> [...]
>>  err = snd_pcm_hw_params(handle, params);
>>
>> what happens:
>> in the snd_pcm_hw_params(), my program exits with:
>> "interval_inline.h:52: snd_interval_single: Assertion
>> `!snd_interval_empty(i)' failed."
> 
> You called snd_pcm_hw_params with an invalid params structure.
> I'd guess that snd_pcm_hw_params_set_rate_min (or some other
> snd_pcm_hw_params_set_*) returned an error.

i wish you were right.
however, it seems like i am blindfolded.

i noticed however, that i need to set both the rate (i use
snd_pcm_hw_params_set_rate_min()) and the period size (i use
snd_pcm_hw_params_set_period_size_near()), in order to make it crash.

attached is an example code that triggers the crash.
please someone shed some light...

gmasdr
IOhannes


PS: that's how i use the sample program:
$ gcc -o alsatest alsatest.c $(pkg-config --cflags --libs alsa)
$ ./alsatest
trying to open 'hw:0' as CAPTURE
configuring device succeeded
CAPTURE configured
trying to open 'hw:0' as PLAYBACK
configuring device succeeded
PLAYBACK configured
trying to open 'plughw:0' as CAPTURE
configuring device succeeded
CAPTURE configured
trying to open 'plughw:0' as PLAYBACK
alsatest: interval_inline.h:55: snd_interval_single: Assertion
`!snd_interval_empty(i)' failed.
Aborted

so it seems to work fine with "hw:0" but not with "plughw:0".

you can specify the device to be opened on the cmdline:
$ ./alsatest hw:2
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