The fact that it is failing on the dlopen() call seems a bit suspect to me. There are a number of things that can go wrong when attempting to open a shared object; but none of them should cause a seg fault.
The one exception I can think of is a problem in the library initialization of the SO. On that basis, I would suggest a few things you could try to get more information.
- Check your library path, and ensure that the library you're trying to load is in this path. (Note: Since you're using Apache, I think you also need to check the library path for the user under which Apache is running. (I think the user is "nobody".) I believe you're looking for the LD_LIBRARY_PATH environment variable.) Also note that if you have multiple versions of the library, this can be really important. Make sure you're loading the correct version of the library.
- As a general debugging principle, try to simplify the problem. Given that I know little about Apache modules, I would try to remove Apache from the equation: Try writing a simple C program that does little more than a dlopen() and possibly the subsequent dlsym(), then exits. This program provides a much simpler environment to troubleshoot and/or debug. If this program runs cleanly, then you may need to look more closely at what's different when the program seg faults. (What's Apache doing differently?) On the other hand, if your program also seg faults, you may consider a potential problem with the library, your compiler switches for the program, and the code in the program. (Or all of the above.)
While I may not have offered very many general purpose debugging tips, I hope something here may have been helpful.
