Question

ucos 里OSTCBFreeList

UCOS 里OS_TCBInit 函数中语句
OS_TCB *ptcb;
ptcb = OSTCBFreeList;
if (ptcb != (OS_TCB *)0) {。。。。。
}
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（OSTCBFreeList是一个地址变量，在void OS_InitTCBList (void)里
for (i = 0; i < (OS_HIGHEST_PRIO + 1); i++) {
OSTCBPrioTbl[i] = (OS_TCB *)0;
}
ptcb1 = &OSTCBTbl[0];
ptcb2 = &OSTCBTbl[1];
for (i = 0; i < (OS_MAX_TASKS + OS_N_SYS_TASKS - 1); i++)
{ ptcb1->OSTCBNext = ptcb2;
ptcb1++;
ptcb2++;
}
ptcb1->OSTCBNext = (OS_TCB *)0;
OSTCBFreeList = &OSTCBTbl[0];
}也就是说OSTCBFreeList是OSTCBTbl[0]的地址，这个地址的数据是(OS_TCB *)0。
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这就不明白ptcb != (OS_TCB *)0究竟是个什么意思了？

Answer 1

把0做了一次强制类型转换，转换成OS_TCB *类型，然后再做判断。