[alsa-devel] Plug In Creation - aplay can't find existing .so

[Brandon Yates]

Actually on close inspection it looks like open is succeeding. Not sure
what's going on here. Here's more of the strace:


open("/usr/lib/i386-linux-gnu/alsa-lib/libasound_module_pcm_adt_dsp.so",
O_RDONLY|O_CLOEXEC) = 3
read(3,
"\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\20\7\0\0004\0\0\0"...,
512) = 512
fstat64(3, {st_mode=S_IFREG|0644, st_size=7655, ...}) = 0
mmap2(NULL, 8464, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0)
= 0x166000
mmap2(0x167000, 8192, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0) = 0x167000
close(3)                                = 0
munmap(0x166000, 8464)                  = 0
write(2, "ALSA lib dlmisc.c:254:(snd1_dlob"..., 45ALSA lib
dlmisc.c:254:(snd1_dlobj_cache_get) ) = 45
write(2, "Cannot open shared library /usr/"..., 91Cannot open shared
library
/usr/lib/i386-linux-gnu/alsa-lib/libasound_module_pcm_adt_dsp.so) = 91


Any insight?

-----Original Message-----
From: Takashi Iwai [mailto:tiwai at suse.de] 
Sent: Friday, June 13, 2014 8:42 AM
To: Brandon Yates
Cc: alsa-devel at alsa-project.org
Subject: Re: [alsa-devel] Plug In Creation - aplay can't find existing
.so

At Tue, 10 Jun 2014 13:55:39 -0400,
Brandon Yates wrote:
> 
> Hello,
> 
> I am working on a new pcm plugin. At this point it is basically just a

> Hello World plugin, to make sure I have the tools working and 
> understand the workflow.  I created a simple file which is just
basically:
> 
> #include <alsa/asoundlib.h>
> #include <alsa/pcm_external.h>
> SND_PCM_PLUGIN_DEFINE_FUNC(my_mod)
> {	
>    printf("hello world\n");
>    return 0;
> }
> SND_PCM_PLUGIN_SYMBOL(my_mod);
> 
> 
> I compiled this as a shared lib named
'libasound_module_pcm_my_mod.so'
> and copied it to '/usr/lib/i386-linux-gnu/alsa-lib/'
> 
> I edited my ~/.asoundrc to create a new device that uses this plugin.
> Then I try to use it with `aplay --device=my_mod_test out.pcm`
> 
> I get the error message
> 
> ALSA lib dlmisc.c:254:(snd1_dlobj_cache_get) Cannot open shared 
> library 
> /usr/lib/i386-linux-gnu/alsa-lib/libasound_module_pcm_my_mod.so
> aplay: main:682: audio open error: No such device or address
> 
> 
> But this file actually does exist, I just copied it there.
> 
> 
> Any idea why this happens?

Try strace to see what happens.  If it fails in dlopen(), it's likely
because your shared object is invalid.


Takashi