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Message-ID: <49D5CC23.8000700@dmi.me.uk>
Date: Fri, 03 Apr 2009 09:43:15 +0100
From: Dave Ingram <dave@dmi.me.uk>
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To: modules-dev@httpd.apache.org
Subject: Re: APR feature detection
References: <49D4F9D1.6040006@dmi.me.uk>
 <20170a030904021159j7e614bfn38ea5a9ca2791b98@mail.gmail.com>
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Sorin Manolache wrote:
> On Thu, Apr 2, 2009 at 19:45, Dave Ingram <dave@dmi.me.uk> wrote:
>   
>> Hi guys,
>>
>> Is there any way that my module can detect which APR features are
>> enabled in Apache? It relies on DBD, and if that's not available then my
>> module just segfaults, which isn't very friendly. I'd prefer to give an
>> error message to the user, telling them that DBD is required.
>>
>> Does anyone have any tips, or should I ask the APR list instead?
>>     
>
> dbd does this:
>     APR_REGISTER_OPTIONAL_FN(ap_dbd_prepare);
>     APR_REGISTER_OPTIONAL_FN(ap_dbd_open);
>     APR_REGISTER_OPTIONAL_FN(ap_dbd_close);
>     APR_REGISTER_OPTIONAL_FN(ap_dbd_acquire);
>     APR_REGISTER_OPTIONAL_FN(ap_dbd_cacquire);
>
> APR_RETRIEVE_OPTIONAL_FN(one of the functions above) should give you
> NULL if DBD is absent.
>
> The two macros are declared in apr_optional.h.
>   

Actually, that's not quite what I was after -- those are defined by
mod_dbd, which I don't rely on (as it's initialised too late for my
module's purposes). I do all of the DBD interaction myself. Is there any
other way to be sure it's enabled? Would:

if (apr_dbd_open != NULL) {
  // error...
}

work?


Dave

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