The solution is quite simply. Just make sure pg_config can be [...]]]> I need to fix a project which uses PostgreSQL. On a fresh Leopard install with postgresql 8.3 installed from ports I ran into this problem:

$ sudo gem install pg
Building native extensions.  This could take a while...
ERROR:  Error installing ruby-pg:
ERROR: Failed to build gem native extension.

The solution is quite simply. Just make sure pg_config can be found by the gem installer.

$ mdfind pg_config|grep bin|uniq
/opt/local/lib/postgresql83/bin/pg_config

In this case make sure /opt/local/lib/postgresql/bin is available in the path when executing the gem command

$ PATH=/opt/local/lib/postgresql83/bin:$PATH sudo gem install pg