Re: Which header and lib files to use when compiling libpq-code?

On Mon, Apr 27, 2009 at 11:10 AM, Martijn van Oosterhout
<kleptog(at)svana(dot)org>wrote:

> On Mon, Apr 27, 2009 at 10:51:45AM -0400, Kynn Jones wrote:
> > I need to compile some code that uses libpq. For this I need to
> determine
> > the directories to use for the header and library files.
> >
> > The machine I'm using has multiple copies of the files libpq-fe.h and
> > libpq.a. How can I determine which one of all these copies are the ones
> > that correspond to the Pg server that is currently running on this
> system?
> > (FWIW, the OS here is Ubuntu Linux.)
>
> In general you don't need to match the server version, the protocol

hasn't changed much in a while so as long as it's less than a few years
> old it'll work.

This statement contradicts the experience I described in my original post:
the choice of header and/or library files is absolutely critical. The wrong
choice lead to very bizarre connection failures.

> > I tried the naive approach of using the "newest" versions of these files,
> as
> > measured by their modification times. This produced disastrous results.
> > The code compiled, but resulted in a program that failed in bizarre and
> > unpredictable ways, which strongly hinted at one or more silent
> segmentation
> > violations in the C code. I conjectured that this was the result of a
> > mismatched header or library file. Sure enough, the bizarre failures
> > disappeared when I used a different set of header and library files.
>
> Given you're using Ubuntu, why not just install postgresql-dev and use
> /usr/include/postgresql.
>

I don't have root privileges on this machine, so I could not install
postgresql-dev, but, as it happens, /usr/include/postgresql already exists
in this machine, in it is, in fact, the version that worked.

But this is not the problem that my question was about. The problem is:
*how to ensure* that the versions of libpq header and library files used for
compiling programs will work properly with a specific Postgres server.

kynn