C老鸟编程技巧总结 (2)

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5 ，复杂指针的声明

规则总结：

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1） 去掉变量名就类型 , 去掉一个 *, 就是指向内存单元的类型 .

2） 强调什么将名子和强调的东东括最里层 , 再将其次强调的东西括外面一层 , 最后强调的括最外层 , 类型最后加在外面 :

如 : int (*i)[2]; 指向 int ()[2] 的指针 ( 强调指针 )

Int *(i[2]); 类型为 int *() 的数组 ( 强调数组 )

Void (*pf)(); 指向 void ()() 的函数指针 .

Void (*(pf[2]))(); 函数类型为 void ()() 的指针数组 ( 最强调数组 , 所以先括数组 , 其次强调指针 , 所以将它括在外面一层 .

Void (*((*pf)[2]))(); 指向上个函数指针数组的指针 ,( 最强调指针 , 所以将变量明和指针括在最里层 , 其次强调数组 , 所以括在上一层 , 最后又强调指针 , 所以将其括在最外层 .)

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6. 模拟 UCOS 中的 TASK 切换和邮箱机制 （由于 UCOS 代码比较复杂，自己实现了个模拟的，为了方便所以栈还是弄乱了！）

#define T(a,b) t##a(){ \

while(1){ \

printf(gM(a)); \

sM(#b"\n",b); \

mS(); \

} \

}

unsigned int ip=0;

char mb[2][3];

char*gM(int p){

return (mb[p-1]);

}

sM(char*m,int p){

strcpy(mb[p-1],m);

}

mS(){

Sleep(0xFF);

_asm mov eax,ip

_asm xchg eax,[ebp+4]

_asm mov ip,eax

}

T(1,2)

T(2,1)

main(){

ip=&t2;

t1();

}

7, 泛型宏 （说明代码提取自 Linux 源码）

#define min(x, y) ({ \

typeof(x) _min1 = (x); \

typeof(y) _min2 = (y); \

(void) (&_min1 == &_min2); \

_min1 < _min2 ? _min1 : _min2; })