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From Stas Bekman <s...@stason.org>
Subject Re: Symbol resolution problems with aprutil
Date Fri, 21 Mar 2003 00:43:27 GMT
Joe Orton wrote:
> On Mon, Mar 17, 2003 at 07:19:22PM +1100, Stas Bekman wrote:
>>I'm painfully trying to figure out how to resolve all the dependencies of 
>>mod_perl 2.0 on aix. Currently I'm stuck at startup time:
>>Can't load 

>>for module Apache::RequestUtil:     0509-130 Symbol resolution failed for 
>>/usr/local/apache2/lib/libaprutil.so because:
>>        0509-136   Symbol _GLOBAL__FI_libexpat_so (number 108) is not 
>>exported from
>>                   dependent module 
>>        0509-136   Symbol _GLOBAL__FD_libexpat_so (number 109) is not 
>>exported from
>>                   dependent module 
>>        0509-192 Examine .loader section symbols with the
>>                 'dump -Tv' command. at 
>>/usr/local/lib/perl5/5.8.0/aix-thread-multi/DynaLoader.pm line 229.

I haven't worked with aix till a week ago, so I'm learning ropes. All this 
import/export symbols seems too weird to me, but I'm getting there.

> I'd hoped the resident AIX expert would have answered with an easy "do
> this" but he must be distracted :) 

> I have no clue about this particular error, but one thing I'd try would
> be to fix the Makefiles so that libaprutil.so and libapr.so are linked
> against the libraries they are dependent on. e.g. for apr-util, change
> the libtool --mode=link lines and add -lexpat on the end.
> Can you run and link a simple application which links against
> libaprutil.so?

I think I've solved the problem by not importing apr/ap symbols during the 
linking, but instead of using -berok which will ignore unresolved symbols. 
Then things get resolved at run time.

However it seems that apr-util coming with 2.0.44 doesn't export 
apr_generate_random_bytes (I see that fixed in the current apr-util), so I 
have to import that symbol alone. If I import any other symbols I get weird 
segfaults. Go figure.

Any ideas why that causes a problem? Looking at the core traces, I can't see 
any relationships between duplicated import symbols and the segfault. But it 
seems to be the cause: if a library exports symbols and then I import them 
again and link against that library things seem to go wrong.

It's also weird that many times dlopen fails, but dlerror doesn't report 
anything at all.

> Other relevant questions might be: are you on AIX >= 4.3? Are all these
> libraries getting linked with -brtl? Are you using a native CC or gcc?

5.1, CC=cc_r, -brtl.

Looks like I've figured how to get mod_perl 2.0 linked with apr/apr-util work 
now, as long as I manually import only the symbols that were missed out in 
export list by apr/apr-util (in older releases :(

Thanks Joe.

Stas Bekman            JAm_pH ------> Just Another mod_perl Hacker
http://stason.org/     mod_perl Guide ---> http://perl.apache.org
mailto:stas@stason.org http://use.perl.org http://apacheweek.com
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