Ruby on rails 未能生成gem本机扩展-解决方案

当我安装gem

时，它会失败，出现错误

错误：无法构建gem本机扩展。

例如，当我尝试在新服务器上安装gems-json、eventmachine、mysql2时，几乎总是失败

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注意：这是一个QA类型的问题，也就是说，请参阅下面我提出的解决方案或加入讨论。

此错误通常发生在新创建的服务器上，因此，该错误自然意味着缺少某些依赖项

“转折点”是，错误本身通常会告诉我们缺少哪些依赖项，但我们浏览了一下描述，并尝试谷歌“未能构建gem…”。最好先检查错误输出

例如，在尝试在新机器上安装gem'json'时，让我们看看输出：

user@server:~$ gem install json -v '1.8.3'
Fetching: json-1.8.3.gem (100%)
Building native extensions.  This could take a while...
ERROR:  Error installing json:
    ERROR: Failed to build gem native extension.

    .../.rvm/rubies/ruby-2.2.2/bin/ruby -r ./siteconf20151204-22068-1ek4f2f.rb extconf.rb
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling generator.c
linking shared-object json/ext/generator.so
/usr/bin/ld: cannot find -lgmp
collect2: error: ld returned 1 exit status
make: *** [generator.so] Error 1

make failed, exit code 2

Gem files will remain installed in .../.rvm/gems/ruby-2.2.2/gems/json-1.8.3 for inspection.
Results logged to .../.rvm/gems/ruby-2.2.2/extensions/x86_64-linux/2.2.0/json-1.8.3/gem_make.out

检查错误后，您可以看到缺少的内容：

/usr/bin/ld: cannot find -lgmp

那么什么是lgmp？让我描述一下我的尝试和错误的道路，同时找出它。在谷歌搜索了一会儿后，我发现

lgmp

中的

l

代表库，而GMP是一个尚未安装在我的机器上的C库。我的下一个谷歌查询是“安装gmp ubuntu”，这让我安装了libgmp3 dev，问题就解决了

现在，让我们看看在新服务器上安装mysql2时的输出：

user@server:~$ gem install mysql2 -v '0.3.20'
Fetching: mysql2-0.3.20.gem (100%)
Building native extensions.  This could take a while...
ERROR:  Error installing mysql2:
    ERROR: Failed to build gem native extension.

    .../.rvm/rubies/ruby-2.2.2/bin/ruby -r ./siteconf20151204-9782-1eobqf2.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
checking for mysql_query() in -lmysqlclient... no
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libmysqlclient is missing. Trying again with extra runtime libraries...
-----
checking for main() in -lm... yes
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lz... yes
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lsocket... no
checking for main() in -lnsl... yes
checking for mysql_query() in -lmysqlclient... no
checking for main() in -lmygcc... no
-----
libmysqlclient is missing. You may need to 'apt-get install libmysqlclient-dev' or 'yum install mysql-devel', and try again.
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*** 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.
# SNIP

同样，在仔细查看时，您可以看到

libmysqlclient丢失了

，该错误甚至提供了最明显的解决方案：

您可能需要“apt get install libmysqlclient dev”或“yum install mysql devel”，然后重试。

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我希望这将帮助开发人员更快地解决此类错误，而不必为每一个特定的gem故障（通常不会带来任何结果）搜索谷歌。

您可以到终端并将其写下来

sudo apt get install libmysqlclient dev

我希望这对你有帮助