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From "Janek Bogucki" <...@purpleturtle.com>
Subject Solution to mod_webapp.so:undefined symbol: pthread_sigmask on Red Hat Linux 7.1
Date Sat, 22 Sep 2001 01:11:29 GMT
Hi,

I may have solved (or at least worked around) the the missing
'pthread_sigmask' symbol error encountered when trying to use
mod_webapp.so. From the mailing list it appears to affect this
configuration:

   1. Red Hat Linux 7.1

   2. Apache 1.3.x
   
   3. httpd.conf will have these lines in it:

         LoadModule webapp_module      libexec/mod_webapp.so
         AddModule mod_webapp.c

The symptom is this:

    [root@bogucki bin]# ./apachectl start
    Syntax error on line 241 of /opt/apache/conf/httpd.conf:
    Cannot load /opt/apache/libexec/mod_webapp.so into server:
          /opt/apache/libexec/mod_webapp.so: undefined symbol:
          pthread_sigmask
    ./apachectl start: httpd could not be started
    [root@bogucki bin]# 

The solution is:

    [root@bogucki bin]# export LD_PRELOAD=/lib/i686/libpthread-0.9.so
    [root@bogucki bin]# ./apachectl start
    ./apachectl start: httpd started
    [root@bogucki bin]# 

I am cautious in my proposal of this as the 'solution' as I'm
unaware of any ill side-effects this may have. I have not yet
tested mod_webapp.so now that finally I have httpd up with
mod_webapp.so. I'm saving that for later :-)

----------------------------------------

It might be useful if I describe the path I took to get to this
solution:


Step 1.

I located all libpthread.so's on my system:

    [root@bogucki conf]# locate libpthread.so
    /usr/lib/libpthread.so
    /lib/i686/libpthread.so.0
    /lib/libpthread.so.0
    [root@bogucki conf]# 

These are symbolic links pointing to these libraries:

    /lib/i686/libpthread-0.9.so
    /lib/libpthread-0.9.so

Step 2.

I listed the symbols in each, looking for 'pthread_sigmask':

    
    [root@bogucki conf]# nm /lib/libpthread-0.9.so 
    nm: /lib/libpthread-0.9.so: no symbols
    [root@bogucki conf]# 
    
    [root@bogucki conf]# nm /lib/i686/libpthread-0.9.so |wc
        501    1409   15588
    [root@bogucki conf]# nm /lib/i686/libpthread-0.9.so |grep sigmask
    00009640 T pthread_sigmask
    [root@bogucki conf]#

(Why would a library not have any symbols? Anyone know?)

Step 3.

I forced the preloading of the library with symbols in via
LD_PRELOAD and httpd started and served out on http://127.0.0.1 okay.

----------------------------------------

I would be interested to hear if this works for anyone else and
if any weirdnesses can be expected as a result of this
workaround.

all the best,
yan


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