Mac OS X安装libevent库报Install libevent bufferevent_openssl.c:60:10: fatal error: 'openssl/bio.h' file

编译 libevent（源文件在/Users/carl/Downloads/libevent-2.1.8-stable），执行make命令是，报

Install libevent bufferevent_openssl.c:60:10: fatal error: 'openssl/bio.h' file

第一反应，感觉是不是 openssl版本太低了。

1. 查看openssl版本，发现版本比较低

$ openssl versionOpenSSL 0.9.8zh 14 Jan 2016

2. 升级spenssl，执行

brew install openssl

输出（前面的输出忽略）如下：

==> Downloading https://homebrew.bintray.com/bottles/openssl-1.0.2l.sierra.bottle.tar.gz
######################################################################## 100.0%
==> Pouring openssl-1.0.2l.sierra.bottle.tar.gz
==> Caveats
A CA file has been bootstrapped using certificates from the SystemRoots
keychain. To add additional certificates (e.g. the certificates added in
the System keychain), place .pem files in
  /usr/local/etc/openssl/certs

and run
  /usr/local/opt/openssl/bin/c_rehash

This formula is keg-only, which means it was not symlinked into /usr/local,
because Apple has deprecated use of OpenSSL in favor of its own TLS and crypto libraries.

If you need to have this software first in your PATH run:
  echo 'export PATH="/usr/local/opt/openssl/bin:$PATH"' >> ~/.zshrc

For compilers to find this software you may need to set:
    LDFLAGS:  -L/usr/local/opt/openssl/lib
    CPPFLAGS: -I/usr/local/opt/openssl/include

==> Summary
��  /usr/local/Cellar/openssl/1.0.2l: 1,709 files, 12.2MB

输出以上信息，说明安装成功，安装目录在（/usr/local/Cellar/openssl/1.0.2l）

3. 配置openssl环境变量，指向新安装的openssl

a. 执行 whereis openssl

输出 /usr/bin/openssl

b. 备份原openssl，执行 mv /usr/bin/openssl /usr/bin/openssl_old

c. 创建openssl命令软连接，执行 ln -s /usr/local/Cellar/openssl/1.0.2l/bin/openssl /usr/bin/openssl

d.再执行 openssl version

输出 OpenSSL 1.0.2l  25 May 2017

说明升级成功。

openssl升级成功后，重新编译libevent，执行make名了，还是报Install libevent bufferevent_openssl.c:60:10: fatal error: 'openssl/bio.h' file错误，

于是把新安装的openssl目录的下的头文件 拷贝到libevent源文件目录下，

执行 cp -R /usr/local/Cellar/openssl/1.0.2l/bin/openssl/include    /Users/carl/Downloads/libevent-2.1.8-stable

重新make，编译成功！

参考资料 ：

http://blog.csdn.net/hackcoder/article/details/52442350

http://blog.csdn.net/pz0605/article/details/51954868