Roy's Techblog

Unfortunately, out of the box, the postgres gem fails to install with the MacPorts postgres82-server install. There are two problems. The first is it can’t find pg_config. The second is incorrect architecture detection (thanks to Andreas Flierl at the RubyForge postgres module forums for pointing out the fix).

ERROR:  Error installing postgres:
    ERROR: Failed to build gem native extension.

/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb install postgres
extconf.rb:73: command not found: pg_config --bindir

The fix for this one is to fix the path temporarily:

 export PATH=/opt/local/lib/postgresql82/bin/:$PATH

Then when we retry the gem installation, we’ll get the following error(s):

postgres.c:41: error: static declaration of ‘PQserverVersion’ follows non-static declaration
/opt/local/include/postgresql82/libpq-fe.h:262: error: previous declaration of ‘PQserverVersion’ was here
postgres.c:41: error: static declaration of ‘PQserverVersion’ follows non-static declaration
/opt/local/include/postgresql82/libpq-fe.h:262: error: previous declaration of ‘PQserverVersion’ was here
postgres.c: In function ‘Init_postgres’:
postgres.c:2676: error: ‘pgconn_protocol_version’ undeclared (first use in this function)
postgres.c:2676: error: (Each undeclared identifier is reported only once
postgres.c:2676: error: for each function it appears in.)
postgres.c:2677: error: ‘pgconn_server_version’ undeclared (first use in this function)
postgres.c: In function ‘Init_postgres’:
postgres.c:2676: error: ‘pgconn_protocol_version’ undeclared (first use in this function)
postgres.c:2676: error: (Each undeclared identifier is reported only once
postgres.c:2676: error: for each function it appears in.)
postgres.c:2677: error: ‘pgconn_server_version’ undeclared (first use in this function)
lipo: can't open input file: /var/tmp//ccBatpen.out (No such file or directory)
make: *** [postgres.o] Error 1

These are fixed by specifying a specific architecture to use.

The following commands worked well for me:

export PATH=/opt/local/lib/postgresql82/bin/:$PATH
sudo env ARCHFLAGS="-arch i386" gem install --remote postgres