Errors when installing cocoapods with gem

Question

I am using macOS Mojave and when I try to install cocoapods using gem I am getting the following error.

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

current directory: /Library/Ruby/Gems/2.3.0/gems/ffi-1.12.2/ext/ffi_c 

/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/bin/ruby -r ./siteconf20200302-707-1iveybq.rb extconf.rb mkmf.rb can't find header files for ruby at /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/include/ruby.h

extconf failed, exit code 1

Gem files will remain installed in /Library/Ruby/Gems/2.3.0/gems/ffi-1.12.2 for inspection. Results logged to /Library/Ruby/Gems/2.3.0/extensions/universal-darwin-18/2.3.0/ffi-1.12.2/gem_make.out

This error comes when I run the following commands.

sudo gem install cocoapods  sudo gem install -n /usr/local/bin cocoapods 

I have already installed xcode command line tools and I get the following message when I run xcode-select --install

xcode-select: error: command line tools are already installed, use "Software Update" to install updates

I have also agreed to xcode license agreements with the command sudo xcodebuild -license

The error log in /Library/Ruby/Gems/2.3.0/extensions/universal-darwin-18/2.3.0/ffi-1.12.2/gem_make.out gives the following

current directory: /Library/Ruby/Gems/2.3.0/gems/ffi-1.12.2/ext/ffi_c /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/bin/ruby -r ./siteco$ mkmf.rb can't find header files for ruby at /System/Library/Frameworks/Ruby.fra$

extconf failed, exit code 1

What do I do to fix this issue ?

Answer 1

The answer for this can be found here here although it is unrelated to this question. Below is a snippet of the answer which works best.

For Xcode 11 on macOS 10.14, this can happen even after installing Xcode and installing command-line tools and accepting the license with

sudo xcode-select --install sudo xcodebuild -license accept 

The issue is that Xcode 11 ships the macOS 10.15 SDK which includes headers for ruby2.6, but not for macOS 10.14's ruby2.3. You can verify that this is your problem by running

ruby -rrbconfig -e 'puts RbConfig::CONFIG["rubyhdrdir"]' 

which on macOS 10.14 with Xcode 11 prints the non-existent path

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/include/ruby-2.3.0 

However, Xcode 11 installs a macOS 10.14 SDK within /Library/Developer/CommandLineTools/SDKs/MacOS10.14.sdk. It isn't necessary to pollute the system directories by installing the old header files as suggested in other answers. Instead, by selecting that SDK, the appropriate ruby2.3 headers will be found:

sudo xcode-select --switch /Library/Developer/CommandLineTools ruby -rrbconfig -e 'puts RbConfig::CONFIG["rubyhdrdir"]' 

This should now correctly print

/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/include/ruby-2.3.0 

Likewise, gem install should work while that SDK is selected.

To switch back to using the current Xcode 11 SDK, use

sudo xcode-select --switch /Applications/Xcode.app 

Answer 2

For me use a command sudo gem install cocoapods -v 1.8.4 instead of sudo gem install cocoapods

Reference: https://github.com/CocoaPods/CocoaPods/issues/9568#issuecomment-599235420