Re: Conflicting function name in dynamically-loaded shared library

Adam Mackler wrote:
> I am wanting to define some functions as described in section 35.9 of
> the manual, "C-Language Functions." I am compiling pre-existing files
> of c-code from another project into object files, and then linking
> those object files into a shared library along with my own functions
> that follow the posgresql calling convention, invoking other functions
> as desired.
>
> This pre-existing c-code I'm compiling happens to contain a function
> named "point_add()". I see the postgresql source file fmgrtab.c also
> has a function with the same name. When my code tries to invoke its
> version of point_add() I get a bus error, and when I changed the name
> of that function to something else the bus error went away.
>
> Of course, since I'm working with source code I can just keep the
> modified function name, but I would like to be able to keep my version
> of this c code updated with that project and so to use it unmodified.
>
> So my questions are: first, might I be wrong about the cause of this
> bus error? I cannot think of another reason why changing the name of
> a function would have this effect, but maybe there's some other reason
> besides the "point_add()" function in fmgrtab.c conflicting. If so,
> I'm interested to know.
>
> If, however, it is probable that this bus error is a result of this
> naming conflict, then do I have any options for working around it that
> would enable me to use the code from this other library without
> changing the name of its "point_add()" function? I know I could ask
> that project's developers to change the function's name, but that
> could break other code that currently uses it, and even if it didn't,
> I would prefer something less intrusive on that project.

If you are on Linux, you could try the following patch:

http://www.postgresql.org/message-id/CA+CSw_tPDYgnzCYW0S4oU0mTUoUhZ9pc7MRBPXVD-3Zbiwni9w@mail.gmail.com

Maybe that will make it work, then you know that your suspicion was correct.

But what you describe should definitely cause a problem, though
"bus error" sounds surprising to me.

Renaming one of the functions seems like the best thing to do.
It would need a convincing case (like, many people have that problem)
to get the name changed in PostgreSQL.

Yours,
Laurenz Albe