我正在尝试在我的Mac(High Sierra(上捆绑安装Rails 3.2 LTS应用程序，但是当它到达mysql2 gem时，它失败了：
current directory: /Users/Daniel/.gem/ruby/2.3.5/gems/mysql2-0.3.21/ext/mysql2
/Users/Daniel/.rubies/ruby-2.3.5/bin/ruby -r ./siteconf20180828-30901-1g9qqrc.rb extconf.rb
checking for ruby/thread.h... yes
checking for rb_thread_call_without_gvl() in ruby/thread.h... yes
checking for rb_thread_blocking_region()... no
checking for rb_wait_for_single_fd()... yes
checking for rb_hash_dup()... yes
checking for rb_intern3()... yes
-----
Using mysql_config at /usr/local/bin/mysql_config
-----
checking for mysql.h... yes
checking for errmsg.h... yes
checking for mysqld_error.h... yes
-----
Setting rpath to /usr/local/Cellar/mysql/8.0.12/lib
-----
creating Makefile
To see why this extension failed to compile, please check the mkmf.log which can be found here:
/Users/Daniel/.gem/ruby/2.3.5/extensions/x86_64-darwin-16/2.3.0-static/mysql2-0.3.21/mkmf.log
current directory: /Users/Daniel/.gem/ruby/2.3.5/gems/mysql2-0.3.21/ext/mysql2
make "DESTDIR=" clean
current directory: /Users/Daniel/.gem/ruby/2.3.5/gems/mysql2-0.3.21/ext/mysql2
make "DESTDIR="
compiling client.c
client.c:367:33: warning: implicit conversion loses integer precision: 'long' to 'unsigned int' [-Wshorten-64-to-32]
elapsed_time = end_time - start_time;
~ ~~~~~~~~~^~~~~~~~~~~~
client.c:439:3: error: use of undeclared identifier 'my_bool'
my_bool res = mysql_read_query_result(client);
^
client.c:441:19: error: use of undeclared identifier 'res'
return (void *)(res == 0 ? Qtrue : Qfalse);
^
client.c:762:3: error: use of undeclared identifier 'my_bool'
my_bool boolval;
^
client.c:793:7: error: use of undeclared identifier 'boolval'
boolval = (value == Qfalse ? 0 : 1);
^
client.c:794:17: error: use of undeclared identifier 'boolval'
retval = &boolval;
^
client.c:797:10: error: use of undeclared identifier 'MYSQL_SECURE_AUTH'; did you mean 'MYSQL_DEFAULT_AUTH'?
case MYSQL_SECURE_AUTH:
^~~~~~~~~~~~~~~~~
MYSQL_DEFAULT_AUTH
/usr/local/Cellar/mysql/8.0.12/include/mysql/mysql.h:188:3: note: 'MYSQL_DEFAULT_AUTH' declared here
MYSQL_DEFAULT_AUTH,
^
client.c:798:7: error: use of undeclared identifier 'boolval'
boolval = (value == Qfalse ? 0 : 1);
^
client.c:799:17: error: use of undeclared identifier 'boolval'
retval = &boolval;
^
client.c:830:38: error: use of undeclared identifier 'boolval'
wrapper->reconnect_enabled = boolval;
^
client.c:1152:56: warning: implicit conversion loses integer precision: 'size_t' (aka 'unsigned long') to 'unsigned int' [-Wshorten-64-to-32]
mysql2rb = mysql2_mysql_enc_name_to_rb(charset_name, charset_name_len);
~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~~~~~
client.c:1185:38: error: use of undeclared identifier 'MYSQL_SECURE_AUTH'; did you mean 'MYSQL_DEFAULT_AUTH'?
return _mysql_client_options(self, MYSQL_SECURE_AUTH, value);
^~~~~~~~~~~~~~~~~
MYSQL_DEFAULT_AUTH
/usr/local/Cellar/mysql/8.0.12/include/mysql/mysql.h:188:3: note: 'MYSQL_DEFAULT_AUTH' declared here
MYSQL_DEFAULT_AUTH,
^
2 warnings and 10 errors generated.
make: *** [client.o] Error 1
make failed, exit code 2
我已经尝试了与解决此类问题相关的所有其他技巧，但没有一个奏效，这就是我在这里发布的原因。
更新：
我想我知道问题是什么 - 我在我的机器上运行 mysql 8，但 mysql2 0.3 gem 与此不兼容 - 所以我认为需要一个新问题 - 我如何安装 mysql 5.* 和 mysql8，并让它们中的每一个都与 mysql2 gem 的相关版本一起使用？
我什至需要使用 8，还是可以只使用 5.7 来逃脱？
您现在可能已经找到了答案，但万一没有(或者万一我忘记了并需要再次谷歌搜索(，以下是对我有用的方法：
gem install mysql2 -v '0.3.21' -- --with-opt-dir="$(brew --prefix openssl)"
我正在使用Rails 4.2.11和MySQL服务器版本5.7.24(通过Homebrew安装(