Error installing Postgres gem on Mac - ruby-on-rails

Question

Here's the error I get when I run gem install pg:
ERROR: Error installing pg:
ERROR: Failed to build gem native extension.
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby -r ./siteconf20151004-5579-1t2l557.rb extconf.rb
checking for pg_config... yes
Using config values from /usr/local/bin/pg_config
checking for libpq-fe.h... yes
checking for libpq/libpq-fs.h... yes
checking for pg_config_manual.h... yes
checking for PQconnectdb() in -lpq... no
checking for PQconnectdb() in -llibpq... no
checking for PQconnectdb() in -lms/libpq... no
Can't find the PostgreSQL client library (libpq)
*** extconf.rb failed ***
If I run brew install postgres I get:
Warning: postgresql-9.4.4 already installed
Likewise, gem list shows pg (0.18.3) and a simple gem -v pg gives:
2.4.4
Running sudo ARCHFLAGS="-arch x86_64" gem install pg returns:
Building native extensions. This could take a while...
Successfully installed pg-0.18.3
invalid options: -f fivefish
(invalid options are ignored)
Parsing documentation for pg-0.18.3
Done installing documentation for pg after 4 seconds
1 gem installed
But bundle install throws up this error:
An error occurred while installing pg (0.18.3), and Bundler cannot continue.
Make sure that `gem install pg -v '0.18.3'` succeeds before bundling.
I'm seeing this in mkmf.log, which I think could be the biggest clue:
ld: warning: ignoring file /opt/local/lib/postgresql93/libpq.dylib, file was built for x86_64 which is not the architecture being linked (i386): /opt/local/lib/postgresql93/libpq.dylib
Undefined symbols for architecture i386:
"_PQconnectdb", referenced from:
_t in conftest-fc6c12.o
ld: symbol(s) not found for architecture i386
Which is strange given file /opt/local/lib/postgresql93/libpq.dylib returns x86_64, not i386:
/opt/local/lib/postgresql93/libpq.dylib: Mach-O 64-bit dynamically linked shared library x86_64
This didn't work either:
sudo env ARCHFLAGS="-arch i386 -arch x86_64" gem install pg

Answer 1

It seems you're almost there, because sudo ARCHFLAGS="-arch x86_64" gem install pg works. Try setting ARCHFLAGS globally, so bundle also can see it:
$ export ARCHFLAGS="-arch x86_64"
$ bundle

Answer 2

I've been working through this issue since yesterday. I ended up uninstalling Postgres, homebrew, and starting from scratch. When trying to add the 'pg' gem to my Ruby on Rail project it kept failing. Digging through the output I kept seeing it try to link the i386 libraries. So I tried adding the flag:
--arch-flags='x86_64'
That didn't seem to have any impact.
Then I found one where it was set right after the 'sudo'. That seemed to do the trick.
THIS WORKED!!!!!!!!
sudo ARCHFLAGS="-arch x86_64" gem install pg -v '0.18.3' -- --with-pg-config=/usr/local/bin/pg_config --arch-flags='x86_64'
In the project I actually had to repeat the steps for some reason in the project directory. Then re-repeat them and upgrade to version 0.18.4.
After that I could run 'bundle' and everything was included correctly.

Answer 3

A couple of the answers here:
http://stackoverflow.com/questions/19625487/impossible-to-install-pg-gem-on-my-mac-with-mavericks
suggest specifying the postgresql configuration file when performing the gem install. It is older but might provide the way forward. Search for "Check you have pg_config in the installed brew", which explains how to find the correct filename.