Conflicting function name in dynamically-loaded shared library

From: Adam Mackler <pgsql-general(at)mackler(dot)org>
To: pgsql-general(at)postgresql(dot)org
Subject: Conflicting function name in dynamically-loaded shared library
Date: 2015-01-28 04:06:30
Message-ID: 20150128040630.GA43952@scruffle.mackler.org
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Hi:

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.

Thanks very much for any ideas about this,
--
Adam Mackler

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