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From <oh...@cox.net>
Subject Re: UNSOLVED was Re: SOLVED was Re: How to compiling/link/use Apache module that uses shared library?
Date Fri, 22 Jun 2012 00:56:54 GMT

---- ohaya@cox.net wrote: 
> 
> ---- Joe Lewis <joe@joe-lewis.com> wrote: 
> > On 6/21/12 5:49 PM, ohaya@cox.net wrote:
> > > ---- ohaya@cox.net wrote:
> > >> ---- Sorin Manolache<sorinm@gmail.com>  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
in
> > >>> emacs and let emacs do the nice listing of source code in a different
panel.
> > >>>
> > >>> 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/ld.so.conf.d/my.conf, and added the directory where my libobaccess.so
was
> > > - 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/ld.so.conf.d files provide additional search directories for the 
> > linker to check in when loading a library.
> > 
> > Joe
> > --
> > http://www.silverhawk.net/
> 
> 
> 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 libobaccess.so 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/mod_headers.so
into server: /apps/httpd2222/modules/mod_headers.so: undefined symbol: ObResource_isProtected
> 
> That "ObResource_isProtected" should be a symbol in libobaccess.so, and in fact, if I
do "nm --dynamic", I get:
> 
> [root@apachemodule build-mod_headers]# nm --dynamic /apps/netpoint/lib64/libobaccess.so
| 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 libobaccess.so
is actually not being loaded, but then when I try to load libobaccess.so, 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
> 
> 

Hi,

Also, BTW, now that I have the ld.so.conf.d setup, I can do "ldconfig -p" and get:

[root@apachemodule build-mod_headers]# ldconfig -p | grep libob
        libobaccess.so (libc6,x86-64) => /apps/netpoint/lib64/libobaccess.so

The library TYPE ("libc6") is the same with other .so files that are use, e.g., the libssl*.so,
when I list them with ldconfig.

Sill don't understand why loading that libobaccess.so causes Apache to segfault :(...

Jim

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