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From Joe Lewis <>
Subject Re: UNSOLVED was Re: SOLVED was Re: How to compiling/link/use Apache module that uses shared library?
Date Fri, 22 Jun 2012 00:55:17 GMT
On 6/21/12 6:46 PM, wrote:
> ---- Joe Lewis<>  wrote:
>> On 6/21/12 5:49 PM, wrote:
>>> ---- wrote:
>>>> ---- Sorin Manolache<>   wrote:
>>>>> And I forgot to say: run gdb in some sort of environment where you see
>>>>> your current source code line and a couple of surrounding lines. You
>>>>> could achieve this with the "list" command, but I prefer running gdb
>>>>> emacs and let emacs do the nice listing of source code in a different
>>>>> S
>>>> Here's the function from my source.  It's the original from mod_headers.c,
plus my printf:
>>>> static int header_post_config(apr_pool_t *pconf, apr_pool_t *plog,
>>>>                                 apr_pool_t *ptemp, server_rec *s)
>>>> {
>>>>       printf("In header_post_config\n");
>>>>       header_ssl_lookup = APR_RETRIEVE_OPTIONAL_FN(ssl_var_lookup);
>>>>       return OK;
>>>> }
>>>> Jim
>>> Hi,
>>> I was able to get the segfault to go away.  Here's what I had to do:
>>> - Created /etc/, and added the directory where my
>>> - Run 'ldconfig' to activate.
>>> - In the apxs command, DON'T include the -L and -l arguments
>>> After that, Apache appears to start ok, without segfault :)!!
>>> Thanks for all of the great help, esp. the suggestion about checking "ldconfig
-p".  I still don't understand why, but I'm just glad that I can get past this piece so now
I can debug my module :)...
>>> Later,
>>> Jim
>> I'm just glad this list is as good as it is!
>> FYI, the ldconfig is the dynamic linker control, and those
>> /etc/ files provide additional search directories for the
>> linker to check in when loading a library.
>> Joe
>> --
> Hi,
> Sorry to report, but my earlier report was a "false positive" :)...
> I forgot that the mod_headers.c that I was doing the earlier testing with had all references
to the removed :(!!
> So, I'm still stuck with basically the same problem, now, working with my "full" code,
with the calls in it:
> - If I compile with -L and -l, Apache segfaults when it starts
> - If I compile without -L and -l, then I get "undefined symbol" errors when I try to
start Apache, e.g.:
> [root@apachemodule build-mod_headers]# /apps/httpd2222/bin/apachectl -k start -X
> httpd: Syntax error on line 84 of /apps/httpd2222/conf/httpd.conf: Cannot load /apps/httpd2222/modules/
into server: /apps/httpd2222/modules/ undefined symbol: ObResource_isProtected
> That "ObResource_isProtected" should be a symbol in, and in fact, if I
do "nm --dynamic", I get:
> [root@apachemodule build-mod_headers]# nm --dynamic /apps/netpoint/lib64/
| grep "ObResource_isProtected"
> 00000000000a6d80 T ObResource_isProtected
> [root@apachemodule build-mod_headers]#
> I'm *assuming* that the reason for the "undefined symbol" error is that
is actually not being loaded, but then when I try to load, either via -L and
-l in the apxs, or using LoadFile in httpd.conf, I get the segfault (same gdb info, BTW).
> Catch-22?
> Sorry for the false alarm :(!!
> Jim
Not a catch-22.  The -L and -l specify linker options when assembling 
the code.  The ldconfig is a run-time thing.  If you are getting the 
stderr messages, you are making it all the way into your library.  I'd 
suggest commenting out the following line and see if you get farther :

header_ssl_lookup = APR_RETRIEVE_OPTIONAL_FN(ssl_var_lookup);

That should tell you if the problem is the ssl_var_lookup.


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