params_free functions don't work

[imyxh]

The following code segfaults on the call to snd_pcm_hw_params_free on my machine:

#include <alsa/asoundlib.h>
void main() {
    snd_pcm_hw_params_t *params;
    snd_pcm_hw_params_alloca(&params);
    snd_pcm_hw_params_free(params);
}

The same goes for s/hw/sw/g. Am I doing something wrong? In more complex examples it seems to fail with munmap_chunk complaining about an invalid pointer, or free complaining about an invalid size.

How are the *_params_free functions meant to be used?

[perexg]

The free functions are for mallocated memory - snd_pcm_hw_params_malloc. The alloca variants use stack (see man alloca for the storage, thus this space is freed automatically when the caller function exits).

[imyxh]

Ah. That'll do it. I wasn't familiar with alloca and assumed that _params_alloca was just a funny way to say _params_malloc. Thanks for explaining.