cannot install pg gem, checking for PQconnectdb() in -lpq... no

Question

I'm trying to develop in Ruby on Rails using PostgreSQL locally, so I'm trying to install the pg gem. On Ubuntu 12.04. In terminal, I typed in:

gem install pg -v '0.12.2'

Which throws the following error:

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

        /home/troyshu/.rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb
checking for pg_config... yes
Using config values from /usr/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 ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
    --with-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/home/troyshu/.rvm/rubies/ruby-1.9.3-p194/bin/ruby
    --with-pg
    --without-pg
    --with-pg-dir
    --without-pg-dir
    --with-pg-include
    --without-pg-include=${pg-dir}/include
    --with-pg-lib
    --without-pg-lib=${pg-dir}/lib
    --with-pg-config
    --without-pg-config
    --with-pg_config
    --without-pg_config
    --with-pqlib
    --without-pqlib
    --with-libpqlib
    --without-libpqlib
    --with-ms/libpqlib
    --without-ms/libpqlib


Gem files will remain installed in /home/troyshu/.rvm/gems/ruby-1.9.3-p194/gems/pg-0.14.1 for inspection.
Results logged to /home/troyshu/.rvm/gems/ruby-1.9.3-p194/gems/pg-0.14.1/ext/gem_make.out

Interestingly, adding a sudo to the command works:

$ sudo gem install pg -v '0.12.2'
Building native extensions.  This could take a while...
Successfully installed pg-0.12.2
1 gem installed

Btw I had to run "sudo apt-get install ruby1.9.1-dev" to get the above command to work. But I still can't do any development because "bundle install" will not work (and keeps telling me to run 'gem install pg -v '0.12.2')

I have a feeling "gem install pg" is getting tripped up at

checking for PQconnectdb() in -lpq... no
checking for PQconnectdb() in -llibpq... no
checking for PQconnectdb() in -lms/libpq... no

but, as a complete noob to Ubuntu and RoR, I have no idea why. Maybe my search skills stink too, because I haven't been able to find a solution to my particular case. Hopefully there's a fix?

Thanks!

Answer 1

Related: gem install pg can not bind to libpq. Please check your mkmf log and look for errors with libssl. I had the exact same problem. I had installed libpq-dev and double checked pg_config. It seems that the gem had found the libpq-dev header files but had failed to link with libpq. It turned out that the packages that rvm has installed for ssl were somehow interfering with the packages installed through libssl-dev.