I have been trying for some time now to get my Rails development environment back up since I upgraded from Lion to Mountain Lion. The problem is specifically installing the pg-0.14.0 (postgresql) gem.

I have tried the instructions on this post but with no luck. I have tried uninstalling Postgres with Homebrew and then reinstalling it. Nothing is working. If I try to install this gem I recieve this error:

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

/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby 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 * 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.

Where can I find 'mkmf.log'? Can anyone give me a suggestion on how to install the pg gem again?


1 Answer 1


Do you have the Command Line Tools for Xcode installed? These would be required.

Try brew doctor it will diagnose common issues that would affect general compilation issues on Mac.

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