[Haskell-cafe] Re: Problems installing HDBC-postgresql

[John Goerzen]

On 2006-07-10, Martin Percossi <haskell-cafe at martinpercossi.com> wrote:
> Hi, I'm having problems using HDBC-postgresql (I've tried both 0.99.2.1 
> and 1.0.0.0) with postgresql (version 8.1.4, installed in /share/pgsql). 
> I adjust the include-dir and extra-lib-dirs to use the custom location 
> of postgresql, and build: no error messages, everything seems fine.

Probably, though, there is something that is not quite fine...

> However, when I then try to type:
> ghci -package HDBC -package HDBC-postgresql
> , I get the error message:
> Loading package HDBC-postgresql-0.99.2.1 ... linking ... ghc-6.4.2: 
> /home/mpercossi/opt/lib/HDBC-postgresql-0.99.2.1/HSHDBC-postgresql-0.99.2.1.o: 
> unknown symbol `PQserverVersion'
> ghc-6.4.2: unable to load package `HDBC-postgresql-0.99.2.1'

This sounds like it's not finding your PostgreSQL libraries.

First, can you confirm that PQserverVersion still occurs in your
libpq-fe.h?

Next, try strace on your ghci session.

Grep for libpq in the output.  It may be instructive.

In my case, I saw:

stat64("/usr/lib/haskell-packages/ghc6/lib/HDBC-postgresql-0.99.2.1/libpq_dyn.so",
0xb763a1e0) = -1 ENOENT (No such file or directory)
stat64("/usr/lib/haskell-packages/ghc6/lib/HDBC-postgresql-0.99.2.1/libpq.so",
0xb763a570) = -1 ENOENT (No such file or directory)
open("/usr/lib/libpq.so", O_RDONLY)     = 3

So we know that the system did successfully open that library.

> Has anyone seen this error message before? Google didn't turn up 
> anything relevant to haskell -- however there does seem to be a 
> PQserverVersion procedure in the libpq library -- maybe HDBC-postgresql 
> is not seeing this due to the custom install location?

This would all be up to your modifications to cabal.  

Try: ghc-pkg describe HDBC-postgresql

You should see:

 * pq in the extra-libraries line
 * Your header file location in the include-dirs line
 * Your extra-lib-dirs path

If you don't see those things, then something went wrong with the build
or install.

I would also suggesting building a program with GHC (not GHCI) that uses
HDBC-postgresql for testing.

-- John