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From Aaron Bannert <>
Subject Re: Problem compiling mod_webapp for IBM HTTP Server 1.9.19 running on AIX 4.3.3. Please help save Tomcat for a high profile project in Switzerland
Date Sun, 18 Nov 2001 20:04:12 GMT
Lurking indeed... ;)

On Sun, Nov 18, 2001 at 10:34:42AM -0800, Justin Erenkrantz wrote:
> On Sat, Nov 17, 2001 at 08:51:24PM +0100, wrote:
> > First of all I attempt to calmly summarize the problem and only then let my emotions
get through. 

You're certainly not the first to be frustrated by this problem. :)

> > My insufficient knowledge of AIX platforms prevents me from successfully compiling
mod_webapp (as well mod_jk) on AIX 4.3.3 platform.
> >  
> > Tomcat itself appears to be running flawlessly. Unfortunately due to my meager knowledge
of AIX I seem to be unable to recompile neither mod_webapp nor mod_jk for the specified platform.
Actually compilation worked fine in both cases. What did fail was the ‘ld’ linker. As far
as I can judge about possible cause of failure, the linker requires a module export (.exp)
file in order to be able successfully complete linking process. In this respect AIX appears
to differ from Unixes, as I had no problems at all building mod_webapp & mod_jk under
Linux (Mandrake 8.0 & Mandrake 8.1) as well as Solaris 8. The problem is aggravated by
the management’s desire to use IBM HTTP Server instead of plain Apache mainly due to IBM’s
SSL support, which is perceived to be more trustworthy and secure. 
> > 
> > Is my assumption right? If yes, is there a way I could generate that damn .exp file
for mod_webapp? I could also live with mod_jk as a fallback scenario. 

> I know that Aaron Bannert spent some time working with the IBM
> httpd folks (Victor, Greg, Bill, Jeff, etc.) trying to get AIX DSO 
> support for Apache 2.0 and APR.  I believe the eventual conclusion 
> from the IBM AIX gurus in Austin was that the linker is not capable 
> of handling external dependencies in an acceptable manner.  Their
> recommendation was to wait for the next major release of AIX which 
> would have a new linker.  But, this isn't very helpful to you or 
> to us httpd folks though.

As of yet we have not been able to tame the beast that is the AIX linker
WRT apache-2.0 and DSOs. The essential problem has to do with the mechanism
used at runtime to load and dynamically link modules, and the aparent
inability of the AIX linker to deal with interdependent shared objects.

In the short term this really only applies to apache-2.0 and modules
that automatically depend on other libraries, like how mod_webapp depends
on libapr and libaprutil. The problem in this scenario is that libaprutil
actually depends on symbols exported from libapr. First-order runtime
linkages seem to work fine, but as soon as you hit a symbol that depends
on that second library (even if they are statically linked into the same
shared object) you'll get a segfault. It's entirely possible that over
in httpd-2.0 we're doing something wrong, but given the number of people
looking at this issue, that is becomming less and less likely.

> > I have been informed by the management that if problem is not resolved by mid next
week Tomcat will be replaced with WebSphere 3.5 Standard Edition. 

My first impression to this post was to suggest you contact your vendor
for a solution. (My second and more emotionally based response was to
suggest you change operating systems. ;)

Hope that provides some insight,

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