将两个c函数从cpp文件中分离出来单独放入一个c文件中，报了下面的错：
Undefined symbols for architecture armv7:
"MyEncrypt(unsigned char*, int, unsigned char*, int*, unsigned char*)", referenced from:
MainScene::init() in MainScene.o
"MyDecrypt(unsigned char*, int, unsigned char*, unsigned char*)", referenced from:
MainScene::init() in MainScene.o
ld: symbol(s) not found for architecture armv7
clang: error: linker command failed with exit code 1 (use -v to see invocation)
很是抓狂啊，为什么是Undefined symbols for architecture armv7啊？明明还有arm64的。
最后的错误原因感觉跟armv7有点风马牛不相及，其实是很简单的问题，太少写C代码了，居然把这个也忘记了：
If you are using c function in c++ file. you should use extern "c"{}. In .h file
#ifdef __cplusplusextern "C"
{
#endif
swrve_currency_given(parameter1, parameter2, parameter3);// a c function
#ifdef __cplusplus
}
#endif
ld: symbol(s) not found for architecture armv7错误
原文：http://my.oschina.net/u/1443646/blog/360422