hw_params from shared library problem

hw_params from shared library problem

[Gerald Grabner]

Hi everybody,

I'm wondering how to correctly build a shared library using alsa
pcm. Setting the hardware parameters in a function which is part of a
shared library produces an error, snd_pcm_hw_params gives "invalid
argument". The example below with three primitive files (main file,
header and function code) illustrates the problem. With a static
library, everything works fine.

My system: gcc 3.4.6 on Gentoo with alsa 1.0.11.

Does anybody have an idea about the cause of this problem or how to 
solve it?

Many thanks,
Gerald

***

main.c:
   #include "object.h"
   int main()
   {
     object () ;
     return 0;
   }

object.h:
   void object();

object.c:
   #include <alsa/asoundlib.h>
   #include "object.h"
   void object ()
   {
     snd_pcm_t* pcm;
     snd_pcm_hw_params_t* hwparams;
     int rc;
     unsigned int rate = 44100;
     unsigned int channels = 2;
     int dir = 0;
     if ( snd_pcm_open(&pcm, "default", SND_PCM_STREAM_PLAYBACK, 0) < 0 )
       printf("Cannot open pcm.\n");
     snd_pcm_hw_params_alloca(&hwparams);
     snd_pcm_hw_params_any(pcm, hwparams);
     snd_pcm_hw_params_set_access(pcm, hwparams, 
SND_PCM_ACCESS_RW_INTERLEAVED);
     snd_pcm_hw_params_set_format(pcm, hwparams, SND_PCM_FORMAT_S16_LE);
     snd_pcm_hw_params_set_channels (pcm, hwparams, channels);
     snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, &dir);
     rc = snd_pcm_hw_params(pcm, hwparams) ;
     if ( rc < 0 )
       printf("Error setting hw params: %s.\n", snd_strerror(rc));
   }

Compilation:
   gcc -c -fPIC object.c
   gcc -shared -fPIC -o libTest.so object.o
   gcc -o main main.c -L. -lTest -lasound

Output:
   Error setting hw params: Invalid argument.

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Re: hw_params from shared library problem

[Lee Revell]

On Mon, 2006-06-26 at 23:11 +0200, Gerald Grabner wrote:
> Hi everybody,
> 
> I'm wondering how to correctly build a shared library using alsa
> pcm. Setting the hardware parameters in a function which is part of a
> shared library produces an error, snd_pcm_hw_params gives "invalid
> argument". The example below with three primitive files (main file,
> header and function code) illustrates the problem. With a static
> library, everything works fine.
> 
> My system: gcc 3.4.6 on Gentoo with alsa 1.0.11.
> 
> Does anybody have an idea about the cause of this problem or how to 
> solve it?
> 

Cannot reproduce it here.  It works perfectly.  Toolchain bug?

Lee


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Re: hw_params from shared library problem

[Benoit Fouet]

Hi,

Gerald Grabner wrote:

>Hi everybody,
>
>I'm wondering how to correctly build a shared library using alsa
>pcm. Setting the hardware parameters in a function which is part of a
>shared library produces an error, snd_pcm_hw_params gives "invalid
>argument". The example below with three primitive files (main file,
>header and function code) illustrates the problem. With a static
>library, everything works fine.
>
>My system: gcc 3.4.6 on Gentoo with alsa 1.0.11.
>
>Does anybody have an idea about the cause of this problem or how to 
>solve it?
>
>Many thanks,
>Gerald
>
>***
>
>main.c:
>   #include "object.h"
>   int main()
>   {
>     object () ;
>     return 0;
>   }
>
>object.h:
>   void object();
>
>object.c:
>   #include <alsa/asoundlib.h>
>   #include "object.h"
>   void object ()
>   {
>     snd_pcm_t* pcm;
>     snd_pcm_hw_params_t* hwparams;
>     int rc;
>     unsigned int rate = 44100;
>     unsigned int channels = 2;
>     int dir = 0;
>     if ( snd_pcm_open(&pcm, "default", SND_PCM_STREAM_PLAYBACK, 0) < 0 )
>       printf("Cannot open pcm.\n");
>     snd_pcm_hw_params_alloca(&hwparams);
>     snd_pcm_hw_params_any(pcm, hwparams);
>     snd_pcm_hw_params_set_access(pcm, hwparams, 
>SND_PCM_ACCESS_RW_INTERLEAVED);
>     snd_pcm_hw_params_set_format(pcm, hwparams, SND_PCM_FORMAT_S16_LE);
>     snd_pcm_hw_params_set_channels (pcm, hwparams, channels);
>     snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, &dir);
>     rc = snd_pcm_hw_params(pcm, hwparams) ;
>     if ( rc < 0 )
>       printf("Error setting hw params: %s.\n", snd_strerror(rc));
>   }
>
>Compilation:
>   gcc -c -fPIC object.c
>   gcc -shared -fPIC -o libTest.so object.o
>   gcc -o main main.c -L. -lTest -lasound
>  
>
and what if you try to link your dynamic library with asound (actually,
this is the really needer of the link, not your test program) ? I think
this could help...

gcc -shared -fPIC -o libTest.so object.o -lasound

-- Ben

>Output:
>   Error setting hw params: Invalid argument.
>
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>_______________________________________________
>Alsa-devel mailing list
>Alsa-devel@lists.sourceforge.net
>https://lists.sourceforge.net/lists/listinfo/alsa-devel
>  
>

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Re: hw_params from shared library problem

[Gerald Grabner]

Benoit Fouet wrote:

 >> Compilation:
 >>   gcc -c -fPIC object.c
 >>   gcc -shared -fPIC -o libTest.so object.o
 >>   gcc -o main main.c -L. -lTest -lasound
 >>
 >>
 > and what if you try to link your dynamic library with asound (actually,
 > this is the really needer of the link, not your test program) ? I think
 > this could help...
 >
 > gcc -shared -fPIC -o libTest.so object.o -lasound

Hey, thanks a lot, that did the trick!

Interestingly, other libraries I am using do not require to be specified 
when building the shared library.

Gerald

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Re: hw_params from shared library problem

[Takashi Iwai]

At Tue, 27 Jun 2006 19:08:57 +0200,
Gerald Grabner wrote:
> 
> Benoit Fouet wrote:
> 
>  >> Compilation:
>  >>   gcc -c -fPIC object.c
>  >>   gcc -shared -fPIC -o libTest.so object.o
>  >>   gcc -o main main.c -L. -lTest -lasound
>  >>
>  >>
>  > and what if you try to link your dynamic library with asound (actually,
>  > this is the really needer of the link, not your test program) ? I think
>  > this could help...
>  >
>  > gcc -shared -fPIC -o libTest.so object.o -lasound
> 
> Hey, thanks a lot, that did the trick!
> 
> Interestingly, other libraries I am using do not require to be specified 
> when building the shared library.

It's most likely due to versioned symbols used in alsa-lib.


Takashi

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