Event broker, dlopen(), and segfaults

[Ethan Galstad]

While doing some debugging of NDOUtils, I've noticed something bad. 
Event broker modules like ndomod.o will cause Nagios to segfault if they 
are overwritten on the filesystem while they are in use.

I assume this is due to the way dlopen() deals with object files.  I was 
under the assumption that a complete copy of the module was kept in 
memory once it was loaded, but perhaps its mmap()'d.

The segfault is easily reproducible every time I overwrite ndomod.o 
while in use.  Even if the "new" version of the file doesn't differ from 
the old.

Anyone know more details of how this works, or better yet, how to 
avoid/deal with it?


Ethan Galstad,
Nagios Developer
---
Email: nagios at nagios.org
Website: http://www.nagios.org

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