Error Installing ruby gem for PostgreSQL

I am trying to configure a rails server to use PostgreSQL, but getting stuck when installing the postgres gem. I have installed PostgreSQL successfully on the machine (and can use it for other applications) but am getting an error when attempting to install the ruby gem for it.

I do: sudo gem install postgres

And get the following output:

Building native extensions.  This could take a while...
ERROR:  Error installing postgres:
    ERROR: Failed to build gem native extension.

/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby extconf.rb
checking for main() in -lpq... yes
checking for libpq-fe.h... yes
checking for libpq/libpq-fs.h... yes
checking for PQsetClientEncoding()... no
checking for pg_encoding_to_char()... no
checking for PQfreemem()... no
checking for PQserverVersion()... no
checking for PQescapeString()... no
creating Makefile

make
gcc -I. -I. -I/System/Library/Frameworks/Ruby.frame开发者_StackOverflowwork/Versions/1.8/usr/lib/ruby/1.8/universal-darwin10.0 -I. -DHAVE_LIBPQ_FE_H -DHAVE_LIBPQ_LIBPQ_FS_H -I/Library/PostgreSQL/8.4/include  -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE   -fno-common -arch i386 -arch x86_64 -g -Os -pipe -fno-common -DENABLE_DTRACE  -fno-common  -pipe -fno-common   -c libpq-compat.c
libpq-compat.c: In function ‘PQescapeBytea’:
libpq-compat.c:104: warning: incompatible implicit declaration of built-in function ‘sprintf’
libpq-compat.c: In function ‘PQunescapeBytea’:
libpq-compat.c:158: warning: incompatible implicit declaration of built-in function ‘strlen’
libpq-compat.c: In function ‘PQescapeBytea’:
libpq-compat.c:104: warning: incompatible implicit declaration of built-in function ‘sprintf’
libpq-compat.c: In function ‘PQunescapeBytea’:
libpq-compat.c:158: warning: incompatible implicit declaration of built-in function ‘strlen’
gcc -I. -I. -I/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin10.0 -I. -DHAVE_LIBPQ_FE_H -DHAVE_LIBPQ_LIBPQ_FS_H -I/Library/PostgreSQL/8.4/include  -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE   -fno-common -arch i386 -arch x86_64 -g -Os -pipe -fno-common -DENABLE_DTRACE  -fno-common  -pipe -fno-common   -c postgres.c
postgres.c:41: error: static declaration of ‘PQserverVersion’ follows non-static declaration
/Library/PostgreSQL/8.4/include/libpq-fe.h:289: 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:41: error: static declaration of ‘PQserverVersion’ follows non-static declaration
/Library/PostgreSQL/8.4/include/libpq-fe.h:289: 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)
lipo: can't open input file: /var/tmp//ccpTMtE2.out (No such file or directory)
make: *** [postgres.o] Error 1


Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/postgres-0.7.9.2008.01.28 for inspection.
Results logged to /Library/Ruby/Gems/1.8/gems/postgres-0.7.9.2008.01.28/ext/gem_make.out

I am using Mac OS 10.6.4 and Postgres version 8.4.

And idea what could be happening here or how to fix it?

Looks like you're using the EnterpriseDB distribution of Posgres so you need to do this on Snow Leopard:

$ export ARCHFLAGS='-arch i386'
$ sudo gem install pg -- --with-pg-config=/Library/PostgreSQL/8.4/bin/pg_config