ioctl(arg) - uninitialised byte(s) in alsa lib

ioctl(arg) - uninitialised byte(s) in alsa lib

[Mathieu Monney]

Hi all,

I'm currently working on a small audio stack on top of alsa and I'm 
getting some "Syscall param ioctl(arg) contains uninitialized byte(s)" 
errors when I run my program using valgrind. I don't know if it is a bug 
in my program or in alsa lib. What I'm sure is that my program is 
working even though these errors appear.

The dump:

==14279== Syscall param ioctl(arg) contains uninitialised byte(s)
==14279==    at 0x40007F2: (within /lib/ld-2.6.1.so)
==14279==    by 0x40DE911: snd_pcm_prepare (in /usr/lib/libasound.so.2.0.0)
==14279==    by 0x40F2552: (within /usr/lib/libasound.so.2.0.0)
==14279==    by 0x40DE911: snd_pcm_prepare (in /usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4F0C: snd_pcm_hw_params (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x80A6599: AlsaConfigureDevice (in 
/home/mathieu/BProject/WiFi-VoIP/pjsip/pjsip_host_x86/pjsip-apps/bin/pjsua-i686-pc-linux-gnu)
==14279==    by 0x80A6DE3: pjmedia_snd_open (in 
/home/mathieu/BProject/WiFi-VoIP/pjsip/pjsip_host_x86/pjsip-apps/bin/pjsua-i686-pc-linux-gnu)
==14279==    by 0x809EC85: start_sound_device (in 
/home/mathieu/BProject/WiFi-VoIP/pjsip/pjsip_host_x86/pjsip-apps/bin/pjsua-i686-pc-linux-gnu)
==14279==    by 0x805EE1E: pjsua_set_snd_dev (in 
/home/mathieu/BProject/WiFi-VoIP/pjsip/pjsip_host_x86/pjsip-apps/bin/pjsua-i686-pc-linux-gnu)
==14279==    by 0x80615AA: pjsua_media_subsys_start (in 
/home/mathieu/BProject/WiFi-VoIP/pjsip/pjsip_host_x86/pjsip-apps/bin/pjsua-i686-pc-linux-gnu)
==14279==    by 0x805AAC5: pjsua_start (in 
/home/mathieu/BProject/WiFi-VoIP/pjsip/pjsip_host_x86/pjsip-apps/bin/pjsua-i686-pc-linux-gnu)
==14279==    by 0x805001B: app_main (in 
/home/mathieu/BProject/WiFi-VoIP/pjsip/pjsip_host_x86/pjsip-apps/bin/pjsua-i686-pc-linux-gnu)
==14279==
==14279== Syscall param ioctl(arg) contains uninitialised byte(s)
==14279==    at 0x40007F2: (within /lib/ld-2.6.1.so)
==14279==    by 0x40DE911: snd_pcm_prepare (in /usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4F0C: snd_pcm_hw_params (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x411C213: snd_pcm_direct_initialize_slave (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x4115DFB: snd_pcm_dmix_open (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x4116286: _snd_pcm_dmix_open (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4384: (within /usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4A82: (within /usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4AF2: snd_pcm_open_slave (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x4100CEF: _snd_pcm_plug_open (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4384: (within /usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4A82: (within /usr/lib/libasound.so.2.0.0)
==14279==
==14279== Syscall param ioctl(arg) contains uninitialised byte(s)
==14279==    at 0x40007F2: (within /lib/ld-2.6.1.so)
==14279==    by 0x40DE7D1: snd_pcm_start (in /usr/lib/libasound.so.2.0.0)
==14279==    by 0x411C5DF: snd_pcm_direct_initialize_slave (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x4115DFB: snd_pcm_dmix_open (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x4116286: _snd_pcm_dmix_open (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4384: (within /usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4A82: (within /usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4AF2: snd_pcm_open_slave (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x4100CEF: _snd_pcm_plug_open (in 
/usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4384: (within /usr/lib/libasound.so.2.0.0)
==14279==    by 0x40E4A82: (within /usr/lib/libasound.so.2.0.0)
==14279==    by 0x80A6E1B: pjmedia_snd_open (in 
/home/mathieu/BProject/WiFi-VoIP/pjsip/pjsip_host_x86/pjsip-apps/bin/pjsua-i686-pc-linux-gnu)

Thank you,

Mathieu Monney

Re: ioctl(arg) - uninitialised byte(s) in alsa lib

[Clemens Ladisch]

Mathieu Monney wrote:
> I'm currently working on a small audio stack on top of alsa and I'm
> getting some "Syscall param ioctl(arg) contains uninitialized byte(s)"
> errors when I run my program using valgrind.
>
> ==14279==    by 0x40DE911: snd_pcm_prepare (in /usr/lib/libasound.so.2.0.0)

The ioctl call is in src/pcm/pcm_hw.c:

	if (ioctl(fd, SNDRV_PCM_IOCTL_PREPARE) < 0) {

Apparently, valgrind doesn't detect the cases where there is no third
argument.


Regards,
Clemens