https://gcc.gnu.org/onlinedocs/gcc-4.3.2//gcc/Variable-Attributes.html?spm=a2c6h.12873639.0.0.847c2dc5FgohrG#Variable-Attributes
https://developer.aliyun.com/article/1742
https://www.cnblogs.com/sky-heaven/p/8275303.html
https://www.cnblogs.com/amanlikethis/p/3518576.html
http://blog.sina.com.cn/s/blog_679f93560102uzek.html
http://blog.chinaunix.net/uid-20851312-id-3034816.html
https://blog.csdn.net/seven_feifei/article/details/95947358
https://blog.csdn.net/nyist327/article/details/59481809
https://github.com/pvvx/RTL00_AT/blob/master/project/src/user/main.c