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From Justin Erenkrantz <jerenkra...@ebuilt.com>
Subject Re: app (Apache) references errno, threads in app use __errno2()
Date Thu, 24 Jan 2002 16:09:04 GMT
On Thu, Jan 24, 2002 at 10:50:43AM -0500, Jeff Trawick wrote:
> The following message is a courtesy copy of an article
> that has been posted to comp.unix.solaris as well.
> 
> I could use some Solaris-specific insight here.
> 
> I suspect that the best situation is that all code is compiled with
> _THREAD_SAFE so that everybody uses __errno2(), but I have a situation
> where that isn't the case and I'm trying to figure out if it is a
> problem.  Here's the situation:
> 
> + Apache 1.3 built with Sun compiler without _THREAD_SAFE
> 
> + module for Apache built with gcc with _THREAD_SAFE; the module
>   creates other threads that run in the Apache processes

I've written an Apache 1.3 module that used threads on Solaris
(the thread usage was implicit behind door calls), so I know
it's fine as long as you play nicely.

Two major gotchas here:

- Apache 1.3 is built with Forte.  Module is built with gcc.
  This almost never works.  I'm shocked it even ran.  mod_webapp
  runs into all sorts of problems when this mismatch occurrs.
  The compilers have different ideas about lots of things, so 
  there could be a mismatch in how errno is handled.

- Building httpd without _THREAD_SAFE with a module compiled for
  _THREAD_SAFE is the root of your problem.  This goes to the 
  discussion Aaron and I had a few days ago about always compiling
  with _REENTRANT/thread-safety flags in httpd-2.0.  I know that
  Solaris goes wonky when this mismatch occurs - it's entirely
  unpredictable - which seems to be what's happening here.

Sorry, but I think Apache 1.3 just needs to be recompiled with
_THREAD_SAFE and with the same compiler as the module.  Anything
else is just asking for trouble like this.  

However, if this error occurs with a _THREAD_SAFE/same-compiler 
build, then it's something we should look into.  I just wouldn't
put any money on that happening.  -- justin


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