Difference between -shared, -symbolic, and -G?

[Todd]

Andrew Haley wrote:
>> I am using gcc version 4.3.3 for x86
>>
>> -Wl,-Bsymbolic looks like it does what I want.
>
> Be very, very careful.  -Bsymbolic violates the C standard, and all
> manner of very weird things can happen to your program.  One symptom
> is that data in a shared library that is written by an executable
> fails mysteriously to be there when read by the library.  This is
> because you end up with two copies of the data, one in the shared
> library and one in the executable, even though the data is only
> defined once in the library.  It is possible to solve most of these
> problems by compiling the executable as PIC.
>
> Andrew.
>

Hmm. I just need to have a function in my shared library, callable from 
the executable linked against the shared library, which I can also call 
from inside the shared library such that calls originating inside always 
invoke the one defined inside. What is the right way to achieve this, then?

-Todd