[asterisk-dev] Asterisk module compile

[Usman Raza]

Thanks a lot Matthew, i was not sure about snd_spcm_init in
AST_EXT_LIB_CHECK. I managed to resolve my issue through another way, but
this information will definitely be useful to me in the future. I will be
specific with my issues next time.

On Mon, Jul 9, 2012 at 12:29 AM, Matthew Jordan <mjordan at digium.com> wrote:

>
>
> ----- Original Message -----
>
> > From: "Usman Raza" <usman.r123 at gmail.com>
> > To: "Asterisk Developers Mailing List"
> > <asterisk-dev at lists.digium.com>
> > Sent: Sunday, July 8, 2012 12:28:54 PM
> > Subject: Re: [asterisk-dev] Asterisk module compile
>
> > I was unable to load the module due to undefined symbol error on
> > functions i have defined in ringbuffer.h. Following the asterisk
> > build system now, could you tell me about AST_EXT_LIB_CHECK
> > arguments in configure.ac file? Thanks.
>
> I'm not entirely sure what you mean by "tell me about AST_EXT_LIB_CHECK".
>  I'll
> try to explain it as best I can using the ALSA example that the wiki page
> refers
> to, but it may not be applicable to your problem.
>
> If we look at a generated makeopts, we may find the following for ALSA:
>
> ALSA_INCLUDE=
> ALSA_LIB= -lasound -lm -ldl
>
> Those two particular definitions come from makeopts.in, which - if you
> followed
> the wiki - were added previously.  But where did the library checks come
> from?
>
> This is where AST_EXT_LIB_CHECK comes into play.  Going to configure.acand
> searching for ALSA, you'll find the following:
>
> AST_EXT_LIB_CHECK([ALSA], [asound], [snd_spcm_init], [alsa/asoundlib.h],
> [-lm -ldl])
>
> AST_EXT_LIB_CHECK specifies how the configure script will determine if the
> library exists, and, if it does, what additional libraries will be linked
> during
> compilation.  Continuing with the ALSA example, we have the following:
>
> ALSA: The prefix specifier that ties the information in the various build
> system
>       files together
> asound: The actual name of the external library to look for
> snd_spcm_init: A symbol to look for to verify that the library located is
>                correct.  In this case, during execution of the configure
> script,
>                the symbol 'snd_spcm_init' will be looked for in the library
>                'asound'.  If the symbol does not exist, the external
> library
>                check will fail.
> alsa/asoundlib.h: The header files for the library
> -lm -ldl: Optional additional linking flags passed in when the asound
> library is
>           linked
>
> So that explains where ALSA_LIB came from - its the external library to be
> linked (asound), plus the extra linking flags specified in
> AST_EXT_LIB_CHECK
> (-lm -ldl).  If you open a generated configure script, you can walk through
> exactly how it uses these symbols to perform the external library check
> for the
> Advanced Linux Sound Architecture.
>
> Keep in mind that modules with a dependency (in this case, chan_alsa)
> should
> automatically pick up the required compilation include/linking flags when
> they
> are built, by virtue of the generated Menuselect dependency information.
>  You
> obviously need to specify this in the MODULEINFO section for that module,
> as
> the wiki page notes.
>
> I hope this information is useful for you.  Since you haven't asked
> specific
> questions or provided error messages to go on, it very well may not be
> what you
> were looking for.  In the future, when asking questions on the mailing
> list,
> please try to be as specific as possible, including as much information as
> possible.  Otherwise, you may not get the answers you want, if you get an
> answer at all.
>
> Thanks,
>
> --
> Matthew Jordan
> Digium, Inc. | Software Developer
> 445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
> Check us out at: http://digium.com & http://asterisk.org
>
> --
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