macOS Mojave で ld: library not found と怒られる時

背景

  • gem install mysql2 がコケる
  • MySQL 自体は brewmysql@5.7 をインストールしている
  • xcode-select —install で XCode command line tools はインストールしてあることを確認済

現象

以下のように、 ld: library not found for -lssl というライブラリ周りのエラーが発生する:

$ gem install mysql2
Building native extensions.  This could take a while...
ERROR:  Error installing mysql2:
    ERROR: Failed to build gem native extension.

    current directory: /Users/alea12/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/mysql2-0.5.2/ext/mysql2
/Users/alea12/.rbenv/versions/2.4.3/bin/ruby -r ./siteconf20181026-7734-1e6eqmp.rb extconf.rb
checking for rb_absint_size()... yes
checking for rb_absint_singlebit_p()... yes
checking for rb_wait_for_single_fd()... yes
-----
Using mysql_config at /usr/local/opt/mysql@5.7/bin/mysql_config
-----
checking for mysql.h... yes
checking for errmsg.h... yes
checking for SSL_MODE_DISABLED in mysql.h... yes
checking for SSL_MODE_PREFERRED in mysql.h... yes
checking for SSL_MODE_REQUIRED in mysql.h... yes
checking for SSL_MODE_VERIFY_CA in mysql.h... yes
checking for SSL_MODE_VERIFY_IDENTITY in mysql.h... yes
checking for MYSQL.net.vio in mysql.h... yes
checking for MYSQL.net.pvio in mysql.h... no
checking for MYSQL_ENABLE_CLEARTEXT_PLUGIN in mysql.h... yes
checking for SERVER_QUERY_NO_GOOD_INDEX_USED in mysql.h... yes
checking for SERVER_QUERY_NO_INDEX_USED in mysql.h... yes
checking for SERVER_QUERY_WAS_SLOW in mysql.h... yes
checking for MYSQL_OPTION_MULTI_STATEMENTS_ON in mysql.h... yes
checking for MYSQL_OPTION_MULTI_STATEMENTS_OFF in mysql.h... yes
checking for my_bool in mysql.h... yes
-----
Don't know how to set rpath on your system, if MySQL libraries are not in path mysql2 may not load
-----
-----
Setting libpath to /usr/local/opt/mysql@5.7/lib
-----
creating Makefile

current directory: /Users/alea12/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/mysql2-0.5.2/ext/mysql2
make "DESTDIR=" clean

current directory: /Users/alea12/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/mysql2-0.5.2/ext/mysql2
make "DESTDIR="
compiling client.c
compiling infile.c
compiling mysql2_ext.c
compiling result.c
compiling statement.c
linking shared-object mysql2/mysql2.bundle
ld: library not found for -lssl
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [mysql2.bundle] Error 1

make failed, exit code 2

Gem files will remain installed in /Users/alea12/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/mysql2-0.5.2 for inspection.
Results logged to /Users/alea12/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/extensions/x86_64-darwin-16/2.4.0-static/mysql2-0.5.2/gem_make.out

対応策

調べていたら Updated to Mojave – Drifting Ruby にたどり着いた。XCode 10 でいろいろなライブラリが削除されてしまったとかなんとか。

/Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg

にある pkg ファイルを Finder から見つけて実行すると良い。

$ gem install mysql2
Building native extensions.  This could take a while...
Successfully installed mysql2-0.5.2
1 gem installed

これでいけた。

macOS Mojave パーフェクトマニュアル

macOS Mojave パーフェクトマニュアル