M2Crypto安装方法以及配置LDFLAGS、CFLAGS

python3.7+mac环境：

$ brew install openssl && brew install swig
$ brew --prefix openssl
/usr/local/opt/openssl
$ LDFLAGS="-L$(brew --prefix openssl)/lib" 
CFLAGS="-I$(brew --prefix openssl)/include" 
SWIG_FEATURES="-I$(brew --prefix openssl)/include" 
pip install m2crypto

关于swig的作用

　　SWIG is an interface compiler that connects programs written in C and C++ with scripting languages such as Perl, Python, Ruby, and Tcl. It works by taking the declarations found in C/C++ header files and using them to generate the wrapper code that scripting languages need to access the underlying C/C++ code. In addition, SWIG provides a variety of customization features that let you tailor the wrapping process to suit your application

CFLAGS与LDFLAGS

CFLAGS的选项-I ： 用于把新目录添加到include路径上，可以使用相对和绝对路径，“-I.”、“-I./include”、“-I/opt/include”

LDFLAGS的选项-L：用于把新目录添加到库搜索路径上，可以使用相对和绝对路径，“-L.”、“-L./include”、“-L/opt/include”

Makefile 选项 CFLAGS 、LDFLAGS 、LIBS

CFLAGS 表示用于C编译器的选项
CXXFLAGS 表示用于C++编译器的选项
这两个变量实际上涵盖了编译和汇编的两个步骤

CFLAGS：指定头文件(.h)的路径，如：CFLAGS=-I/usr/include -I/path/include 。

相同地，安装一个包时会在安装路径下建立一个include文件夹，当安装过程中出现故障时，试着把曾经安装的包的include文件夹增加到该变量中来。

LDFLAGS：gcc 等编译器会用到的一些优化參数，也能够在里面指定库文件的位置。使用方法：LDFLAGS=-L/usr/lib -L/path/to/your/lib。每安装一个包都一定会在安装文件夹里建立一个lib文件夹

LIBS：告诉链接器要链接哪些库文件。如LIBS = -lpthread -liconv

简单地说，LDFLAGS是告诉链接器从哪里寻找库文件，而LIBS是告诉链接器要链接哪些库文件。

参考：

http://www.swig.org/exec.html

https://gitlab.com/m2crypto/m2crypto/blob/master/INSTALL.rst#macosx

https://blog.csdn.net/zhaoyun_zzz/article/details/82466031

https://www.cnblogs.com/lytwajue/p/7161742.html