协程:makecontext参数问题

 

来自云风的协程库：

makecontext(&C->ctx, (void (*)(void)) mainfunc, 2, (uint32_t)ptr, (uint32_t)(ptr>>32));

某makecontext示例代码:

//低版本glibc实现问题不支持64bit指针

     p1 = (uint32_t)((0x00000000FFFFFFFF)&((uint64_t)(&ctx))>>32); //高位

     p2 = (uint32_t)(0x00000000FFFFFFFF&(uint64_t)(&ctx)); //低位

     makecontext(&u, (void(*)(void))(&call_thread), 2, p1, p2);

不理解makecontext为什么一定要传入64位指针; 

后来看makecontext源码 :

 

http://www.oschina.net/code/explore/glibc-2.9/sysdeps/unix/sysv/linux/x86_64/makecontext.c

 

看makecontext源码，发现这一段话：

 

Handle arguments.   www.zzzyk.com 

The standard says the parameters must all be int values. This is 

an historic accident and would be done differently today. For 

x86-64 all integer values are passed as 64-bit values and 

therefore extending the API to copy 64-bit values instead of 

32-bit ints makes sense. It does not break existing 

functionality and it does not violate the standard which says 

that passing non-int values means undefined behavior.

 

 

补充：综合编程 , 其他综合 ,